Cycling of Mineral Nutrients in Agricultural Ecosystems

E II!]rn-E[nsvstems An International Journal sponsored b y the International Association for Ecology

EDITOR-IN-CHIEF:

ASSOCIATE EDITOR:

J.L. Harper University College of North Wales School of Plant Biology Memorial Buildings BANGOR, Caerns N. Wales Great Britain

P. Gruys Research Group for Integrated Pest Control Experimental Orchard "De Schuilenburg" LIENDEN The Netherlands

EDITORIAL ADVISORY BOARD:

M.R. Biswas, Ottawa, Ont., Canada H. Bouwer, Phoenix, Ariz., U.S.A. F. de Soet, Leersum, The Netherlands K.H. Domsch, Braunschwaig-V61kenrode, Federal Republic of Germany E. Frei, Z~Jrich-Reckenholz, Switzerland W.R. Gardner, Madison, Wisc., U.S.A. C.D. Green, Wellesbourne, Great Britain H. Gysin, Basel, Switzerland E.F. Henzell, St. Lucia, QId., Australia L. Hoffmann, Aries, France C.S. Holling, Vancouver, B.C., Canada C.B. Huffaker, Albany, Calif., U.S.A. p. Jacquard, Montpellier, France M. Kassas, Giza, Egypt H.H. Koepf, Dornach, Switzerland B. Lundholm, Stockholm, Sweden D.A. McQuillan, Toronto, Ont., Canada

E.G. Mahn, Halle/S, German Democratic Republic R. Misra, Varanasi, India R.K. Murton, Huntingdon, Great Britain B. Ohnesorge, Stuttgart, Federal Republic of Germany T.A. Rabotnov, Moscow, U.S.S.R. J. Sarukh~n, Mexico, Mexico L. Schmidl, Frankston, Vict., Australia K.F. Schreiber, MiJnster, Federal Republic of Germany C.R.W. Spedding, Reading, Great Britain G. Stanhill, Bet Dagan, Israel J.W. Sturrock, Christchurch, New Zealand L.M. Talbot, Washington, D.C., U.S.A. H.V. Thompson, Guildford, Great Britain B. Ulrich, G~ttingen, Federal Republic of Germany G.J. Vervelde, Wageningen, The Netherlands

V O L U M E 4 (1977/1978)

ELSEVIER S C I E N T I F I C P U B L I S H I N G C O M P A N Y -

AMSTERDAM

vii PREFACE This issue of Agro-Ecosystems contains the o u t c o m e of a symposium on the Cycling of Mineral Nutrients in Agricultural Ecosystems. It was the First International Environmental Symposium of the Koninklijke Nederlandsche Heide Maatschappij (Royal Netherlands Land Development Society), cosponsored by the International Association for Ecology and Elsevier Scientific Publishing Company. The meeting was held on the Elsevier premises in Amsterdam from 31 May to 4 June 1976. An understanding of agricultural ecosystems is regarded as essential to future work in land development. A need was felt to have the subject reviewed by an interdisciplinary group of specialists, also with a view to what directions future research should take. The symposium was of an experimental nature, especially in the way in which it was organised. Background information is given in Annex 1. A number of specialists were invited to write review papers on the cycling of mineral nutrients in agricultural ecosystems, generally covering the geographical region and language area with which they were familiar. In this w a y it was h o p e d that the problem of language barriers, still such a large factor in modern-day scientific communication, might be overcome. The separate reviews were compiled into one integrated general review b y the editor. This integrated review was used as the basis for discussions at a five-day symposium to which the mentioned specialists had been invited. In addition, a number of other experts on this and related fields were asked to take part in the discussions. The integrated review together with the results of the discussions formed the basis of this final report. Certain sections or remarks are based mainly or entirely on the contribution of only one or a few specialists. The name of the specialist(s) is (are) given between brackets indicating that the text is based on his (their) ideas.

Chapter I INTRODUCTION

World population has continued to grow and although some people have been underfed for a b o u t a century now, the increase in the supply of food has managed, in general, to keep pace with this rise thanks to the application of modern agricultural technology. If the growth of the population continues, quite a number of people d o u b t whether.agriculture will be able to feed the increased number of consumers. An important part bf this technology is the use of fertilizers to provide nitrogen, phosphorus and potassium which are elements essential to the growth of living matter (plants and animals}. Fertilizers, particularly those containing nitrogen, require much fossil energy in their manufacture and this is increasingly expensive and, moreover, is a diminishing resource. The raw materials used to make phosphorus and potassium fertilizers have to be mined and although supplies are expected to last many decades the reserves in economically workable concentrations do not have an infinite life. These considerations, plus a greater awareness of the need to protect our environment from the polluting effects of excess fertilizers, and to avoid damage to the physical environment and landscape of our planet, emphasise the need to quantify the movement of nutrients from soils to plant to animals and back to soils again, throughout the world. These transfers of minerals between different types of living matter and parts of the physical environment may be described as nutrient cycles. The principles of nutrient cycling, the mechanisms which control the movement of elements, and their state of balance in parts of systems, or in complete systems, are discussed in Chapters 2 and 3. Before collecting data on nutrient cycles it is necessary to define the scale, or level of organisation of the systems with which we are concerned. Such a level could vary between a distinct plant c o m m u n i t y or field, through areas devoted to a particular crop or product, to whole farm, regional or national levels of organisation. Van Dyne and Abramsky (1975) have described hierarchies of systems in which biological components are involved at all levels of organisation. With increasing complexity, physical c o m p o n e n t s enter at the ecosystem level, economic components at the business level, and social and political components at the regional level. The appropriate level often has to be decided in relation to the social complexity of the society under consideration. The solution chosen in this study, to suit agriculture in as many parts of the world as possible, was to build u p o n a relatively simple unit, the agro-ecosystem, usually represented b y a single farm. Agro-ecosystems and the scheme used to classify the 65 examples described at this symposium are discussed in Chapter 4. In brief, it was assumed that an agricultural ecosystem is an organi-

zation of resources, managed to a greater or lesser extent b y man, with production of human food as one of its main objectives. (The maximization of profit might be regarded by the operator as his main objective). This is a more specific definition than that more usually considered by the ecologist. Tansley (1935) defined an ecosystem as "an area within which the processes of primary production, consumption, decomposition and recirculation are largely self-contained". It is usually accepted that a recognisable vegetation/soil complex represents an ecosystem unit but, given the mobility of large herbivores, a grazed rangeland containing several vegetation/soil units may also be considered a basic unit. Because of the transport of nutrients b y water a defined catchment area could also be regarded as a logical unit. The nutrient cycling pools and pathways (or model) and the design and format of the tables used as the template for collecting all the data for the cycles of nitrogen, phosphorus and potassium in a wide range of contrasted agro-ecosystems, are described in Chapter 5. The main b o d y of the report (Chapter 6) consists of nutrient cycling data from a b o u t 65 agro-ecosystems which are described in detail b y their authors. Some of the latter have discussed the conclusions which arise from consideration of the data for all their own systems and their views are presented here. Many issues regarding the conceptual model, the method of presenting data, the methods of summarising and identifying gaps in the data, and the influence of the latter on use of fertilizer in agro-ecosystems on a worldwide basis were discussed at the seminar, and the main conclusions are summarised in Chapter 7. The means by which man can manipulate nutrient cycles through the better use of fertilizers are then described (Frissel). Many other methods of manipulation which involve changes in crop, cropping system or animal grazing systems are possible b u t time did not permit a detailed investigation of these although their possible application is briefly described at the end of Chapter 3. The discussion concludes with a consideration of what data or researches are still needed to improve the precision and value of nutrient balance sheets of the type used here. The last chapter (8) summarises some of the major findings and indicates h o w accurately the unified data support the conclusions of the discussions. It concludes by listing the data that are still required to increase the precision of nutrient balances for agricultural eco-systems. The acquisition of more precise data may eventually enable agronomists to move towards more accurate forecasting of the effects of changes in fertilizer practice on both agricultural production and on the quality of the environment on a worldwide basis.

Chapter 2 PRINCIPLES OF NUTRIENT CYCLING

Elements, compartments, pathways and transfers, time-scales, rates of transfer and nutrient balances (Newbould)

Nutrients which are essential for the growth of plants and animals are passed from soil -* plant -~ animal -~ soil again; this sequence of transfers through a series of compartments constitutes one of the simplest representations of a nutrient cycle. In most practical situations, whether concerned with natural or man-controlled systems, there are many more compartments and complex transfers involved in the cycling of nutrients than shown in this basic scheme. Many cycles are polycyclic in that an element may cycle through several processes within a compartment, e.g. soil, before being passed to the next compartment (plant). The length of time for a nutrient to complete a cycle varies from minutes in transfers involving micro-organisms, to months for uptake and growth by annual crop plants, to years for intake and growth of animals and to thousands and millions of years for transfers involving the physical environment, for example from atmosphere to land and sea and formation of rocks. Thus, the time scale of any nutrient cycle under study must be carefully defined and any measurement at an instant of time which is alone usually possible neglects some aspects of the dynamic nature of the cycling of mineral nutrients. To understand and quantify nutrient cycling of any element it is necessary to design a conceptual model to represent the main transfers and compartments. Many descriptive models with varying degrees of complexity have been described in recent reviews -- Cooke, 1967; Egunjobi, 1969; Halm et al., 1971; Till and May, 1973; Henzell and Ross, 1973; Wilkinson and Lowrey, 1973; Mort, 1974; Heady, 1975; and Svenson and SSderlund, 1976. An example of a very refined model (Van Veen, 1977) is described in Chapter 7. The scheme adopted duringthe present seminar and described in detail in Chapter 5 is similar to that described by Wilkinson and Lowrey (1973) with three main compartments or pools --- plant, animal (or livestock) and soil, the latter being divided into three sub-pools -- available, unavailable (soil minerals) and residues (soil organic matter). To quantify a nutrient cycle requires knowledge of the element under examination and its chemistry, of the nature and sizes of the compartments, the pathways between them, the quantity and rate of transfer of nutrients along them, the reference time period and definition of the area and boundaries of the system under consideration, e.g. pasture, farm, watershed, or agro-ecosystem (see Chapter 4).

ELEMENTS

The most important characteristics of elements which determine their cycling patterns are solubility in water, volatility and electrochemical potential or degree of chemical reactivity. Of the three elements studied at this symposium, nitrogen and its gaseous c o m p o u n d s are volatile and its solid compounds have high solubility in water so that nitrogen cycles are extremely dynamic and have many complicated pathways and transfers. Phosphorus compounds have low solubility in water so that only a very small proportion (1%) of the total phosphorus in soils and plants is present in the plant component (Hayman, 1975); thus, phosphorus cycles are generally less flamboyant than those with nitrogen. Potassium cycles are intermediate in complexity since potassium compounds are generally n o t volatile b u t have relatively high solubility in water. Potassium is more easily displaced from exchange sites in the soil than phosphorus and it is taken up by plants in higher amounts than phosphorus. THE PLANT COMPARTMENT

This includes all parts of the plant and it can be either the crop or that which is consumed b y livestock. In most intensively grazed or cropped systems nutrients spend only a small portion of the overall cycle time in the plant compartment. The same is n o t true for under-utilised indigenous vegetation or for forests where a portion of the nutrients may remain for long periods of time. In these cases it is often difficult to define the size of the pool. It is sometimes useful to split the plant pool into nutrients held in tops and in roots, as this is of assistance in dealing with harvested root crops and with the behaviour of roots left in the soil at the end of a growing season. THE LIVESTOCK COMPARTMENT

This consists of the nutrients held in animals consuming plant products. Retention of nutrients by the grazing animal is only a very small part of the amount consumed and most ingested nutrients are returned to the soil as excreta. Excreta become part of the soil pool the m o m e n t they reach the soil surface, b u t if they are collected from housed animals and stored they remain part of the livestock pool. Nutrients contained in living animals may increase as the latter mature and are only passed across the system boundary when livestock products are sold. T H E T O T A L SOIL C O M P A R T M E N T

(POOL)

This consists of nutrients in organic and mineral components, in the soil solution and on exchange sites; nutrients in the last two categories constitute the available soil pool. Plants are known to obtain their nutrients from the

available soil pool. Thus it is possible to consider one total soil pool or three constituent pools. It is important to consider the organic residue pool as a separate entity because of the very variable and often long residence time of nutrients in this form before becoming mineralized and transferred to the available pool. PATHWAYS AND NUTRIENT TRANSFERS In the process of nutrient cycling the three major nutrients pass between these pools along certain pathways. In theory, transfers between all pools in all directions are possible but in practice only certain of these transfers are of importance. Sometimes, e.g. mineralization and immobilization in soil, transfers in both directions occur simultaneously and it is usually only possible to measure the net result. In addition, nutrients may be transferred into and out of these pools directly by use of fertilizers or sale of agricultural products. Quantification of these transfers requires a definition of the boundaries of the system to which the nutrient cycle applies. It is also necessary to define the time period over which transfer occurs. TIME SCALES AND RATES OF TRANSFER The transfers between pools and along certain pathways consist of fixed amounts of individual plant nutrients. These can occur over short (e.g. second, minute) or long (e.g. year, decade) periods of time and may be expressed as high or low rates of transfer depending on the time scale chosen. For example, the rate per day at which a plant absorbs nitrogen from the available pool is much greater than the rate per day it is mineralized from plant residues, but because uptake often takes place over a short period in the year, whereas decomposition and mineralization of residues occur over a prolonged period, the a m o u n t per a n n u m may be equal. Indeed, in the absence of income and outflow from the system the average transfer per annum of a nutrient by these processes must be equal to maintain balance. It is impossible to choose a time base to suit the rates of all processes but it is necessary in studies of nutrient cycles to choose some arbitrary time base. Some confusion has arisen in understanding the significance of rates because of different techniques of measurement used in the hitherto separate disciplines which are now being brought together to construct nutrient cycles. For example, crop yields are traditionally measured in kg ha -~ y-~ whereas mineralization of nitrogen in laboratory studies is more usually measured as pg g-~ soil-' day -~ . The expression of all transfers as kg ha -~ y - ' obscures these inherent differences in rate.

NUTRIENT BALANCES

The state of balance of a nutrient in any pool can be deduced from knowledge of the net inflow and outflow of that nutrient. F o r any pool when inflow and outflow are equal there is a state of balance which is often referred to as equilibrium but should more correctly be called steady state. Steady state is defined as a state of no change in size of a pool where the sum of all inflows of a nutrient are equal to the sum of all outflows. Equilibrium, on the other hand, refers to a state of balance between transfers in opposite directions such as may take place between two pools. Thus, the plant pool may be in steady state when uptake of a nutrient from the soil is equal to its removal in the form of plant litter and product, whereas the relationship between immobilization and mineralization within the total soil pool may be described as an equilibrium if the amounts transferred by these opposing processes are equal. It is also possible to describe a state of balance for a whole system in which nutrients pass between several pools in a cyclic fashion. Where all transfers take place within the boundaries of this system it is described as a closed system. In an open system, on the other hand, nutrients may be transferred across the boundaries. Transfers of a nutrient into and out of the system may be in balance, in which case the system is in steady state for that nutrient. Alternatively, the transfers of that nutrient may be unequal, in which case the system may be said to be accumulating or declining in respect of that nutrient. Because nutrients behave differently the system may not necessarily be in the same state of balance for all nutrients. The principles described above were used to construct both a conceptual model and data tables (Chapters 5 and 6) appropriate to the information presented by the several authors.

Chapter 3 CONTROL OF NUTRIENT CYCLING The amounts of nutrients transferred between the pools of agro-ecosystems are influenced not only by conditions and processes within the system, but also by circumstances and controlling forces outside the system. In this chapter the relevance and importance of some of these controlling influences is considered. Kovda and La Riviere (1976) have stated that "the biological cycles of C, O, N, S and P constitute the life supporting system for our planet since their dynamics determine the composition of the atmosphere as well as the fertility of land and water". Although in this symposium it was not possible to discuss in detail the relationship between agro-ecosystems and the atmosphere, both climatic and atmospheric conditions exert a controlling influence on cycling processes. Furthermore, as Kovda and La Riviere (1976) point out . . . . . . . "Disturbances in these cycles may have global, regional and local implications which can only be assessed against the background of integrated interdisciplinary knowledge of the budgets and the flows of the cycle components and of the mechanisms mediating their conversion and transport". It is therefore necessary that consideration be given to those processes which mediate the mechanisms controlling conversion and transport of mineral nutrient elements. External control is exerted by the physical and chemical environment and is modified by the chemical nature of the element concerned, and its ability to respond to environmental influences. Internal control is exercised through the biological ability of the component parts of the system to respond to their biological, physical and chemical environment. Biological activities are necessary to complete the nutrient cycle of uptake--growth-- consumption-decomposition--release: all these biological activities are subject to their own controlling influences, detailed discussion of which is beyond the scope of this review. Agro-ecosystems, which are frequently characterised by the input of fertilizer and the output of food or fibre products, are especially subject to influence by man and his cultural operations. 3.1. EXTERNAL CONTROLS (Floate) Probably the most important external control of agro-ecosystems is exercised by energy, both through its regulation of photosynthesis and through the climatic effects of temperature on growth rate and upon the. temperaturedependent chemical and microbial processes in soils and plants. Although of great importance, further discussion of this aspect is beyond the scope of this symposium. Climate controls not only the supply of moisture to the soil but also regulates its rate of loss by evaporation and transpiration: it also governs the

seasonality of water supply which is all important for agricultural production during the growing season. Water is important as a transport medium, and because of the interactions between nutrient solubility and water supply which control nutrient availability for both plants and micro-organisms. Because of the importance of water in so many aspects of nutrient cycling the following section is devoted to a detailed consideration of transport in the water phase.

3.1.1. Transport in the water phase (Wartena) Two external features are responsible for the greater part of the water movements through the systems, namely precipitation and evaporation. This means that the weather causes a strong coupling between internal and external controls. Drainage is a third connection between the internal and external processes. Drainage is often influenced by human activities. The amount of precipitation cannot be influenced, b u t the transport velocities and pathways of the water in the ecosystem can. Evaporation and drainage can be influenced to a greater degree. The ways in which the influence can be realised are of different natures. When drainage can be modified, the total a m o u n t of drainage water does not alter in general b u t the flow velocities, the water content of the soil, the groundwater table and the pathways of water are changed considerably. Evaporation can sometimes be modified by the plant, depending on the availability of water. This is an example of an interaction between the two external factors, drainage and evaporation, via the ecosystem. Now evaporation is strongly determined by the available energy, b u t a change in the evaporation means a change of the energy flux densities on the boundary between the ecosystem and the atmosphere. This also depends on other features which are important for the ecosystem, such as the temperature. Water movement is a part of the water cycle which interacts with the availabie energy, and other meteorological factors such as wind velocity, stability, air humidity and air temperature. For a study of nutrient cycling the water movement is of more direct importance than the other factors and therefore most attention will be paid to the hydraulic cycle (Alissow et al., 1956; Domenico, 1972). A remarkable aspect of the hydraulic cycle is that continents have a positive water balance and consequently oceans have a negative water balance. Part of the precipitation on the land flows via the soil surface or via the subsoil to the oceans. From an agricultural point of view, other criteria are used. In the summer or in a dry period, the evaporation tends to be higher and sometimes much higher than the a m o u n t of available soil water plus precipitation (De Vries and Afgan, 1975); this means a water shortage during the summer. Irrespective of the surplus amounts in the wet period or in the winter, agriculturists will consider such a condition as one of water deficit. Fig.1 shows the part of the hydraulic cycle which is important for the availability of

1®

1®

?

f, 4,t l®

....

1®

1®

,£

..... ' U

Fig. 1. Pathways in a part of the hydraulic cycle.

nutrients (Dooge, 1967). The meaning of the different numbers is: 1, Precipitation; 2, Part of the precipitation which is intercepted by vegetation; 3, Ponding; 4, Surface run-off; 5, Water penetrating into the soil; 6, Water stored in the r o o t zone; 7, Water taken up by the roots; 8, Water leaving the root zone or water entering the root zone (by capillary rise); 9, Water in the unsaturated zone below the r o o t zone; 10, Water migrating directly through the unsaturated zone near surface water; 11, Water transfer via the saturated zone to surface water; 12, Exchange of groundwater and nearby surface water; 13, Long distance migration of groundwater to surface water; 14, Evaporation; 15, Dew; 16, Transpiration; 17, Groundwater from elsewhere; 18, Migration of surface water. The migration of a certain quantity of precipitation may proceed along various pathways e.g. 1, 5, 6, 8, 9, 11, 12, 13, the latter t w o sometimes covering many kilometers. The pathway composed of 1, 5, 6 and 7 is almost a shortcut and only a few dm long. A general statement on the time that water remains in the soil (residence time) is therefore difficult to make. Mathematical simulation models can be a great help in evaluating the processes, although these models will be rather rough. A fact which is n o t always realized, is that travel times may be remarkably long (De Vries and Afgan, 1975). Consider a situation in which an annual rainfall of 25 cm must be transported to a creek via p a t h w a y 12 over a distance of 300 m. If a water-filled pore volume of 33% is assumed, it appears that the mean water velocity equals 25/0.3 = 75 cm per

10 year. The residence time in pathway 12 of this water is thus 300/0.75 = 400 years. Many such situations exist and many statements a b o u t the present-day contamination not influencing our surface water or (deep) drinking water may therefore be misleading. The contaminant may still be underway. This situation is still more pronounced if the contaminant is partially (reversibly) absorbed. If it is assumed that only 10% of the contaminant, whether or not it be a nutrient, remains in solution, this does not mean that only 10% will pass the soil layer. The total a m o u n t will pass the soil layer, only its velocity will be reduced by a factor of 10 (10% being in solution and 90% being absorbed reduces the mean velocity roughly to 1/10}. Another complication is the presence of so-called stagnant water or dead water in soil. There is no contact between such a stagnant phase and a moving phase (De Vries and Afgan, 1975). At higher moisture contents, this phenomenon is probably less important. At low moisture contents its effect is important, b u t it is reduced due to exchange of moisture via the gas phase. Minerals resulting from weathering or from irrigation water concentrated by evaporation are, however, locked up in the stagnant phase. They can only reach the moving-water phase if the water content in the soil becomes so high that the stagnant phase disappears. Of course they can never be exchanged via the gas phase. Residence times of water are extremely important for transport and weathering phenomena. In order to estimate these times, detailed insight into the water movement is needed. At any given pF~ pores above a certain diameter are filled with air, whilst narrower ones are filled with water. Upon arrival of precipitation which has to be discharged, a fraction of the wide air-filled pores is temporarily filled with water; temporarily because the water will infiltrate into lower layers and air will enter again behind it. The residence time in these wide pores is n o t more than some hours, even during showers with a total precipitation amount of 20--50 mm. Meanwhile, the water in the narrow pores is displaced just some centimeters or only millimeters. This water remains stagnant until discharge of a subsequent rainfall. Thus, in the unsaturated zone, wide pores with residence times of a couple of hours (intermittently filled with air and water) border on narrow, waterfilled pores with intermittent flow and residence times of years. It should be noted that these residence times, which are so important for the ion transport and for weathering phenomena have, up to now, hardly been a subject of hydrological research (Sinnaeve, 1975). Therefore, only very rough estimates can be made on the basis of non-verified models. Two important things are clear from the descriptions given above. First: residence times in different reservoirs differ b y several orders of magnitude. Second: residence times are much more dependent on the behaviour of hydrological systems than on soil types (Domenico, 1972; Dooge, 1967). Of course, for residence times in the unsaturated zone, the soil t y p e is of importance, b u t quantitative estimates are not available for these cases.

11 TABLE 1 Residence times of water in the saturated zone of the soil Discharge

System

per year

and pathways

(mm)

Estimated residence time depending on the place of infiltration and on porosity

Watershed

of the soil or rock A. 250 mm

About constant

100--5000 years

slow discharge 17

350 mm 160 mm

partly 12

slow discharge 12 fast discharge 10

1--500 years 1 day--10 years

Merkenfritzbach (Federal Republic of

Germany, Land Hessen, Main area) 1600 ha

partly 12 B. 150 mm 100 mm 50 mm

(12, 17) (12)

(4, 10)

10~1000 years 1 day--10 years 1 hour--1 day

Okkenbroek (The Netherlands, IJssel area) 443 ha

As an e x a m p l e , t h e residence times o f d i f f e r e n t p a t h w a y s f o r t w o watersheds are given in Table 1. T h e first is a w a t e r s h e d o f 1 6 0 0 h a in low m o u n t a i n s o f T e r t i a r y volcanic origin with a h e i g h t b e t w e e n 270 m and 500 m + MSL (Mean Sea Level). T h e s e c o n d w a t e r s h e d is p a r t o f a fiat area o f Pleistocene s a n d y subsoils with a c o v e r o f sand d e p o s i t e d d u r i n g the last ice-age b y the wind, with local p e a t f o r m a t i o n . T h e area o f this w a t e r s h e d is a p p r o x i m a t e l y 4 4 3 ha.

Transport of dissolved compounds. Water which moves d o w n w a r d (5--8) carries n u t r i e n t s f r o m t h e topsoil vertically first into and n e x t o u t o f t h e r o o t zone. P a r t l y this is a fast t r a n s p o r t , b u t in t h e n a r r o w pores t r a n s p o r t is very slow. Up t o n o w t h e r e are h a r d l y a n y m e t h o d s o f measuring this vertical nutrient transport. One o f the difficulties is t h a t t h e b e h a v i o u r o f the u n s a t u r a t e d vertical flow is greatly d e t e r m i n e d b y the reactions o f the g r o u n d w a t e r table. As a cons e q u e n c e p e r c o l a t i o n m e a s u r e m e n t s o n soil c o l u m n s o f a smaller h e i g h t t h a n the distance b e t w e e n the surface and t h e g r o u n d w a t e r table give rise t o errors which can cause a d i f f e r e n t o r d e r o f m a g n i t u d e in l a b o r a t o r y e x p e r i m e n t s t h a n o c c u r s in nature. T h e v e l o c i t y o f the vertical t r a n s p o r t decreases fast n e a r the g r o u n d w a t e r table. In several climates t h e n u t r i e n t s carried stagnate in a z o n e just a b o v e and b e l o w t h e g r o u n d w a t e r table, f r o m w h e r e t h e y rise up t o t h e r o o t z o n e in d r y periods during the growing season. In this case leaching is n o t a final loss. T h e a m o u n t s can vary with t h e actual w e a t h e r c o n d i t i o n s f r o m y e a r t o year. Interception. Substances f r o m the a t m o s p h e r e m a y be i n t e r c e p t e d in a solid, a dissolved, or a gaseous state b y the leaf c a n o p y o f t h e vegetation. Subs e q u e n t l y , t h e y m a y be washed d o w n b y rain, t o g e t h e r with s o m e material

12

lost by the leaf tissues themselves. Precipitation contains minerals, but only on bare soil does all the precipitation reach the soil surface immediately. On vegetation, most of the rain wets the leaves and then drops onto the soil. A part is intercepted by the vegetation and evaporates afterwards. The minerals are deposited on the leaves. With the next rain those minerals reach the soil. Meanwhile, dry deposition has also taken place on the leaves. This is sometimes called filter action, which is misleading. Such deposits are also washed down. Now, in a forest one is n o t able to investigate the composition of rainwater independently from the trunk discharge. The minerals reaching the soil are the minerals which are in the precipitation, together with the dry deposited material. On low vegetation (arable land, pastures) only the precipitation can be measured. The a m o u n t of dry deposits cannot be measured. This does n o t mean that the a m o u n t of dry deposition on low vegetation is negligible, nor that it must be lower than on a forest. Several reasons can be advanced that the dry deposit on short vegetation will be lower or higher than on a forest, but it will be of the same order of magnitude. For short vegetation one has to keep dry deposition in mind, but even a qualitative estimation of it will often be a gamble.

Run-off. Another transport mechanism involving water is the run-off. Water running over the surface of the field transports material and sometimes also deposits it. In other cases the transported material flows into ditches and rivers. This means t h a t run-off often causes a redistribution of soil material, leaching of superficial layers, infiltration of minerals on other sites and removal outside the ecosystem. Hydrological run-off studies are mostly directed to the amounts of discharged water. For nutrient transport, the composition is also of interest, but even more so is the origin of the material. The soil types, vegetation, stage of development, etc. have a radical influence on the processes of material transport. This is a very complex but important field of research. 3.2. INTERNAL CONTROLS (Floate) The external factors of energy and water supply also have important effects upon nutrient cycling through their influence upon biological processes operating in all the compartments of agro-ecosystems. In this section the importance of these biological and biochemical processes in controlling the transfers of mineral nutrients between compartments of the system is discussed. It would be impossible to describe all such processes in detail because for example, the operation of the controls in the soil c o m p a r t m e n t would involve a detailed analysis of all the processes of uptake, exchange and transfer known to soil science. Similarly a description of the processes in the plant and animal compartments would involve the detailed consideration of plant and animal physiology. Such considerations would n o t only be too detailed for the present

13 purpose b u t would necessarily involve many more sub-compartments and transfers along a number of food chains. Extreme simplification of many parts of these systems (which is necessary at the ecosystem level of analysis) might obscure many important subsidiary stages which may be critical rate-determining steps. The operation of internal controls may be illustrated b y considering some of the processes which bring about change in the a m o u n t of nutrients in the available soil nutrient pool. The supplies to this pool (which are described in detail in Chapter 5 and quantified in Chapter 6) would include nutrients conrained in manure, waste, litter, fertilizer, irrigation and flood water, the excreta of grazing animals and in the breakdown products of soil organic and mineral materials. The amounts of nutrients in these materials, and from these varied sources, depend u p o n a large number of factors and processes which include: the kind and class of livestock and their grazing behaviour; the kind, composition and physical form of fertilizer; the mineral and contaminant content of water; the kinds and numbers of micro-organisms taking part in breakdown processes; and the conditions of aeration, acidity, and temperature which determine their activity. Similarly, the removals from the available soil nutrient pool would include the nutrients lost b y volatilization and leaching, uptake by the crop, and fixation by other soil constituents. The amounts of nutrients so removed would also be controlled b y a large number of factors and processes which might include: soil moisture and organic matter content, acidity, aeration, temperature; pattern and seasonality of rainfall; permeability of the sub-soil; kind and stage of growth of crop plants; the presence or absence of mycorrhiza and other organisms; and cultural operations to the crop. It is thus evident that the state of balance of available nutrients in the soil is subject to a very large number of controlling influences -- some biological, some environmental, and some controlled b y man. It is also evident that similar considerations apply to the processes which control the amounts of nutrients transferred between other pools in the system. Furthermore, the balance is in a very dynamic state, and an annual balance of supplies and removals does n o t fully describe its changing status. In fact there is great variation in the rates at which some of these processes operate from, for example, the rapid dissolution of some forms of fertilizer to the very slow decomposition of residual soil organic matter. Dynamic aspects of agro-ecosystems will be considered more fully in a later chapter. From this discussion of system controls it may be concluded that man can have very far reaching effects on nutrient cycling in agro-ecosystems which, in turn may affect their stability. This influence is exerted primarily through management of soil, choice of crops and fertilizers, and the application of cultural practices. Because of the importance of biomass for the (temporary) storage of nutrients, the following section is devoted to the retention of nutrients b y the biomass. Section 3.3 illustrates some of the changes which the domestication of livestock and long continued arable cropping have produced in the past.

14

3. 2.1. Retention o f nutrients by biomass (Vervelde) Leaching of nutrients can be considerably retarded by retention of nutrients in the plant and animal biomass, or even be temporarily reversed by plants lifting nutrients from the deeper layers to the surface. Both the aerial and the subsurface biomass are very efficient in recovering and concentrating essential nutrients and protecting them from being carried away. The biomass tends to achieve a certain mineral composition. It is true that for plant biomass, the mineral composition is affected by the mineral status of the growth medium, but it may still be considered characteristic for a species or for a t y p e of vegetation. For vegetation in general, one might take the contents in the dry matter as a rough guideline. Note also that inactive biomass, such as wood, senescent or even dead materials, has to be included in varying proportions in the biomass weight. This explains part of the specific differences in mineral composition observed. Once stored in biomass, the nutrients are subject to very small losses due to direct leaching through the epidermis or the skin by rainwater or due to loss of b o d y fluids. By far the greater part is n o t liberated before the time the biomass is decomposed after death or consumed. Decomposition and consumption use up all biomass. The ratio of these destinations depends upon the number of consumers present in relation to the rate of primary production. Non-consumed biomass will eventually die and be decomposed. Both decomposition and consumption may lead to secondary production of biomass. The conversion rate varies. The efficiencies are between 0 and 25% roughly. They increase with the rate of growth and the rate of production (e.g. of milk and eggs) of a decomposer or a consumer. At low growth and production rates most of the food or substrate is used for maintenance, so that the conversion rate will be low. In agriculture, the conversion efficiency of the biomass eaten by the animals will seldom be below 5%. Since n o t all vegetation is eaten, a low conversion efficiency of the eaten part would make economical utilization of the area unlikely. Yet, in primitive agriculture, with animals suffering from climatic and health hazards and from temporary f o o d or water shortage, a low food conversion efficiency~is prevalent. The part of the eaten material n o t converted into secondary biomass is used for respiration or excreted as faeces. The mineral nutrients contained in this part and excreted in the faeces, together with those of decomposing faeces and uneaten dead biomass are set free during the process of decomposition. If no parallel growth of new plant biomass takes place, as will be the case in cold seasons or after dry seasons when regrowth has only just started or again with over-grazing, the nutrients are subject to leaching, run-off, denitrification and volatilization as ammonia. Leaching will only lead to permanent losses if the nutrients are carried b e y o n d the r o o t zone of the new growth. Thus the losses depend upon the length of the period with depressed or stagnant growth, in fact upon the biomass fluctuation over time.

15 3.3. LONG-TERM EFFECTS OF AGRICULTURE (Frissel} There are indications that both crop production and domestication of animals in Europe started about 5000 years ago (Louwe Kooijmans, 1976) and that activities on a larger scale date back to about 2000--3000 years ago. In 480 B.C. the Spartan Leonidas defended the pass of Thermopylae against a Persian majority. He did this with only 1000 men, indicating that the passage was very narrow indeed. At present, a coastal plain more than 5 km in width extends over the site of the former pass. This coastal plain is formed by deposits of silt resulting from land erosion. Although we cannot conclude that in 480 B.C. this deposition of silt was absent, it was certainly still at a very early stage of development, indicating limited erosion and limited agricultural influence before 480 B.C. The existence of inland harbours such as those at Ravenna in Italy and at Swammerdam in The Netherlands (which was a Roman harbour) also indicate that the rate of silting in earlier times, both in northern and southern Europe, must have been less than that during the last two millenia. Apart from the fact t h a t both places are now situated far from the sea, it is almost certain t h a t no harbour would ever have been built there if as much silt was deposited in these areas as is at present. A detailed analysis and dating of clay deposits in the delta of the river Rhine also indicates an increased sheet erosion from loess soils (grey-brown, podsolic soils) for northwestern and Central Europe in the post-Roman period (H. de Bakker, personal communication, 1975). All this may indicate the disastrous results of shifting agriculture, or the results of cutting forests for timber and firewood or for clearing areas for agricultural purposes. As has been said, agricultural activity on a larger scale began rather late in Europe. At the time t h a t Leonidas defended his pass, a few civilisations had already collapsed in the valley of the Euphrates and Tigris as a result of improper irrigation techniques, followed by salinisation of the soil; the forests of the Lebanon had vanished as a result of intensive cutting, and in Africa the Sahara was formed, perhaps as a result of domestication of h o o f e d animals followed by over-grazing. South-east Asia shows regions where people have seen more pleasing effects of their activities; sawahs to produce rice have been in production for thousands of years, and many of them are still productive. Nevertheless, the sawahs have also considerably changed the natural environment. More recent major examples of sacrificed natural areas are f o u n d in The Netherlands where parts of the sea have been reclaimed, and in the central plains of North America where m a n y areas were treated so improperly, that after the bisons and prairies had disappeared, so did the soils on which the crops were to be produced, leaving behind soilless and vegetationless 'Badlands'. The cutting of firewood by the growing population of south-east Asia for cooking purposes, and the over-cutting of tropical forests for timber are two other processes which will change the future environment drastically.

16

3.4. MANIPULATION OF SYSTEM CONTROLS

(Floate)

Not all agro-ecosystems result in such drastic changes and it could be argued that past disasters occurred as a result of man's incomplete understanding of the processes he was influencing. By contrast, it is possible that with proper comprehension of nutrient cycling in agro-ecosystems, and of the effects of control measures, in the future man may be able to maintain and improve the agro-ecosystems upon which he relies for survival. Potential control points in the cycles of mineral nutrients in pasture ecosystems have been discussed by Wilkinson and Lowrey (1973}. They conclude that improvements may be brought about in three ways: {a) increasing the available soil nutrient pool, (b) increasing the transfer rate between constituent pools, and (c) decreasing the losses of nutrients from the cycling pool of nutrients. Potential management methods for controlling nutrient cycling in agro-ecosystems include the application of manures and fertilizers, soil management, the selection of crops and crop management systems, and the manipulation of animal management systems. Some of these aspects are considered further in Chapter 8.

17

Chapter 4 DESCRIPTION AND CLASSIFICATION OF AGRO-ECOSYSTEMS (Frissel) 4.1. I N T R O D U C T I O N

As indicated in Chapter 1, the agro-ecosystem, normally as represented by a single farm, was chosen as the unit for study because of its easily recognisable boundaries and the probability that relevant data on the movement of nutrients within it could be collected or, at least, estimated from published information. According to a proposal by G.J. Vervelde, an agro-ecosystem may be defined as a recognisable part of the biosphere, affected or determined to a certain degree by agricultural practices, and deriving its properties and features from those of its structural components and, most typically, from interactions between those components. In more simple words, an agro-ecosystem is an ecosystem which is used for agricultural purposes. The term agro-ecosystem includes, however, something contradictory, because it has become c o m m o n practice (see Tansley's definition (1935) already given in the introduction) to define an ecosystem as a closed biological system, i.e. an ecosystem can be thought to be separated from the surroundings by boundaries through which no transport of material occurs. The main characteristic of an agro-ecosystem is that it is a system which produces food or fibre which is passed through the boundaries of the system per se, and as such conflicts with the established definition of an ecosystem. Thus, it is an open system so far as transport of nutrients across the boundaries is concerned. In particular situations it may be useful to go to a higher order system level and thus make the definition of an agro-ecosystem wider. This is, for instance, the case if all agricultural products (and only those) are consumed by the local population and all wastes (plant, animal and human) are returned to the agricultural areas. A higher order system of this type is n o w a closed system as regards nutrients. In this publication such higher order levels will be called closed agricultural systems. It is worth noting that the systems of the latter type are open for energy and water, the t w o remaining prime determinants of crop and animal production. From an agricultural point of view the t w o most important criteria upon which to base a classification of the 65 agro-ecosystems described in this report are type of farming and the yield. The yield is considered to include all harvested products -- edible crops, non-edible parts and straw (if removed from the field), milk, meat and wood. The nitrogen o u t p u t was selected as a measure for the yield, and the agro-ecosystems described in this report are listed in order of increasing yield in Table 2, and are plotted against t y p e of

18

type of agricultural system .Hdl ext.meat production T

~ ext. arable farming

~j

~

"~

forestry ~ext. dair>

farrrling

~J' : l i v e s t o c k port : :

I

mixed (selfsustainmg) • •

•

farming arable

"

'

' int. m i x e d -

i

0

20

part

40

60

•"

•

farming

int. a r a b l e f ~ r m ing

horti~:ulture ~

•

....

80 1(]0 120 140 160 180 .... 4()Q nitrogen output of agricultural systems (kg/ha)

Fig. 2. Outputs of agricultural production systems, expressed as k g nitrogen per ha per year. The black dots represent agro-ecosystems described in this publication, the lines connect similar agro-ecosystems. Details of how this figure was prepared are described in Chapter 5.

agricultural production system in Fig.2. This grouping of systems shows that the o u t p u t of nitrogen increases with the sophistication and intensity of the system and that there is a larger range of variation in o u t p u t with the most intensive systems. Relationships of this t y p e are discussed in more detail later in this report and when the data on nutrient cycling have been presented. It is instructive to examine historical transition in agricultural production systems from simple food gathering to the most modern intensive horticultural and arable farming practices. 4.2. AGRICULTURAL PRODUCTION SYSTEMS

4. 2.1. Food gathering The oldest production system is the so-called food gathering system. People gathered their f o o d by harvesting native plants and animals, the system is a closed one and, as such, a long-lasting system. However, the productivity per ha is very low.

4. 2. 2. Extensive livestock farming The domestication of herbivorous animals in northwestern Europe started a b o u t 5000 years ago (Louwe Kooijmans, 1976). In the middle east it may be even older. Extensive livestock farming is still an important system at present. The advantage of the system is that the tedious work of searching for consumable plants is carried o u t b y animals. Besides that, the system offers a

19 possibility of converting crops (e.g. grasses) n o t suitable for human consumption into products which are consumable by man. Often the system is used in areas where crop production is impossible. Within this context it is of importance that most nitrogen-fixing plants can be consumed by livestock and n o t by man, and so it is possible to make an efficient use of the nitrogen-fixing plants in those areas. This advantage is, however, partly counterbalanced b y the nitrogen losses which occur by volatilization of ammonia from excrements. For potassium and phosphate the system is very efficient, most phosphates and potassium being returned to the soil without losses. Only the phosphate and potassium present in meat and milk are withdrawn from the system. As the non-edible parts of these products are low, the phosphate and potassium losses are also comparatively low. Often phosphate is the growth-limiting factor and in this case livestock must consume more dry matter than usual to obtain sufficient phosphate. In this contribution all livestock systems which do not apply fertilizers (or use only very small P and K dressings) and/or do not use supplemental feed are considered as extensive livestock systems. To them belong the meat or mainly meat-producing systems Husz-1, -2 and -3, Newbould + Floate-1, -2 and -3, Noy-Meir + Harpaz-1 and -4 and Williams-l, and furthermore the dairy farms Jacquard-1 and Henkens-1. (See Table 2.)

4. 2. 3. Shifting agriculture Shifting agriculture probably belongs to the oldest arable systems. It involves cutting and burning of the standing forest vegetation. Most minerals stay in the ash, b u t part of the nitrogen is lost during burning. Crops planted in the newly cleared soil do well, b u t in two to three years the mineral reservoir becomes depleted and production declines. At this time the plot is allowed to return to native vegetation and a new field has to be cleared. The productivity of this system is low, because of the high losses of nitrogen combined with soil erosion, and the system is a declining one. After repeated burnings the system is no longer able to produce w o o d y species, grasses take over and the "shifting management" becomes impossible. At present this system is still in use in large areas in South America and Africa and also, to a lesser degree, in south-east Asia. A nutrient balance of such a system is, unfortunately, missing.

4.2.4. Extensive arable farming To this system belongs the production of crops with or w i t h o u t very small amounts o f fertilizers or manure. For a part this system depends on the decomposition of the organic soil fraction which was formed before agriculture was practised. Some depletion of organic reserves may occur under agriculture but the significance of this depends upon the rate of replenishment. From the Dutch polders it is recorded that the natural fertility was drastically reduced within a b o u t 30 years of their reclamation. (The Dutch term " p o l d e r " relates

Refereoc0

Noy-Meir + Harpaz-1 Husz-2 Husz-1 Damen-1 Newbould + Floate-I Newbould + Floate-2 Newbould + Floate-4 Husz-3 Noy-Meir + Harpaz-4 Newbould + Floate-3 Williams Newbould + Floate-5 Newbould + Floate-6 Noy-Meir + Harpaz-2 Noy-Meir + Harpaz-3 Thomas + Gilliam-8 Husz-9 Thomas + Gilliam-7 Ulrich-2 Husz-6 Ulrich-3 Husz-10 Ulrich-1 Newbould + Floate-7 Damen-3

Systemdescriptio.

Wildlife on semi-arid Israelian pastures, no utilisation by man Shrub steppe (Monte), Argentina Steppe and semi-desert, Patagonia Dutch mixed livestock farm o f 1800, livestock part o f Damen-3 High elevation moorland, sheep, U.K. Traditional hill-sheep farming, U.K. Improved hill-sheep farming, hill grassland part of N. + FI-3 ~ High tableland mid-Andes, sheep, lamas, goats, 5% arable land Sheep on semi-arid Iaraelian pastures Improved hill-sheep farming, paddocks + hill grasslands, U.K. 2 Subterranean clover pastures, Australia2 Improved hill-sheep farming, paddock part o f N. + Fl.-3 ~ 2 Meathop Wood, U.K. Extensive grain, semi-asid area, Israel, grain harvested, straw returned Extensive grain, semi-asid area, Israel, grain + straw harvested Douglas fir (37 years), Washington Shrub and tree savannas, central Brazil, livestock part of Husz-7 LobloUy pine, Mississippi Coniferous forest on grey-brown podsolic soil, central Europe Shrub and tree savannas, central Brazil, livestock part o f Husz-4 Deciduous forest on grey-brown podsolic soil, central Europe Arid + mesophytic transition woods, S. America, all types of products Deciduous and coniferous forests, acid soils, northern hemisphere Intensive sheep farming, grass and clover, U.K. Dutch mixed livestock farm o f 1800 on clay, 50% arable land

Agro-ecnsystems described in this publication

TABLE 2

-~

11.6 12 12.9 13 14.8 15 17 18

11

0 0.4 0.6 1 I 1 1.3 1.9 2 3 5.8 8 9 10 10 10.3

~

i

x x x x x x x x

x x

i~

~

x x

~

~

x

x

x x

X

x

~

x

~

~

x

×

x

~

~

~

~

×

~

~

i

x

~

~

~

~

~

b~

Henkens-1 Kolek-2 Jacquard-1 Husz-4 Henkens-2 Newbould + Floate-8 Jacquard-2 Husz-11 T h o m a s + Gilliam-3 Jacquard-8 T h o m a s + Gilliam-6 Husz-13 Husz-5 Hnsz-7 Damen-2 Jacquard-4 Jacquard-3 Noy-Meir + Harpaz-5 Jacquard-5 Henkens-3 Newbould + Floate-9 T h o m a s + Giniam-5 T h o m a s + Gilliam-4 Jacquard-6 Noy-Meir + Harpaz-6 Yatazawa-4 Husz-12 T h o m a s + Gilliam-1 Yatazawa-2 T h o m a s + Gilliam-2 Yatazawa-I Kolek-1 Husz-8 Henkens-4 Henkens-5 Yatazawa-6 Yatazawa-3 Henkens-6 Yatazawa-5 Jacquard-7

19 19.3 20 20.6 24 26 30 34.1 36 36 38 39.7 43.9 45.7 49 60 63 66 70 72 77 79 80 80 81 82 84 85 88 90 96 99 113 115 126 137 162 166 175 400

' Arbitrarily derived from Newbould + Floate-3 for classification purposes by editor (assumed 3/~hill land, 1Apaddock). 2 Only small amounts of P-fertilizers (< 20 kg P h a - ' y-~), neglected for classification purposes.

•Dutch dairy farm, clay of 1937 Slovakian m o u n t a i n farm, mixed system, use of supplementary feed French dairy a n d / o r m e a t farm, grazing, no fertilizers Shrub and tree savannas, central Brazil, 25% arable land Dutch dairy f a r m of 1937 clay, use of supplementary feed Intensive sheep farming on grass only, U.K. French intensive mixed farm, 7595 of leys used for grazing Tropical and subtropical arable farming, small f a r m s y s t e m Wheat, central Kanzas French intensive arable farm, irrigated beans Grazed bluegrass, western North Carolina Arable farming, temperate zones S. America, mixed f a r m i n g Shrub and tree savannas, central Brazil,arable part of Husz-4 Shrub and tree savannas, central Brazil,5 0 % arable land Dutch mixed livestock farm o f 1800, arable part o f Damen-3 French intensivemixed farm, 5 0 % of leys used for grazing French intensive mixed farm, pure legumes, 50% used for grazing Intensive grain farming, semi-arid area, Israel, low utilisation French intensive mixed farm, 25% o f leys used for grazing Dutch dairy farm, clay soil, 1972, with fert. + supplem, feed Winter wheat, U.K. Cotton, California Irish potatoes, Maine French intensive mixed farm, without grazing Intensive grain farm, semi-arid area, Israel, high utilisation Citrus, apple, pear, peach, grape, persimon, Japan Tropical and sub-tropical arable farming, plantation system, S. Am. Corn for grain, northern Indiana Upland rice, wheat, barley, sweet potatoes, Japan Soy bean for grain, N.E. Arkansas Paddy rice,Japan Slovakian lowland farm, arable land, livestock w i t h o u t grazing Shrub and tree savannas, central Brazil, arable part of Husz-7 Dutch dairy farm, clay, use o f fertilizers and m u c h suppl, feed Dutch arable farm, crop rotation, beet tops ploughed in Tea plants, Japan Vegetables, mean o f ten leading types, Japan Dutch arable farm, clay, crop rotation, beet tops r e m o v e d Forage crop, grass--legume mixture, Japan French intensive grass production, without animals x

×

x

x

x

x

x

x

×

X

x

x

x

×

x

× x

x

x

x

x x

×

×

x X X

x

x x

x x ×

X

× × x

x

× ×

to b-a

22 to an area where the water table can be regulated and controlled independently of the water level in the surrounding area. ) The reclaimed Lake Kopais in Greece had lost its natural fertility within 15 years, probably as a result of the relatively high temperatures in this area. In Saskatchewan {Canada), where the temperature is considerably lower, soils which have already been in production for about 100 years have lost only about one third of the nitrogen stored in the soil organic matter. If these soils are left fallow every second year, mineralized nitrogen accumulates and the use of nitrogen fertilizers is not necessary. If we investigate the traditional agricultural areas, it appears that before the introduction of fertilizers, most of the extensive arable areas were already depleted so that they had to rely either upon N2-fixation, and dry-wet deposition, or the use of litter. Because pea and bean plants are almost the only ones which fix nitrogen and provide a crop suitable for human consumption, the systems usually remained nitrogen deficient. In particular cases crops such as lupins, Calapogonium, Centosema and Crotolaria are used as green manure. Sometimes the straw is returned to the soil, but especially if this is n o t the case, the losses are high and the productivity low. As a result, the system is not very common; after the depletion period the soils are abandoned, or use is also made of manure or fertilizers. The agro-ecosystems Noy-Meir + Harpaz-2 and -3 refer to a pure extensive arable area which has been in production for a long time. Forestry, considered as a type of extensive arable farming, is very common. Therefore, descriptions of nutrient balances of the forestry systems Newbould + Floate-6, Thomas + Gilliam-7 and -10 and Ulrich-I, -2 and -3 are included. 4. 2. 5. Mixed farming or self-sustaining unit system Typical examples of this system are the so-called "mixed livestock farms" as they developed in Europe, and the sawah-homegarden system which developed in south-east Asia. It was, and probably still is, the most important agricultural system on earth. It is practised on comparatively small plots supporting only one family or another usually small, social group. The cultivation techniques have been evolved and improved over a long period of time and are much more sophisticated than one might think. The problem is that only some of t h e crops are able to fix nitrogen. They are mainly leguminous crops such as beans, soybeans and lucerne. None of the important crops such as grass, wheat, rye, corn or potatoes fixes nitrogen; these crops depend greatly on the management technique for their nitrogen supply. The whole cultivation method is focussed on methods of supplying the non-fixing crops with nitrogen. For a major part, this occurs by h u m a n and animal consumption of the crops containing the nitrogen, and a careful return of the animal and human wastes to the soft. In this system it is essential that each farm contains an area on which the nitrogen-fixing crops are cultivated, while another area contains the other crops. In the mixed livestock farms of northwestern Europe it was mainly the

23 pastures with clover or lucerne which served as the nitrogen catchment area. The livestock consisted of cows, horses and sheep. On the very p o o r soils, on which only sheep were kept, it was not possible to maintain permanent pastures; the development of heather plants, which are n o t consumed by sheep, was t o o strong. From time to time the heather was burned, and because grasses have a faster regrowth rate than heather, this restored the grass vegetation. The sheep were kept in stalls overnight, which gave the farmer a chance to gather the excrements and to produce manure for the arable areas. (Note: At present some of the heather fields are no longer grazed and therefore birches and other trees or sometimes grasses take over.) In the p a d d y soil-homegarden system in south-east Asia the paddy soil serves as nitrogen catchment area. The nitrogen is fixed by the blue green algae present in the water on the p a d d y soil or b y the floating azolla plants. When the soil dries up, the plant litter stays behind on the soil surface and decomposes: the nitrogen thus liberated is taken up by the rice. As usual in selfsustaining systems, the animal and human wastes are carefully collected, and are partly returned to the paddy soils and partly serve as manure for the homegarden. In the self-sustaining system the other important nutrient elements, phosphate and potassium, are almost completely recycled within the system; there is no external supply and there are no losses. The amount of phosphate and, to a lesser degree, also the a m o u n t of potassium determines the ratio between the nitrogen catchment area and the arable area. This ratio, which is almost a constant for a certain region, varies between 1 and 20. It also explains why such systems are almost always phosphate deficient. The ratio, nitrogen catchment area/arable area, is adjusted so that nitrogen no longer limits the production. But n o w the system is phosphate deficient. If, because of certain management techniques, it is difficult to keep the nutrient distribution between the livestock part and arable part in balance, sometimes alternation of livestock and arable areas is used to compensate for the unequal distribution of nutrients. This publication provides nutrient balances for three mixed (self-sustaining) farming systems which are referred to, respectively, as Husz-4 and -10 and Damen-3. The data represent mean values of arable systems and livestock systems; the separate nutrient balances of the arable systems and livestock systems are, however, also included. The reference numbers for the livestock areas are: Husz-6 and -8 and Damen-1, and for the arable areas Husz-9 and -13 and Damen-2. 4. 2. 6. Intensive agriculture

This system is mainly used in Europe, North America, parts of the U.S.S.R., Japan and on some other, smaller, areas. Its main characteristic is that it is an open system with a very high production. This production is maintained by a continuous supply of fertilizers allowing a steady export of crop products.

24 Waste and manure from an external origin are only applied if this is more economical than the application of fertilizers; this occurs only seldom. The high turnover rate of nitrogen, of course, also causes higher releases to the environment, b u t this does n o t necessarily mean that the release of nitrogen per unit crop p r o d u c t is high. The fixation of nitrogen is often completely suppressed as a result of the high nitrogen dressings. Potassium usually poses no problem, b u t phosphate does. It appears very difficult to increase the phosphate available for the plant r o o t in the same way as is done for nitrogen and potassium. This is because of the strong adsorption of phosphate. On soils with a small a m o u n t of available phosphate much more phosphate fertilizer is usually required than the plant takes. It is a reassuring fact that the strong adsorption prevents the leaching of these high quantities of phosphate. As for extensive farming systems, a separation can be made into: livestock farms (mainly meat production), livestock farms (mainly milk production), mixed farming systems, and arable farming. Besides that, "horticulture" can be added as a system type. Due to the fact that the systems do n o t depend on the efficiency with which biologically fixed nitrogen is used, the effects of nitrogen fixation on the output, if any, are much less pronounced. However, the outp u t range, mainly depending on the fertilizer dressing, varies extremely. The most remarkable systems are probably the dairy farms which use high imports of supplemental feed for cattle. Sometimes these inputs in the system are so high that phosphate and potassium fertilizers do n o t have to be applied at all. Although the outputs of potassium and phosphate belong to the highest in the world, the manure contains more than enough of these nutrients. In this publication the following agro-ecosystems are described: livestock meat system, Newbould + Floate-7 and -8; dairy farms, Henkens-2 -3 and -4; meat and milk oriented, Jacquard -2 to -6; mixed farms, Husz-5 and -13 and Kolek-1 and -2; arable farms, Henkens-5 and -6, H u s z - l l and -12, Newbould and Floate-9, Noy-Meir + Harpaz-5 and -6, Thomas and Gilliam-1, -2, -3, -4, -8 and -9, Yatazawa-1, -2 and -5, Jacquard-7; horticulture, Yatazawa-3, -4 and -6, Jacquard-8.

4.2. 7. Systems based on organized large-scale recycling structures The high fertilizer dressings, the losses of nutrients to the environment and the need for pesticides and herbicides in intensive agriculture have led to investigations of systems which are less intensified, b u t produce nevertheless a good yield. Some of the supporters of these alternative systems returned to the old mixed livestock system. Others rely on the decomposition of organic matter which was built up during the foregoing years in which fertilizers were used, or they just import manure from elsewhere. For highly developed areas, such as Europe or the U.S.A. and Canada there is, of course, no way to return to the self-sustaining unit system. With a dispersed agriculture and large urban centres, the direct return of wastes of the society is logistically complicated and, because of the dilute form of wastes

25 in domestic sewage, almost impossible. Nevertheless, it might be possible by composting the organic part of solid wastes or by converting them into methane, to develop a fertilizer recycling system, which reduces the mineral nutrient losses. Water purification plants can be installed which retain both nitrates and phosphates. Economic reasons have prohibited such a policy thus far. Social problems also exist. It will, for instance, be difficult to organise society in such a way that all types of waste, such as glassware, metals, plastics, compostable material, are kept separated. Yet such a separation is essential for economical large-scale composting or conversion of domestic waste to methane. 4. 2. 8. R e m a r k s

Tropical rainforests were not discussed, so as to limit the number of topics at the symposium. As far as they are used for regular wood production they can be easily included as a "forestry system". Furthermore, irrigated areas were n o t discussed as a separate system: such areas were classified in the same way as non-irrigated areas with similar characteristics.

27

Chapter 5 METHOD OF DATA P R E S E N T A T I O N (Frissel) A standard format for data presentation was necessary so that comparisons could be made between systems, and so that some grouping of like features could be made and that some summary and discussion of the data might be possible. The format in which authors originally submitted their data was, however, different from that finally agreed as a result of discussion during the symposium (Annex 1). It is important for the proper interpretation of what follows to understand which definitions have remained unchanged and which were modified during the symposium. In the original format the soil pool was presented as a single pool. The idea was that most systems are in a more or less steady state position with few changes in the residue pool. During the symposium it was decided to split the soil pool up, in order to be able to handle varying residue pools. The general definition of an agricultural ecosystem was given in Chapter 4 and it remained fundamental, b u t the classification of these systems was modified (Annex 1). The significance of this is that some authors described systems which were typical of the climatic regions defined in the original classification b u t which may n o t be typical of the range of agricultural production systems and yield which forms the basis of the agreed classification. To quantify nutrient cycling within an ecosystem it is necessary to define the boundaries of that system, and in the case of agricultural production systems it is also necessary to know the amounts of nutrients crossing those boundaries in the form of, for example, feed, fertilizer and product. In this presentation the boundaries are usally those of an individual farm b u t any differences are described by the authors. It was agreed that the agro-ecosystem boundaries should usually contain plants, soils and animals b u t exclude the human population; thus all nutrients in crop or animal products are defined as o u t p u t from the system. Exceptions to this or any other general assumptions are described b y the authors for individual systems. The model finally agreed for nutrient cycling in agro-ecosystems is illustrated in Fig.3. It consists of three main compartments (pools) - plant, livestock and soil, of which the latter is subdivided into available, organic and mineral pools according to the principles discussed in Chapter 2. The three major plant nutrients -- nitrogen, phosphorus and potassium, are transferred between these pools by processes which are controlled as described in Chapter 3, along certain pathways which are also illustrated in Fig.3. These pathways are indicated by reference numbers which refer to the particular transfers listed in Table 3, b u t in amounts and at rates which differ by several orders of magnitude. Because of this wide range, certain compromises had to be made and it was agreed to retain the originally proposed unit (kg h a - ' y-l).

28

Nitrogen and potassium are generally recorded to the nearest 1.0 and phosphorus to the nearest 0.1 kg ha-'. The general model, which is applicable to arable, livestock and mixed farming and to forest ecosystems includes both transfers of nutrients within the system and transfers across the system boundaries. Such transfers across the boundaries consist of inputs (as feed or fertilizer for example) and outputs (as crop products or volatile and other losses). Thus three types of transfer can be identified and these are indicated by symbols in Table 3. Input into the agro-ecosystem : indicated -~ X) Output from the agro-ecosystem : indicated (Y -~ Transfer between pools within the system : indicated (X -~ Y) where X and Y refer to the appropriate nutrient pools. The data, for each agro-ecosystem which follows in Chapter 6, are arranged in t w o tables for each system -- the first summarises the data for each of the uptake from atmosphere s e e a ~ consumption harvested crops

ammonia from manu re / ~ ~

feed indoors

.

grazing

-/

products remaining on field

Ing

uptake from soil

litter J

volatilization

~ ~ denitrificatio_~n~dust~

dry and

.~

.

material. immobdizotion~ "

runoff

Fig.3. F l o w

leaching

wet

~dep°siti°n , tion ~ M-~mineraliza

wea

j

soil mil

pool C

available soil nutrients, pool

A

chart of the nutrient transfers for an agro-ecosystem.

N-fixation

fertilizers

29 plant, animal and total soil pools while the second gives the details for available, organic and mineral nutrient pools within the soil. Some authors have contributed data for the total soil pool only. In both sets of tables the transfers are groupedas supplies (inputs) and removals (outputs) for each pool, and are identified by the reference numbers shown in Fig.3 and Table 3. The groups of data for each pool are headed "changes in a m o u n t " and the state of balance for that pool is assessed by equating supplies and removals. In some cases a steady state has been assumed b u t in other cases calculations of gains and losses have been made. Most authors have assumed steady state for plant and livestock pools and have calculated changes in the soil pools. Assumptions are indicated by symbols in the tables, and are described by the authors in the notes which accompany their data. It should be noted that in this m e t h o d of accounting, transfers across system boundaries are listed once only for the relevant pool, while transfers between pools within the system are accounted as removal from one pool and supply to another. It should also be noted that some transfers may be split into two parts which may next appear in one or t w o pools. For example, nutrient uptake from soil (30) may be split into uptake by roots (30r) and uptake by tops (30t) and these are both accounted as supplies to the plant pool: transfer b y droppings on grazed areas (9) may be split into organic (9b) and inorganic (9a) parts which are respectively accounted as supplies in the organic and available soil nutrient pools. Difficulties arise with the definition of certain transfers, and the footnotes to Table 3 explain some of these problems. Losses of nitrogen in volatile form may occur from animal excreta and when such losses can be identified with manure in the case of housed animals they are recorded as losses from the livestock pool: when the losses take place from excreta which have been deposited on the soil (as in a grazed pasture) they are accounted as losses from the soil pool. Further difficulties can arise with the measurement and accounting of certain transfers which take place simultaneously b u t in opposite directions. For example, the exchange of nutrients between available and organic soil pools by mineralization and immobilisation can usually only be measured as a net result. In this case it is the net transfer which is recorded as supply or removal in the appropriate pools. Where the net transfer is zero this is equilibrium as defined in Chapter 2 and should be seen to be in contrast to a net change of zero in any nutrient pool when that pool is said to be in steady state. The data contributed by individual authors for some 65 agro-ecosystems are contained in Chapter 6, and are arranged in 11 sections. Each system is referred to by author name(s) and sequence number, and the data are presented in tables numbered sequentially in the text. Thus the first system described b y Newbould and Floate is referred to as Newbould and Floate-1, and the corresponding data are given in Table 4. Each section also contains brief description(s) of the agro-ecosystem(s) together with notes on assumptions made by authors in their calculations of data.

30

TABLE 3 Summary of fluxes Flux 1. 2. 3. 4. 5. 6.

7. 8. 9. 10. 11. 12. 13. 14. 15.

16. 17. 18. 19. 20.

21. 22. 23. 24. 25. 26. 27. 28.

Input by feed for livestock Input by litter used indoors Transfer by consumption of harvested crops Transfer by grazing of forage Output of animal products Output by losses from animal and/or manure in stables and/or feed lots (Thus from any component before it reaches the soil) (can be split into: 6d, from droppings and 6 m, from manure) Output by manure (manure carried off or sold) Transfer by application of manure and/or waste (can be split into 8a and 8b) Transfer by droppings on grazed areas (can be split into 9a and 9b) Input by application of manure (can be split into 10a and 10b) Input by application of fertilizer Input by nitrogen fixation Input by application of litter, sludge and waste (can be split into 13a and 13b) Input by irrigation, sub-surface irrigation or flooding Note: capillary rise is not included Input by dry and wet deposition (rain, dust, bird droppings) Note: Nutrients taken up directly by plants from rain or atmosphere are accounted for in item 31 Transfer by weathering of soil mineral fraction Transfer by mineralization of soil organic fraction Output of primary products Output by denitrification Output by volatilization of ammonia Note: includes volatilization from manure, droppings and fertilizers (Thus from any material on or underneath the soil surface) Output by leaching Note: net effect (leaching minus capillary rise) Output of available nutrients by run-off Note: ' Surface leaching' included Output by dust Transfer by fixation in soil mineral fraction Transfer by immobilization in soil organic fraction Transfer by plant products (including litter) remaining on the field (can be split into 26a and 26b) Transfer by seed for sowing Output by run-off of organic matter

Symbols* -~ -* (P ~ (P -~ (L -~

L) L) L) L)

(L (L (L ~ A), (L ~ B) (L -~ A), (L ~ B) -* A), -* A) ~ A)

~ B)

~ A), ~ A)

~ B)

~ A)

(C ~ A) (B -* A) (P (A

(A (A (A -* (A-~ ( A ~ C) ( A ~ B) ( P ~ A , P -*B) (P ~ A) (B -*

31

TABLE 3 (continued)

Flux 29. Input by seed or seedlings

30. Transfer by uptake of nutrients by the plant (can be split into 30t, top and 30r, root) 31. Input by nutrients taken up directly from atmosphere by plants

Symbols* -, P) (A-* P) -~ p)

*Symbols indicate type of transfer, direction of flow and pool(s) involved.

3. W h e n a mixed farm system is considered as o n e system, the output 18 from the arable sub-system is included in the consumption (3) in the livestock sub-system: similarly, output (18) from grassland is included in grazing (4) in the livestock sub-system. 6. Losses of volatile ammonia from animals or their excreta (manure) are recorded in transfer (6) which is considered as a loss from the livestock pool. 7. The physical removal of manure from the system is also a loss from the livestock pool (7). 16, 24. Weathering (16) and fixation (24) are nutrient transfers in opposite directions which may take place simultaneously. Usually it is only possible to measure and record the net effect, although fixation of P fertilizer may be recorded independently.

17, 25. Mineralization (17) and immobilization (25) are nutrient transfers in opposite directions which may take place simultaneously. Usually it is only possible to measure and record the net effect.

20. Loss of volatile ammonia from excreta, or manure after application to the soil surface, is recorded as a loss from the soil pool (20).

26. Plant products remaining on the field (26) may.include litter, straw, haulms, etc. : the component entering the available pool is the inorganic part, the remainder enters the soil organic pool where it may become mineralized.

30. Most authors do not have data to split (30) into (30t) (30r).

31. Direct uptake of plant nutrients from the atmosphere is recorded in (31), leaching of vegetation by rain which occurs in forests is not considered, but may be used to calculate net uptake (30).

32 T h e sources o f data, as well as their accuracy, d i f f e r b e t w e e n the various transfers and b e t w e e n authors. In s o m e cases these were e x p e r i m e n t a l l y m e a s u r e d values, in o t h e r cases t h e y were m o s t likely values derived f r o m t h e literature and in still o t h e r cases, values calculated using certain assumptions which the a u t h o r s have described. Because one o f t h e objectives o f the s y m p o s i u m was t o distinguish areas o f well d e f i n e d knowledge, and areas w h e r e f u r t h e r research and d a t a collection were required, some a t t e m p t has been m a d e t o indicate the reliability o f the d a t a in the tables. T h e following s y m b o l s have been used: -: d a t a n o t relevant (transfer does n o t apply) t : trace a m o u n t o n l y : p m : significant b u t u n k n o w n a m o u n t 0 : zero w h e n used f o r n u t r i e n t t r a n s f e r 0 : s t e a d y state w h e n used for state o f balance * : e x p e r i m e n t a l l y m e a s u r e d value + : m o s t likely value derived f r o m literature or f r o m assumptions given in n o t e s ( ) : closing e n t r y derived f r o m balance calculations. Where a u t h o r s have a t t e m p t e d generalizations f r o m t h e i r data, t h e app r o p r i a t e section c o n t a i n s the a u t h o r s ' o w n discussion. General discussion follows in C h a p t e r 7. Editor's co mmen t . It s h o u l d be u n d e r s t o o d t h a t this final f o r m o f d a t a present a t i o n differs f r o m t h e f o r m in which a u t h o r s were invited t o p r e s e n t t h e i r data. A l t h o u g h all a u t h o r s were given the o p p o r t u n i t y t o u p d a t e t h e i r contributions, n o t all have d o n e so, and t h e r e m a y t h e r e f o r e be s o m e inconsistencies a m o n g t h e d a t a tables. In particular, n o t all a u t h o r s have indicated the reliability or source o f t h e i r d a t a or t h e y did n o t indicate w h e t h e r missing values are u n k n o w n , irrelevant or negligible: such missing values a p p e a r as dashes ( -- ) in the tables which f o l l o w in C h a p t e r 6.

33

Chapter 6

N U T R I E N T CYCLING DATA 6.1. INTRODUCTION The sections which follow are the original manuscripts from the authors. In some cases they have been shortened, transposed or adapted by the editor. A description is always included of h o w the data for the nutrient balances were derived, together with the information concerning the agro-ecosystem described. The editor has omitted descriptions of agro-ecosystems for which no data were provided, and has also omitted most sections which consider energy cycling because this was b e y o n d the scope of the symposium. The sequence of the system descriptions is more or less from west to east, and from north to south, starting at the 0-meridian. 6.2. AGRO-ECOSYSTEMS IN THE U.K. (P. Newbould and M.J.S. Floate) Seven different agro-ecosystems are described in this section, together with the two c o m p o n e n t sub-systems of one of these. These seven systems range from very extensive livestock farming through woodland to intensive arable farming and thus provide a few examples of the wide range of farming systems in the U.K. These systems were chosen to represent the classification originally proposed by the editor, b u t this classification was subsequently changed as described in Annex 1. These systems should, therefore, in no way be considered representative of U.K. agriculture because many important systems, e.g. dairy farming, beef production, and mixed cereal and livestock, have n o t been included. Under the heading of each system is given the classification assigned by the editor (Table 2) and some basic information on climate, elevation, location, soil, vegetation, size of unit, kind of livestock or product, and the agricultural objectives of the system described.

6.2.1. Extensive sheep production on high Pennine moorland Classification. Extensive livestock system. Reference: N e w b o u l d and Floate-1; High elevation moorland, sheep, U.K., Table 4. The U.K.-IBP (Tundra Biome) site at Moor House, England, is a nature reserve grazed by about 8500 sheep between April and September over an area of approximately 5000 hectares. The reserve (54°56'N, 2°45'W) is situated near Cross Fell in the northern Pennines, close to or above the tree line (550 m) and is representative of the marginal agricultural land in one of the most isolated parts of England. The climate is cool, w e t and windy, oceanic

34

TABLE 4 System type: Extensive livestock

Summary of n u t r i e n t flows (units: kg h a - '

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref. n o . N e w b o u l d a n d F l o a t e - 1

High elevation moorland, sheep, U.K.

Nutrient

N

y-1 )

P

K

C h a n g e s in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

REMOVALS:

29. 30t. 30r. 31.

Input by Transfer Transfer Input by

seeds or seedlings ............... by net uptake from soil ............ by net uptake from soil ........... uptake from atmosphere .......... TOTAL

-42* --

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by plant production remaining on field . T r a n s f e r b y seed f o r s o w i n g . . . . . . . . . . . . . . TOTAL

42

SUPPLIES-REMOVALS

--4+ -(38) -42 0

-3.6* ---

-11" --

3.6

11

-0.4 + (3.2) -3.6

--+ 1 -(10) -11

0

0

Changes in a m o u n t o f animal c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4. 5. 6. 7. 8. 9.

Input by Input by Transfer Transfer

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

. . .

Output by animal products ............... O u t p u t b y losses f r o m m a n u r e t o air, b e f o r e application ......................... Output by manure .................... Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s o n g r a z e d areas . . . . . . . TOTAL SUPPLIES-REMOVALS

----4+ 4 1' ---(3) 4 0

---0.4 + 0.4 0.1" ---(0.3) 0.4 0

----1+ 1 t* ---1) 1 0

C h a n g e s i n a m o u n t o f t o t a l soil c o m p o n e n t SUPPLIES:

REMOVALS:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . by seed for sowing .............. TOTAL

--+ 3 ---+ 9 ---+ 8 38 + 58

-0.3 + -----0.2 + 3.2 + -3.7

19. 20. 21. 22. 23. 28. 30.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off I . . T r a n s f e r b y net' u p t a k e f r o m s o i l b y p l a n t . . . . . TOTAL

t t 3+

---0.4 +

---9 +

15 + --42* 60

0.4 + --3.6* 4.4

2+ --11 + 22

SUPPLIES-REMOVALS See 22.

(-2)

(-0.7)

--+ 1 -----+ 2 10 + 13

(-9)

35

TABLE

4

(continued)

System type: Extensive livestock

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -1 y - l )

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no. Newbould and Floate-1

High elevation moorland, sheep, U.K.

Nutrient

N

Changes in amount SUPPLIES :

REMOVALS:

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer Transfer Transfer

by applicatiofi of manure and/or waste . by droppings on grazed areas ....... application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by weathering of soil mineral fraction.. b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n by plant production remaining on field . by seed for sowing .............. TOTAL

19. 20. 21. 22. 23. 24. 25. 30t. 30r.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... T r a n s f e r b y f i x a t i o n i n soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y i m m o b i l i z a t i o n i n soil o r g a n i c f r a c t i o n T r a n s f e r b y n e t u p t a k e ~b yv t ht h~e. i apnl ta n t .. .. .. .. .. .. .. .. .. Transfer by net uptake SUPPLIES-REMOVALS

SUPPLIES:

REMOVALS:

Transfer Transfer Input by Input by Transfer Transfer

by application and/or waste ........ by droppings on grazed areas ....... application of manure ............ application of litter, sludge and waste . by immobilization in soil organic fraction by plant products remaining on field . . TOTAL

17. 28.

Transfer by mineralization of soil organic fraction Output by organic matter, removed by run-off.. TOTAL SUPPLIES-REMOVAI.~

SUPPLY: REMOVAL:

24. 16.

2+ ---9 + -8 + -7? --

-26 t t

3+ --

t

t~ -----0.2 + pm pm --0.2

1+ ---2+ pm -10 + -13

--0.4 + 0.4 +

---9+ 2+

-Pro_,42 -45

t pm Pro6*3. -4.4

t pm

-19

-4.2

-

--

--

?1"

-22

9

o f soil o r g a n i c m a t t e r

8b. 9b. 10b. 13b. 25. 26b.

C h a n g e s in a m o u n t

K

of available soil nutrients

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

C h a n g e s in a m o u n t

P

1 +

---

P~8 + 39 7~ 1 5 ~" 22

0.3

-+

t

--pm 3.2 + 3.5

------

pm t --

t

---

+17

+3.5

--

---

pm pm

pm pm

--

--

--

o f soil m i n e r a l s T r a n s f e r b y f i x a t i o n i n soil m i n e r a l f r a c t i o n . . . . Transfer by weathering of soil fraction ....... SUPPLY-REMOVAL

36

in type and is sub-arctic rather than temperate. The growing season is about 180 days but the highest mean m o n t h l y temperature is only 10--12°C (Heal et al., 1975). The soils are mainly organic; blanket peat 0.5--5 m deep covers more than half the area and most of the remainder consists of peaty gleys and peaty podsols while brown calcareous soils with Agrosto-Festucum cover no more than 5% of the area. Blanket bog vegetation dominated by Calluna vulgaris, Eriophorum vaginatum and Sphagnum acutifolium occurs on peat while Juncetum squarrosi subalpinum and Nardetum subalpinum are characteristic of the peaty soils. The whole area is essentially c o m m o n grazing in the summer months for some 22 flocks of sheep which are wintered and produce their lambs on lower ground. NOTES TO TABLE 4. (Reference Newbould and Floate-1) 4. Intake by grazing sheep was on average 1 kg of dry matter sheep -1 day -1 (Heal and Perkins, unpublished data, 1975), which has been calculated as 930 kg ha -~ from AgrostoFestucetum, and 300 kg ha-' from blanket bog. However, it has been stated that consumption is less than 1% of production of the bog compared with up to 40% of the grasslands (Heal et al., 1975). Mean composition data used were Agrosto-Festuceturn 2.0% N, 0.15% P and 0.7% K and for blanket bog 1.2% N, 0.1% P, 0.3% K. Quantities are in the same order of magnitude as Barrow, Alaska IBP site (Bunnell et al., 1975). 5. Rawes and Welch (1969) give a mean live-weight increase of 14.9 kg ewe -~ which is equivalent to 23.8 kg ha -1, but sheep production, measured as net increases in weight of sheep over the season, for the whole Moor House reserve was given by Heal and Perkins (unpublished data, 1975) as 0.8 g m 2 y-l, or 3.8 g m= y-I from Festuca--Agrostis grassland. We have used 23.8 kg ha -~ y-~ and mean composition data of Sykes and Field (1972). 9. Droppings have been calculated on the assumption that animal retention of ingested nutrients is accounted for in removal of animal products. Hence total excreta returns equal consumption minus production. It is estimated that of the total nutrients ingested by sheep some 35% of N, 95% P and 15% K are excreted in faeces while the remainder appears in the urine. 12. Data quoted by Heal and Perkins (unpublished data, 1975) may be compared with amounts in the range 0.05--3.8 kg ha -~ for tundra in Finland (Kallio, 1975) and between 2 and 90 kg ha -~ for tundra mire in Sweden (Rosswall et al., 1975). 15. Data of Heal and Perkins (unpublished data, 1975) using data from Crisp (1966), Gore (1968) and Martin and Holding (1976). 17. IBP publications give data on rates of decomposition of organic materials (up to 25% per annum, but only 10% per annum for Calluna) but no data on the rate of release of mineral nutrients except that Rosswall et al. (1975) state that above-ground litter decomposition releases 2 kg ha -~ N per annum, and N mineralization of peat yields about 5 kg ha -~ per annum in the top 10 cm. 21. Sources as for 15, above. The overall system balance suggests a gain in N which is due to fixation and atmospheric inputs. If these estimates are wrong (e.g. N fixation may be 0.05--90) then the balance could be tipped either way. 22. Sources as for 15, above. 26. Calculated by differences between uptake (30) and consumption by grazing (4). All nutrients in plant litter assumed organic (Pool B) until released by mineralization. 30. Uptake of plant nutrients by vegetation has been calculated from production data of Rawes and Welch (1969) using 3600 kg ha -~ for blanket bog and 2000--2600 kg ha -~ for Agrosto-Festuceturn. The latter type covers no more than 5% of the area and for simplicity it has been assumed that the remaining 95% has a production similar to blanket bog.

37

6.2.2a. Traditional hill sheep farming Classification. Extensive livestock system. Reference: Newbould and Floate-2; Traditional hill sheep farming, U.K., Table 5. Hill farming is largely confined to areas above a b o u t 300m over most of the uplands in the U.K. b u t may extend almost to sea level in the west of Scotland and Ireland. The climate is typically hemiboreal to oro-hemi-arctic (Birse, 1971) with highest mean monthly temperatures in the range 10--15°C during a growing season of 180--200 days. The best soils are acid brown earths which carry an Agrostis--Festuca dominated grassland b u t such areas seldom represent more than 10--20% of a hill farm. Peaty podsols and peaty gleys are much more c o m m o n and t h e s e may carry heath dominated b y Nardus stricta and Molinia caerulea, or a shrub heath dominated by Calluna vulgaris. At the higher elevations ( > 5 0 0 m) or at lower elevations in the wettest areas deep peat with blanket bog is widespread. A typical hill farm unit in Scotland would cover some 1000--2000 hectares carrying 0.5--1 sheep ha -1 (Eadie and Maxwell, 1975). Farm units in other parts of the U.K. m a y be rather smaller and m a y include areas of c o m m o n grazing. Sheep are the most c o m m o n class of livestock b u t the better farms also carry cattle and a few specialise in hill cattle breeding. The main enterprise is the production of store lambs for cross breeding and for fattening on lower ground b u t some of the best lambs may be produced directly from the hills for meat. Wool production is mainly a by-product. As an example of such a system nutrient cycling data are given for a hill farm unit operated by the Hill Farming Research Organisation from 1954 to 1968. The system consisted of a 280-hectare unit which contained 90 hectares of dominantly Agrostis--Festuca grassland and 190 hectares of Nardus and Molinia dominated grass heath. The unit carried 387 ewes and the production averaged 90.6 lambs per 100 ewes. After 1968 the system was intensified and a description of that system follows in the next section.

6.2.2b. Improved hill sheep farming Classification. Extensive livestock system. Reference: Newbould and Floate-3; Improved hill sheep farming (whole system) (Table 7). Newbould and Floate-4; Hill grassland part of system N + F-3 (Table 8). Newbould and Floate-5; Improved paddock part of system N + F - 3 (Table 9). Data are first presented for the whole system (Table 7) and then for its c o m p o n e n t parts --hill grasslands (Table 8) and improved paddocks (Table 9). The natural and environmental resources of intensified hill farming systems are similar to those previously described. The difference is that selected areas are improved in order to provide better grass for livestock in the year-round

38

TABLE 5 System type: Extensive livestock

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -~ y - I )

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref. n o . N e w b o u l d a n d F l o a t e - 2

Traditional hill sheep farming, U.K.

Nutrient

N

P

K

Changes in a m o u n t of p l a n t c o m p o n e n t SUPPLIES :

29. 30t. 30r. 31.

Input by Transfer Transfer Input by

seeds or seedlings ............... by net uptake from soil ........... b y n e t u p t a k e f r o m soil . . . . . . . . . . . uptake from atmosphere .......... TOTAL

REMOVALS:

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. O u t p u t by p r i m a r y p r o d u c t s . . . . . . . . . . . . . . Transfer by plant production remaining on field . Transfer by seed for sowing .............. TOTAL

-44* --44

-3.8* --3.8

-13 + -(31)

-1.1 + -(2.7) -3.8

44

SUPPLIES-REMOVALS

0

-25* --25 7 + -(18) 25

0

0

Changes in a m o u n t o f a n i m a l c o m p o n e n t SUPPLIES:

1.

2. 3. 4. REMOVALS:

5. 6. 7. 8. 9.

Input by Input by Transfer Transfer

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

1" --13 + 14

. . .

Output by animal products ............... O u t p u t b y l o s s e s f r o m m a n u r e t o air, b e f o r e application ......................... Output by manure .................... Transfer by application of manure and/or waste . Transfer by d r o p p i n g s o n g r a z e d areas . . . . . . . TOTAL

1" ---(13) 14

SUPPLIES-REMOVALS

0

0.3 + --1.1 + 1.4 0.2* ---(1.2) 1.4

1" --7+ 8 t* ---(8) 8

0

0

Changes in amount of total soil component SUPPLIES:

REMOVALS:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27. 19. 20. 21. 22. 23. 28. 30.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... a p p l i c a t i o n o f litter~ s l u d g e a n d w a s t e . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . by seed for sowin .............. T~)gTAL

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... O u t p u t b y o r g a n i c m a t t e r , r e m o v e d b y r u n - o f f ~. . Transfer by net uptake from soil by plant ..... TOTAL SUPPLIES-REMOVALS

See 22.

-12 + 10 + 10 + 31 + 63 t t

-1.2 + -----0.4 + 2.7 + -4.5

14 + --

--0.4 + 0.4 + --

44* 61

3.8* 4.6

3+

+ 2

-0.3

-8+ --4+ 18 + 30 ---9+

2+ -25* 36 -

6

39

TABLE 5

(continued)

System type: Extensive livestock

Summary of n u t r i e n t f l o w s ( u n i t s : kg

T y p e o f f a r m or e c o s y s t e m or t y p e o f p a r t o f a f a r m o r e c o s y s t e m , ref. no. N e w b o u l d a n d F l o a t e - 2

ha -~

y-'

)

T r a d i t i o n a l hill s h e e p f a r m i n g , U.K.

Nutrient

N

P

K

C h a n g e s in a m o u n t o f available soil n u t r i e n t s SUPPLIES:

8a. 9a. 10a. 11. 12. 13a.

14. 15. 16. 17. 26a. 27. REMOVALS:

19. 20. 21. 22. 23. 24. 25. 30t. 30r.

Transfer Transfer Input by Input by I n p u t by Input by Input by I n p u t by Transfer Transfer Transfer Transfer

by application of manure and/or waste . b y d r o p p i n g s on g r a z e d areas . . . . . . . application of manure . . . . . . . . . ... fertilizers . . . . . . . . . . . . . . . . . . . . N-fixation a p p l i c a t i o n o f litter, sludge a n d w a s t e . irrigation and flooding . . . . . . . . . . . dry and wet deposition ........... b y w e a t h e r i n g o f soil m i n e r a l f r a c t i o n . . by m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n b y p l a n t p r o d u c t i o n r e m a i n i n g on field . b y seed f o r s o w i n g . . . . . . . . . . . . . . TOTAL

Output by denitrification ................ O u t p u t by volatilization of a m m o n i a . . . . . . . . Output by leaching . . . . . . . . . . . . . . . . . . . . O u t p u t by r u n - o f f o f available n u t r i e n t s . . . . . . O u t p u t by d u s t . . . . . . . . . . . . . . . . . . . . . . T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n Transfer by net uptake by the plant . . . . . . . . . T r a n s f e r by n e t u p t a k e b y t h e p l a n t TOTAL SUPPLIES-REMOVALS

--8+

t+

--7+

---

---

---

10 + --

--

--

--

-4+

10 + -17 --29 t t

3+

-t -pro,44

0.4 + pm pm --0.4 --0.4 + 0.1 + t pm Pro8*3.

Pl+m 18 + -30 -9+ 2+ t pm

-47

-4.6

-36

-18

-4.2

-

6

C h a n g e s in a m o u n t o f soil o r g a n i c m a t t e r SUPPLIES:

8b. 9b. 10b.

13b. 25. 26b. REMOVALS:

17. 28.

Transfer Transfer Input by Input by Transfer Transfer

by a p p l i c a t i o n a n d / o r w a s t e . . . . . . . . b y d r o p p i n g s on g r a z e d areas . . . . . . . application of manure ............ a p p l i c a t i o n o f litter, s l u d g e a n d w a s t e . b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n by p l a n t p r o d u c t s r e m a i n i n g on field . . TOTAL

T r a n s f e r b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n O u t p u t by o r g a n i c m a t t e r , r e m o v e d b y r u n - o f f . . TOTAL SUPPLIES-REMOVALS

4+ -m P31 + 35 1? 14 15 +20

C h a n g e s in a m o u n t o f soil m i n e r a l s SUPPLY: REMOVAL:

24. 16.

T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y w e a t h e r i n g o f soil f r a c t i o n . . . . . . . SUPPLY-REMOVAL

---

1+ 1.2 + --m P2.7 + 3.9 pm -0 3.9

---1 1 t 1 0

40

N O T E S T O T A B L E 5. (Reference Newbould and Floate-2) 1. Bought-in food consists of 7 kg concentrate plus 17 kg hay per ewe. 4. Plant dry matter production is assumed to be 2500 kg ha -I from Agrostis--Festuca grassland and 2000 kg ha -I from Nardus--Molinia grass heath. W e have assumed 4 0 % utilisation of Agrostis--Festuca and 2 0 % utillsation of Nardus--Molinia. S u m m e r and winter consumption are assumed to be equally divided and the following data for mineral composition (Floate, unpublished data) have been used in the calculations: Agrostis--Festuca summer winter

N = 3.0%; P = 0.30%; K = 2.2% d.m. N -- 2.0%; P = 0.15%; K = 0.7%.

Nardus--Molinia summer N = 2.0%; P = 0.20%; K -- 1.5%. winter N = 1.5%; P = 0.10%; K -- 0.5%. 5. Sales c o n s i s t of: 5 7 3 2 kg l a m b = 20 kg h a -~ at N = 2.81%; P = 0.65%; K = 0.18% ~ 69 cast ewes = 13 k g h a -~ at N 1.53%;P 0 . 5 5 % ; K = 0.14% ) 8 0 0 kg w o o l -- 2.8 kg h a -~ at N = 17.8%

S y k e s a n d Field (1972) Ryder and Stephenson (1968)

9. E x c r e t a r e t u r n s have b e e n c a l c u l a t e d as d e s c r i b e d previously. 12. N f i x a t i o n is an e s t i m a t e b a s e d o n J e n k i n s o n ( u n p u b l i s h e d data, 1975). 15. D a t a h a v e b e e n t a k e n f r o m p u b l i s h e d r e p o r t s for o t h e r u p l a n d areas in t h e U.K. (Crisp, 1 9 6 6 ; Gore, 1 9 6 8 ; a n d Allen e t al., 1 9 6 8 ) . 17. M i n e r a l i z a t i o n d a t a used refer t o release o f n u t r i e n t s f r o m freshly d e p o s i t e d faeces a n d p l a n t residues a n d as s u c h d o n o t take a c c o u n t o f release f r o m soil organic sources. F o r this r e a s o n t h e e s t i m a t e s m a y be low b u t t h e w h o l e s y s t e m is p r o b a b l y close t o s t e a d y s t a t e a n d it is d o u b t f u l if organic m a t t e r levels u n d e r very old grassland are c h a n g i n g a p p r e c i a b l y ; t h e e s t i m a t e s m a y t h e r e f o r e b e r e a s o n a b l e b u t even if o n l y 0.1% o f t h e organic N in soil is m i n e r a l i s e d this c o u l d release u p t o 10 kg h a -~ y-~ and m a t e r i a l l y c h a n g e t h e overall balance. Basic d a t a used are f r o m F l o a t e ( 1 9 7 0 ) for d e c o m p o s i t i o n o f organic materials, i n c u b a t ed for 12 w e e k s at 10°C. T h e p e r c e n t a g e s o f original c o n t e n t s released (+) o r i m m o b i l i z e d (--) are: Faeces Plant litter

Agrostis--Festuca Nardus--Molinia

+ 7.6% N + 2.2% P + 9.8% N + 2.8% P

+ 1.2% N - - 29% P + 0.6% N - - 24% P

We h a v e also a s s u m e d t h a t as K does n o t e n t e r i n t o organic c o m b i n a t i o n it is likely t o b e released a t a b o u t t h e s a m e rate as C, i.e. Agrostis--Festuca 30%; Nardus 20%;Agrostis-Festuca faeces 2%; Nardus faeces 2%. S h a w ( 1 9 5 8 ) s h o w e d t h a t s o m e 2--6% o f t h e organic N in t h e m a t layers o f hill soils c o u l d b e m i n e r a l i z e d a n d this h a s b e e n c a l c u l a t e d t o yield s o m e 3 0 - - 6 0 kg h a -1 m i n e r a l N. T h i s is o f t h e o r d e r r e q u i r e d t o s u p p l y N for p l a n t u p t a k e w h i c h does n o t s u b s e q u e n t l y f o l l o w t h e a n i m a l p a t h w a y b u t r e t u r n s t o soil as p l a n t litter. 19. D e n i t r i f i c a t i o n losses are p r o b a b l y small b e c a u s e these are a c c e l e r a t e d b y high organic m a t t e r c o n t e n t , NO3-N, pH a n d t e m p e r a t u r e , o f w h i c h t h e last t h r e e are f r e q u e n t l y low in hill soils. 20. Volatile a m m o n i a losses m a y also b e small b e c a u s e o f h i g h m o i s t u r e c o n t e n t o f t h e soil a n d l o w pH. H o w e v e r , a p p r e c i a b l e losses m a y o c c u r f r o m d e c o m p o s i n g faeces a n d f r o m u r i n e patches. 21. L e a c h i n g losses are c i t e d f r o m Crisp (1966). 22. Drainage losses (Crisp, 1 9 6 6 ) i n c l u d e e r o s i o n o f p e a t a n d this o n l y f o r m s a very small

41

TABLE 6 Management of stock in relation to improved and unimproved hill pasture Time

Production period

Improved hill

Unimproved hill

Mid-January to

Pregnancy

Rested

Lactation

Nursing ewes

Breeding sheep storm feeding -- hay, beet pulp Pre-lamb feeding of concentrates Dry sheep and hoggs

Late lactation and

Dry sheep and

mid-April March/April Mid-April to mid-July Mid-July to mid-August Mid-August to early October Early October to mid-December

early body weight recovery Body weight recovery Body weight recovery

hoggs Rested All breeding sheep

Nursing ewes to weaning All breeding sheep and stock ewe lambs Ewe hoggs

Tupping Mid-December to mid-January

Close of tupping

Rested

All breeding sheep

cycle of nutrition, but with special emphasis on the mating and post.lambing periods. Selected areas may be improved by fencing and grazing control but more commonly surface improvements including lime, phosphate and over-sowing with grass and clover would be employed. Such improved areas might extend to 20--30% of the whole unit and would be grazed to maximise utilisation during the critical nutritional periods (Table 6 shows a typical management timetable). Such systems thus contain two sul>systems, one of which consists of improved grassland while the other consists of unimproved hill land. Systems of this type are not common in farm practice except at research and development centres, but their number is rapidly increasing. It should be noted that many hill farms consist of open hill land together with small grass fields but the management of these resources differs widely from the intensified system described here. Nutrient cycling data are given for the same 280-hectare unit described under traditional management but which has been operated from 1968 to 1975 as an intensified system. In 1974/1975 the system consisted of 90 hectares enclosed paddocks (of which 36 ha had received lime and P) together part of the area in this system. These values may therefore be in excess of the true losses. 26. Calculated by difference between uptake (30) and consumption by grazing (4). All nutrients in plant litter assumed organic (Pool B) until released by mineralization. 30. Nutrient uptake calculated from yield and composition data given in note 4. No data are available for roots.

42

TABLE

7

System type: Extensive livestock

S u m m a r y of nutrient flows (units: kg ha -I y-l )

Type of farm or ecosystem or type of part of a farm or ecosystem, ref.no. Newbould and F l o a t e - 3

Improved hillsheep farming, paddock + hill grassland, U.K.

Nutrient

N

P

K

-52*

-5.4* --5.4

-38*

-3.0 + -(2.4) -5.4

-21 +

Changes in amount of plant component SUPPLIES:

REMOVALS:

29. 30t. 30r. 31. 3. 4. 18. 26. 27.

Input by Transfer Transfer Input by

seeds or seedlings ............... by net uptake from soil ........... by net uptake from soil ........... uptake from atmosphere .......... TOTAL

52

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by plant production remaining on field . Transfer by seed for sowing .............. TOTAL

-31 + (21) 52

SUPPLIES-REMOVALS

0

-38

(17) 38

0

0

Changes in amount of animal component SUPPLIES:

REMOVALS:

1. 2. 3. 4.

Input by Input by Transfer Transfer

5. 6.

Output by animal products ............... O u t p . u t b y l o s s e s f r o m m a n u r e t o air, b e f o r e application ......................... Output by manure .................... Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s o n g r a z e d areas . . . . . . . TOTAL

7. 8. 9.

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

. . .

2+ --31 + 33

0.3 + --3.0 + 3.3

1+ --21 + 22

3*

0.4*

1"

t ---

----

----

(30)

(2.9)

(21)

33

3.3

22

SUPPLIES-REMOVALS

0

0

0

Changes in a m o u n t o f t o t a l soil c o m p o n e n t SUPPLIES:

REMOVALS:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer by application of manure and/or waste . Transfer by d r o p p i n g s on grazed areas . . . . . . . Input by application of manure ............ Input by fertilizers .................... Input by N-fixation .................... I n p u t b y a p p l i c a t i o n o f litter~ s l u d g e a n d w a s t e . Input by imgation and flooding ........... Input by dry and wet deposition ........... Transfer by plant products remaining on field . . Transfer by seed for sowing .............. TOTAL

19. 20. 21. 22. 23. 28. 30.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... O u t p u t b y o r g a n i c m a t t e r , r e m o v e d b~" r u n - o f f . . Transfer by net uptake from soil by plant ..... TOTAL SUPPLIES-REMOVALS

-30 + 10 + 10 + 21 + 71 t t

-2.9 + -5.1" ---

-21 + ----4+

0.4 + 2.4 + -10.8

17 + 42

--

--

0.4 + 0.4 + --

--9 + 2 --

5.4* 6.2

38* 49

3+ 14? --52* 69

+ 2

+4.6

-

7

43

TABLE

7

(continued)

System type: Extensive livestock

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -~ y - ~ )

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no. Newbould and Floate-3

I m p r o v e d hill s h e e p f a r m i n g , p a d d o c k grassland, U.K.

Nutrient

N

Changes in amount SUPPLIES:

REMOVALS:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer Transfer Transfer

19. 20. 21. 22. 23. 24. 25. 30t. 30r.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... T r a n s f e r b y f i x a t i o n in s o i l m i n e r a l f r a c t i o n . . . . Transfer by immobilization in soil organic fraction Transfer by net uptake by the plant ......... Transfer by net uptake by the plant ......... TOTAL

Changes in amount

REMOVALS:

8b. 9b. 10b. 13b. 25. 26b. 17. 28.

by application of manure and/or waste . by droppings on grazed areas ....... application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . im'gation and flooding ........... dry and wet deposition ........... by weathering of soil mineral fraction.. by mineralization of soil organic fraction by plant production remaining on field . by seed for sowing .............. TOTAL

C h a n g e s in a m o u n t 24. 16.

-20 + --10 + -10 + -17 --41

t+ -5.1" ----

21 + -----

0.4 +

4+

pm t --5.5

pm

---9+

Pm,52

--0.4 + 0.4 + -pm Pm4*5.

-69

-6.2

38* -49

-28

-0.7

-

2.9 + --m P2.4 + 5.3

--0 + ---

t t

3+ 14 + --

17 + -42

2+ -pm

7

of soil organic matter Transfer Transfer Input by Input by Transfer Transfer

by application and/or waste ........ by droppings on grazed areas ....... application of manure ............ application of litter, sludge and waste . by immobilization in soil organic fraction by plant products remaining on field . . TOTAL

Transfer by mineralization of soil organic fraction Output by organic matter, removed by run-off . . TOTAL SUPPLIES-REMOVALS

SUPPLY: REMOVAL:

K

o f a v a i l a b l e soil n u t r i e n t s

SUPPLIES-REMOVALS

SUPPLIES:

P

+ hill

-10 + -m P21 + 31 1+ -1 +30

of soil minerals Transfer by fixation in soil mineral fraction .... T r a n s f e r b y w e a t h e r i n g o f soil f r a c t i o n . . . . . . . SUPPLY- REMOVAL

--

t t t +5.3

-0 --0

44

TABLE 8 System type: Extensive livestock

Summary of . n u t r i e n t f l o w s ( u n i t s : k g h a -~ y - i )

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref. n o . N e w b o u l d a n d F l o a t e - 4

Improved hill sheep farming U.K. Hill grassland part of Newbouldand Floate-3

Nutrient

N

P

K

C h a n g e s in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

REMOVALS:

29. 30t. 30r. 31. 3. 4. 18. 26. 27.

Input by seeds or seedlings ............... Transfer by net uptake from soil ........... Transfer by net uptake from soil ........... Input byuptake from atmosphere .......... TOTAL

-35* --

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by plant production remaining on field . Transfer by seed for sowing .............. TOTAL

20* --

35

3.0* --3.0

-18 + -(17) "-- " 35

-1.5 + -(1.5) -3.0

-10 + -(10) -20

SUPPLIES-REMOVALS

0

20

0

0

Changes in amount of animal component SUPPLIES:

REMOVALS:

1.

Input by feed for livestock . . . . . . . . . . . . . . .

2. 3. 4.

Input by litter used indoors .............. Transfer by consumption of harvested crops Transfer by grazing of forage ............. TOTAL

5. 6.

Output by animal products ............... O u t p u t b y losses f r o m m a n u r e t o air, b e f o r e application ...... ................... Output by manure .................... Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s o n g r a z e d areas . . . . . . . TOTAL

7. 8. 9.

2** --18 + 20

. . .

0.3**

1.3"* t --(19) 20

SUPPLIES-REMOVALS

1"*

--1.5 + 1.8

--10 + 11

0.2** ---(1.6) 1.8

0

1"* ---(10) 11

0

0

Changes in a m o u n t o f t o t a l soil c o m p o n e n t SUPPLIES:

REMOVALS:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

19. 20. 21. 22. 23. 28.

Output by denitrification ................ Output by volatilization of ammonia ........ O u t p u t b y l e a c h i n g . ~. . . . . . . . . . . . . . . . . . . Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off Transfer by net uptake from soil by plant ..... TOTAL

30.

by application of manure and/or waste . by d r o p p i n g s on grazed areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . by seed for sowing .............. TOTAL

SUPPLIES-REMOVALS

-19 + --

-1.6 + -----

---

10 + 17 + -51

0.4 + 1.5 -3.5

4+ 10 + -24.7

t

--

--

t

--

--9+

0.4 + 0.4 + --

--

35* 52

3* 3.8

20* 31

1

-0.3

5+

3+ 14? -. .

-10.7 + --

2+

--

-

**Arbitrarily derived from Newbould and Floate-3 (assumed 1/4 paddock, 3/4 grassland) by editor for classification purposes.

-

6.3

45

TABLE

8

(continued)

System type: Extensive livestock

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -1 y - i )

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no. Newbould and Floate-4

I m p r o v e d hill s h e e p f a r m i n g U . K . Hill grassland part of Newbould and Floate-3

Nutrient

N

C h a n g e s in a m o u n t SUPPLIES:

REMOVALS:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer Transfer Transfer

by application of manure and/or waste . by droppings on grazed areas ....... application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by weathering of soil mineral fraction.. b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n by plant production remaining on field . by seed for sowing .............. TOTAL

19. 20. 21. 22. 23. 24. 25. 30t. 30r.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y i m m o b i l i z a t i o n i n soil o r g a n i c f r a c t i o n Transfer by net uptake by the plant ......... Transfer by'net uptake by the plant ......... TOTAL SUPPLIES-REMOVALS

Changes in amount SUPPLIES:

REMOVALS:

8b. 9b. 10b. 13b. 25. 26b. 17. 28.

C h a n g e s in a m o u n t 24. 16

K

-13 + -5+ -10 + -17 --29

t+ -----0.4 + pm t --0.4

t t

11 + ---4+ pm 10 + -25

--

--

3+ 14 + --

0.4 + 0.4 + -pm

--9 + 2+ -pm

P~n5+ -52

P~.0 + -3.8

20 + -31

-23

-3.4

-

6

o f soil o r g a n i c m a t t e r Transfer Transfer Input by Input by Transfer Transfer

by application and[or waste ........ by droppings on grazed areas ....... application of manure ............ application of litter, sludge and waste . b y i m m o b i l i z a t i o n in s o i l o r g a n i c f r a c t i o n by plant products remaining on field . . TOTAL

"Transfer by mineralization of soil organic fraction Output by organic matter, removed by run-off.. TOTAL SUPPLIES-REMOVALS

SUPPLY: REMOVAL:

P

o f a v a i l a b l e soil n u t r i e n t s

--6+

SUPPLY-REMOVAL

--m Pl.5 + 3.1

---

1

t

1

t

----

--

--

+22

o f soil m i n e r a l s T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . Transfer by weathering of soil fraction .......

0+ 1.6 +

--m P17 + 23

---

+3.1

0

0

46

TABLE 9 System type: Extensive livestock

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -1 y - i )

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no. Newbould and Floate-5

I m p r o v e d hill s h e e p f a r m i n g , U . K . Paddock part of Newbould and Floate-3

Nutrient

N

C h a n g e s in a m o u n t SUPPLIES:

REMOVALS:

29. 30t. 30r. 31. 3. 4. 18. 26. 27.

SUPPLIES:

1. 2.

3. 4.

REMOVALS:

5. 6. 7.

8. 9.

K

of plant component Input by Transfer Transfer Input by

seeds or seedlings ............... by net uptake from soil ........... by net uptake from soil ........... uptake Irom atmosphere .......... TOTAL

-105" --

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by plant production remaining on field . Transfer by seed for sowing .............. TOTAL

77* --

105

10.5" --10.5

-60 + -(45) -105

--6 + -(4.5) -10.5

44 +

0

0

SUPPLIES-REMOVALS C h a n g e s in a m o u n t

P

77

(33) -77 0

of animal component Input by Input by Transfer Transfer

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

0"* --60 + 60

. . .

Output by animal products ............... O u t p u t b y l o s s e s f r o m m a n u r e t o air, b e f o r e application~ll . . . . . . . . . . . . . . . . . . . . . . . . . Output by manure .................... Transfer by application of manure and/or waste . Transfer by droppings on grazed areas ....... TOTAL

0"* --6.0 + 6.0

8** t

1.2"* --

---

(4.8)

60

SUPPLIES-REMOVALS

6.0

0

4** --

-- -

(52)

0"* --44 + 44

-(40)

44

0

0

C h a n g e s in a m o u n t o f t o t a l s o i l c o m p o n e n t SUPPLIES:

REMOVALS:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

19. 20. 21. 22. 23. 28.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off.. T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL

30.

by application of manure and/or waste . by droppings on grazed areas ....... application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irn'gation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . by seed for sowing .............. TOTAL

SUPPLIES-REMOVALS **

Arbitrarily derived from Newbould editor for classification purposes.

-52 + -15" -10 + 45 + -122 t t

-4.8 + -16" ---0.4 + 4.5 + -25.7

4 ++ 3 -77

--

--

3+

14? --

-40 + --

0.4 +

---

--9 +

0.4 +

2+

--

--

--

--

1"05 122

10.5 11.3

77 88

0

+14.4

-11

and Floate-3 (assumed 1/4 paddock, 3/4 grassland) by

47

TABLE

9

(continued)

System type: Extensive livestock

S u m m a r y of nutrient flows (units: kg ha -~ y-1 )

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no. Newbould and Floate-5

Improved hillsheep farming, U.K. Paddock part of Newbould and Floate-3

Nutrient

N

P

K

Changes in amount of available soil nutrients SUPPLIES:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

R E M O V A L S : 19. 20. 21. 22. 23. 24. 25. 30t. 30r.

Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s on grazed areas . . . . . . . I n p u t by application o f m a n u r e . . . . . . I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . . I n p u t b y N-fixation . . . . . . . . . . . . . . . . . . . . I n p u t b y a p p l i c a t i o n o f litter, sludge and w a s t e . I n p u t by irrigation a n d flooding . . . . . . . . . . . I n p u t b y d r y and w e t d e p o s i t i o n . . . . . . . . . . . T r a n s f e r b y w e a t h e r i n g o f soil m i n e r a l f r a c t i o n . . T r a n s f e r by m i n e r a l i z a t i o n o f soil organic fraction T r a n s f e r by p l a n t p r o d u c t i o n r e m m m n g on field . T r a n s f e r b y seed for s o w i n g . . . . . . . . . . . . . . TOTAL O u t p u t by d e n i t r i f i c a t i o n . . . . . . . . . . . . . . . . O u t p u t b y volatilization o f a m m o n i a . . . . . . . . O u t p u t by leaching . . . . . . . . . . . . . . . . . . . . O u t p u t by r u n - o f f o f available n u t r i e n t s . . . . . . O u t p u t by d u s t . . . . . . . . . . . . . . T r a n s f e r b y fixation in soil m i n e r a l fraction . . . . T r a n s f e r b y i m m o b i l i z a t i o n in soil organic fraction Transfer by net uptake by the plant . . . . . . . . . Transfer by net uptake by the plant . . . . TOTAL

SUPPLIES-REMOVALS

-.

36 + . .

.

15" .

.

-10 + -2? .

.

63 t t

3*

t+ . . . 16" -. -0.4 + pm t . -16.4

40 + . --4+ pm 33 + 77

---

--

+ 5.1

-11

9+ 0.4 + 14? 0.4 + 2+ . . . . . . . . . . . . pm pm pm 105" P~n0.5* 77* . . . . . . . 122 11.3 88

- 59

Changes in amount of soil organic matter SUPPLIES:

8b. Transfer by application and/or waste . . . . . . . . . . 9b. T r a n s f e r b y droppings on grazed areas . . . . . . . 16 + 4.8 . . . . . . . . . . . . . 13b. I n p u t b y application o f litter, sludge a n d w a s t e . . . . 25. T r a n s f e r b y i m m o b i l i z a t i o n in soil organic fraction p m pm 26b. T r a n s f e r b y p l a n t p r o d u c t s r e m a i n i n g on field . . 45 4.5 TOTAL 61 9.3

10b. I n p u t b y application o f m a n u r e .

R E M O V A L S : 17. 28.

T r a n s f e r by m i n e r a l i z a t i o n o f soil organic fraction O u t p u t b y organic m a t t e r , r e m o v e d b y r u n - o f f . TOTAL SUPPLIES-REMOVALS

2 . + 59

Changes in a m o u n t o f soil minerals SUPPLY: REMOVAL:

24. 16.

T r a n s f e r b y fixation in soil m i n e r a l fr~ction . . . . . T r a n s f e r b y w e a t h e r i n g o f soil fraction . . . . . . . -SUPPLY- REMOVAL

. 2

t . t

--0 + . --0

.

+ 9.3

0 --

48

with the original 190 hectares of hill grass-heath. The system now carries 601 e w e s p r o d u c i n g 1 0 2 . 7 l a m b s p e r 1 0 0 e w e s . P r o d u c t i o n is a l m o s t d o u b l e t h a t from the traditional system. The system also carries a small number of cattle but these are mainly used to clean up uneaten herbage on the production paddocks and this does not materially affect the data given in the nutrient b a l a n c e t a b l e . T h i s s y s t e m h a s r e c e n t l y b e e n d e s c r i b e d b y E a d i e e t al. ( 1 9 7 7 ) .

N O T E S T O T A B L E S 7--9. (References Newbould and Floate-3 to-5) 1. Bought-in feed was increased mainly to supplement intake during pregnancy, especially of hoggs and ewes carrying twins (only applicable to whole farm systems) (for classification purpose by the editor, listed as input in Table 8). 4. Plant dry matter production from improved paddocks taken as 3500 kg ha -I and from hill grasslands as 2000 kg ha -I. Composition data from our o w n analysis: Improved paddocks, N = 3.0%; P = 0.3%; K = 2.2%. Nardus--Molinia

summer N = 2.0%; P -- 0.2%; K = 1.5%. winter N = 1.5%; P = 0.1%; K = 0.5%. Grazing utilisation percentages used for the sub-systems are 57% and 50% for the paddocks and hill grasslands, respectively. 5. Production consists of 617 lambs weaned, 461 lambs sold = 11986 kg, 107 cast ewes sold and 1535 kg wool sold.Composition data as used in previous section (for classification purposes arbitrarily split by the editor as outputs of Tables 8 and 9 ; the splitting is based on the ratio between the areas, the grazing period and fertility status of the system). 9. Excreta return has been calculated for each sub-system and combined for the whole farm system. Partitioning between faeces and urine was calculated as in the previous section. Urine components are taken as available (9a). Faeces components are considered organic (9b) until released by mineralization. 11. Lime (6000 kg ha -~) and basic slag (1250 kg ha -~, 6.5% P ) h a v e been applied to 36 ha of the enclosed paddocks, and it is assumed that maintenance dressings will be applied on a five-year cycle. Accordingly, fertilizer P has been calculated assuming that 90 ha will receive 80 kg ha -~ P once in five years or 16 kg ha -~ y-1. Over the whole system this has been expressed as 5.1 kg ha -~ y-~. 12. Estimated amounts of N fixed range from 10--20 kg ha -~ for enclosed paddocks which m a y include a small proportion of clover, to 5--10 kg ha -~ for hill areas where only nonsymbiotic fixation is considered. 15. See notes for Traditional hillsheep system. 17. See notes for Traditional hill sheep system. 19, 20. Likely to be very small for reasons discussed under Traditional hillsheep system. 21, 22. See notes for Traditional hillsheep system. Losses are assumed to be uniform over whole farm but this is unlikely to apply in practice; in particular, run-off losses (22) are probably too high. 26. Calculated by the difference between uptake (30) and consumption by grazing (4). All nutrients in the plant litterare assumed organic (pool b) until released by mineralization. 30. Plant d.m. production from enclosed paddocks has increased to about 3500 kg ha -I. Nutrient uptake is calculated using the following composition for improved pasture: N = 3.0%; P = 0.3%; K = 2.2% (Floate, unpublished data). Other data used to calculate uptake are given under note (4).

49

6.2.3. Systems with forestry Classification. Extensive forestry system. Reference: N e w b o u l d and Floate-6; Meathop Wood, U.K., Table 10. The forests managed by the Forestry Commission are predominantly coniferous and are located throughout the United Kingdom, with the largest proportion (61%) in Scotland. Of the total 1.2 X 106 ha, 25% is in England and the remaining 14% is in Wales. Most of the forests are on the poorer softs in the higher and wetter northern and western regions of the country. The predominant under-lying soils are strongly podsolized or gleyed, and most have a peaty surface horizon. In the establishment of such commercial forests (frequently on former marginal agricultural land), attention is paid to improving adverse drainage conditions and minimising plant competition b y the use of special cultivation methods. Phosphorus and potassium fertilizer is added either uniformly over the whole area to be planted or, more c o m m o n l y now, to the vicinity of each seedling tree. T o p dressing of phosphate 6--7 years after planting is often practised. It is generally accepted that the critical time nutritionally for y o u n g trees lasts until the canopies meet at 10--12 years. Provided that the trees are in nutrient balance at this time, the system is usually maintained without further additions of fertilizer b y natural cycling processes. There is a much smaller area (200 000 ha) of private mixed woodland, and the best data on nutrient cycling available to us refer to a woodland ecosystem within this group. We have taken as an example of a woodland ecosystem the main U.K. site for study in the IBP Woodland Biome. The following description has been given by Satchell (1971): "Meathop Woods, covering approximately 40 hectares, lie three kilometres from Grange-over-Sands on the sea coast of Morecambe Bay on the southern edge of the English Lake District. They are situated at an altitude of about 45 metres on an outcrop of Carboniferous limestone with terraces and small scarps. The terraces are covered with glacial drift of a mean depth in the study area of 38 cm, but varying greatly with the eroded surface of the underlying limestone pavement. The soil is predominantly brown earth with a mull humus, the pH of the A horizon in the study area ranging from 4.1 to 7.3. Meathop Wood is a mixed deciduous wood with oak, ash, birch and s y c a m o r e dominating the canopy and hazel forming a well-developed understorey. The ground layer is dominated by Rubus fruticosus agg., Endymion non-scriptus, Anemone nemorosa, Mercurialis perennis and Oxalis acetosella. There is a recorded history of woodland management, mainly for charcoal production, since 1770, and the site is thought to have carried woodland indefinitely. Rainfall is approximately 120--125 cm per annum."

The nutrient balance calculations suggest a gain in soil-N which is probably apparent rather than real because there are incomplete data for gaseous exchange. The authors state that it is n o t possible to say whether the system is in equilibrium with respect to N. Their scheme suggests that the system as a whole appears to gain 103 kg N ha -1 per year, of which 78 kg ha -1 y-~ is appar-

50

T A B L E 10 System type: Forest

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -~ y-~ )

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref. n o . N e w b o u l d a n d F l o a t e - 6

Meathop Wood, U.K. (Interpretation, Ulrich)

Nutrient

N

P

K

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

29. 30t. 30r.

31. REMOVALS:

3. 4. 18. 26. 27.

Input by Transfer Transfer Input by

seeds or seedlings . . . . . . . . . . . . . . . by net uptake from soil ........... by net uptake from soil ........... uptake from atmosphere .......... TOTAL

--

--

97 70 9 176

Transfer by consumption of harvested crops . . . -Transfer by grazing of forage ............. -Output by primary products .............. 9 Transfer by plant production remaining on field . ~ 97 55 Transfer by seed for sowing .... .......... TOTAL 161 (Root increment)

SUPPLIES-REMOVALS

+ 15

-10.8"

-54 23 -77

---

---

7.9 2.9

0.8 7.1 2.3

6 48 16

10.2

70

+ 0.6

+ 7

Changes in amount of animal component SUPPLIES:

1. 2. 3.

4. REMOVALS:

5. 6. 7.

8. 9.

Input by Input by Transfer Transfer

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

. .

.

Output by animal products ............... O u t p u t b y l o s s e s f r o m m a n u r e t o air, b e f o r e application ......................... Output by manure .................... Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s o n g r a z e d areas . . . . . . . TOTAL

--

SUPPLIES-REMOVALS C h a n g e s in a m o u n t o f t o t a l s o i l c o m p o n e n t SUPPLIES:

REMOVALS:

8. 9. 10. 11. 12. 13. 14. 15. 26.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . ~

27.

Transfer by seed for sowing .............. TOTAL

19. 20. 21. 22. 23. 28. 30.

Output by denitrification ................ Output by volatilization of amm6nia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off . . Transfer by net uptake from soil by plant ..... TOTAL SUPPLIES-REMOVALS

----100 --

-------

6 97 55

0.4 7.1 2.3

258 t t 13 ---167 180 + 78

-------

9.8

6 48 16 70

---

---

0.3 ---10.8 11.1

8 ---77 85

-

1.3

-15

51

T A B L E 10 ( c o n t i n u e d ) System type: Forest

Summary of n t / t r i e n t f l o w s ( u n i t s : k g h a -1 ' y - I )

T y p e o f f a r m or e c o s y s t e m o r t y p e o f p a r t o f a f a r m or e c o s y s t e m , ref. no. N e w b o u l d a n d F l o a t e - 6

M e a t h o p W o o d , U.K. (Interpretation, Ulrich)

Nutrient

N

P

K

C h a n g e s in a m o u n t o f available soil n u t r i e n t s SUPPLIES:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

R E M O V A L S : 19. 20. 21. 22. 23. 24. 25. 30t. 30r.

Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s on g r a z e d areas . . . . . . . Input by application of manure ............ I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . Input by N-fixation .................... I n p u t by a p p l i c a t i o n o f litter, s l u d g e a n d w a s t e . Input by irrigation and flooding . . . . . . . .... Input by dry and wet deposition ........... T r a n s f e r b y w e a t h e r i n g o f soil m i n e r a l f r a c t i o n . . T r a n s f e r b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g on field . Transfer by seed for sowing . . . . . . . . . . . . . . TOTAL O u t p u t by d e n i t r i f i c a t i o n . . . . . . . . . . . . . . . . O u t p u t by volatilization of a m m o n i a . . . . . . . . O u t p u t by leaching . . . . . . . . . . . . . . . . . . . . O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . Output by dust ...................... T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n Transfer by net uptake by the plant . . . . . . . . . T r a n s f e r b y n e t d p t a k e b~v ~ e p l a n t ......... TOTAL

---

--------

-100 -6 -121 --

------

0.4 pm 8.2 --8.6

227 t t

6 pm 64 -70

---

---

13

0.3

8

97 70 180

-pm -7.9 2.9 11.1

-54 23

--

SUPPLIES-REMOVALS

47

--

85

2.5

-

-15

C h a n g e s in a m o u n t o f soil o r g a n i c m a t t e r SUPPLIES:

8b. 9b. 10b. 13b. 25. 26b.

Transfer Transfer Input by Input by Transfer Transfer

by a p p l i c a t i o n a n d / o r w a s t e . . . . . . b y d r o p p i n g s on g r a z e d areas . . . . . . . -application of manure ............ -application o f litter, sludge and waste . by i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n . . . ~ 97 b y p l a n t p r o d u c t s r e m a i n i n g on field . . ~ 1 5 5

17. 28.

T r a n s f e r b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n O u t p u t by organic matter, removed by r u n - o f f . . TOTAL

TOTAL REMOVALS:

SUPPLIES-REMOVALS

.

.

.

.

---

. ---

7.1 2.3

48 16

152

9.4

64

121 -121

8.2 -8.2

64 -64

+ 31

+ 1.2

0

C h a n g e s in a m o u n t o f soil m i n e r a l s SUPPLY: REMOVAL:

24. 16.

T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . . T r a n s f e r b y w e a t h e r i n g o f soil f r a c t i o n . . . . . . . -SUPPLY-REMOVAL

pm pm 0

0

pm

52

ently accumulated in the soil. This latter figure agrees with the present interpretation of the data*. Our calculations suggest a net loss of 1.3 kg P ha -~ per year from the soil, which contrasts with an apparent net gain of 0.11 kg P ha -~ per year in the whole system (White and Harrison). The difference between these calculations is largely accounted for by incremental gain in the production compartment. A fundamental difference between agricultural production systems and woodlands is the accumulation of nutrients in the living trees. White and Harrison indicate that some 24 kg N, 1.4 kg P and 13 kg K ha -1 y-~ are incorporated into the standing crop and are lost from the soil for the lifetime of the tress. In the data in Table 10, these amounts are divided between stems (which are eventually lost from the system as product) and r o o t increment (which is accounted as a gain in the plant component). In both our calculations, and in the White and Harrison presentation, the soil appears to be in K deficit b u t this is probably made good by weathering of K from rocks (no data are available for 16). The authors concluded that " t h e only element amongst those sampled (N, P, K, Ca, Mg, Na) which is likely to cause stress to the system is phosphorus". NOTES TO TABLE 10. (Reference Newbould and Floate-6) The data used here have been taken from a draft manuscript of the chapters by Harrison, and by White and Harrison in a volume entitled "Studies o f an English Oak Woodland" (in preparation). 12. N-fixation estimate from Dr B.T. D'Sylva's laboratory studies. White and Harrison (loc. cit.) observe that this may be high but cite data of Jenkinson (1971) w h o showed that when arable soil was allowed to revert to deciduous woodland, 65 kg ha -1 y-I N accumulated in the soil over a period of 81 years. 15. Data from White and Harrison (loc. cit.). 17. Mineralization data from White and Harrison for N and P : K mineralized + K humified has been used here for mineralization since it is thought unrealistic to consider humification of K. 18. Primary products consist o f stems of trees only: stem increment of production from White and Harrison (loc. cit.). 21. Leaching data from White and Harrison (loc.cit.). 25. White and Harrison give data for humification but in our presentation the amounts included here are accounted as litter (26): humification appears in the balance as net gain in the soil organic pool. 26. Divided into (26t) which includes all tree and herb litter, and (26r) which is root death; data from White and Harrison (loc. cit. ). 30. Net nutrient uptake interpreted from White and Harrison's data using the followiDg assumptions: 30r = root death + root production increment. 30t = total uptake by trees and herbs less root uptake and net of loss by stem and leaf leaching. 31. Atmospheric interception by trees does not include leaching from trees or stem wash. *Newbould and Floate are greatly indebted to White and Harrison for permission to use their da'ta, and to Ulrich and to Harrison who later assisted in interpretation.

53

6.2.4. Systems with intensive grassland husbandry Such systems in the U.K. are mainly concerned with meat production, fat lamb or beef, or with dairying. The former are most frequent in areas best suited to long-term grassland in the wetter western areas and on traditional fattening pastures. The dairying enterprises tend to be concentrated near market centres. All these intensive systems are on low ground ( < 2 0 0 m) where the climate is moist temperate, and the growing season is usually in the range 200--300 days. Typical meat-producing enterprises occur in areas where rainfall is in the range 800--1200 mm and highest mean m o n t h l y temperatures are between 15 and 18°C. The soils are dominantly brown earth with varying degrees of poor drainage, to gleys, and these were formerly associated with deciduous woodland. For many centuries these soils have been in agricultural use and many have been in permanent or semi-permanent grassland for the past 100 years. In the U.K. there are currently 2.3 X 106 and 4.9 X 106 ha of temporary and permanent grassland, respectively. N o t all of this land is devoted to the 28.5 X 106 sheep which produce 240 000 tonnes of m u t t o n and lamb annually. Some 200 000 ha are classified as mainly sheep farms b u t a further 300 000 ha are classified as cattle and sheep enterprises. The average size of a farm unit in the U.K. is 45 ha, and the average breeding flock consists of 162 sheep (Annual Review of Agriculture, 1975). To illustrate the principles involved in the operation of grassland sheep systems, data have been calculated for a hypothetical intensive lamb production system based on either pure grass (plus a large amount of fertilizer N) or mixed grass/clover (plus a small a m o u n t of fertilizer N) swards.

6.2. 4a~ Intensive sheep system using mixed pastures o f grass and clover with little use o f nitrogen fertilizer Classification. Intensive livestock system. Reference: Newbould and Floate-7; U.K. Intensive sheep farming on grass and clover, Table 12. Assumptions used to calculate nutrient balances: (1) Stocking rate, 7.25 ewes ha-'. (2) Weaning percentage, 160%. (3) 120 kg ha- 1 nitrogen fertilizer used each year. (4) All lambs sold at 45 kg live weight. (5) Bought-in replacement y o u n g stock contain equivalent amounts of nutrients to the cast ewes and deaths. (6) The approximate timetable of the system is shown in Table 11.

54

T A B L E ii

Management of stock in an intensive sheep system Time

Production period

Fields Grazing

JanumT--April

Pregnancy

April April--July

Lambing Lactation

May--June July--August

September

E w e recovery L a m b growth L a m b finishing

October November November--December

Lambs sold Mating Early pregnancy

House Conservation

Unused

Breeding sheep Silage and prelambing concentrates fed to stock

Unused Grazing Rest Silage made Silage made Grazing Rest Grazing (ewes)

Grazing (lambs) + concentrates

Grazing Unused

Breeding sheep Silage fed to stoc]

6.2.4b. Intensive sheep system using pure grass swards with heavy applications of nitrogen fertilizer Classification. Intensive livestock system. Reference: Newbould and Floate-8; U.K. Intensive sheep farming on grass only, Table 13. Assumptions used to calculate nutrient balances: (1) Stocking rate, 12 ewes ha -1. (2) Weaning percentage, 160%. (3) 300 kg ha -~ nitrogen fertilizer used each year. (4) All lambs sold at 40 kg live weight. (5) BoughtAn replacement young stock contain equivalent amounts of nutrients to the cast ewes and deaths. (6) The timetable of the system is shown in Table 11.

6. 2. 5. Systems with intensive arable f a r m i n g - winter wheat continuously Classification. Intensive arable farming. Reference: Newbould and Floate-9, Winter wheat, U.K., Table 14. About one-third of the U.K. cereal crop and nearly one-half of the wheat crop is grown in eastern England; 3.7 × 104 ha are devoted to cereal

55 production in the U.K. and of this total, 1.2 X 106 ha give an average yield of 7360 kg ha -1. Although the average farm size in the U.K. is only 45 ha, many cereal-producing farms are larger than this overall average. The annual average rainfall is less than 650 mm, of which one-half falls in the summer months (April--September, inclusive). The yields of wheat in eastern England tend, on average, to vary inversely with the total rainfall from June to August. The softs in this area are extremely variable, ranging from the Fen peat, to silts, breckland, and to heavy stiff clays. In the absence of complete data from one environment, the principles of mineral nutrient cycling in such a system are illustrated by the growing of winter wheat in monoculture using the national averages for yield of grain and quantities of fertilizer used.

Timetable for system Sow in O c t o b e r / N o v e m b e r adding a small part of the nitrogen fertilizer and most or all of the P and K; roll and top dress with furt.her nitrogen in the spring; harvest in August; burn stubble and prepare seed bed using minimum cultivation or direct drilling. 6.2.6. Nutrient balances in contrasted U.K. systems In all our systems we have assumed that plant and animal compartments (pools) are in a steady state, and we have used this assumption to calculate one closing (or balancing) entry in each section. It has been further assumed that both the total soil c o m p a r t m e n t and its constituent pools (A, B, C) are n o t necessarily in a steady state, and gains or losses have been calculated from the available d a t a These are at best only rough estimates because they represent the accumulated errors arising from assumptions and calculations made in deriving values for all the fluxes. Where u n k n o w n (pm) quantities are i n v o l v e d - particularly regarding mineralization immobilization of organic matter, and weathering fixation by soil minerals -- the calculated gains or losses are particularly doubtful. Bearing these qualifications in mind, we have attempted to draw some conclusions regarding the possible changes in the soil pools of the systems we have described.

High elevation moorland The total soft c o m p o n e n t appears to be close to steady state with respect to N and P, and the apparent loss of K m a y be made good by the release from weathering. The soil organic pool appears to be gaining N, P and K at the .expense of the available soil nutrient pool. While the steady accumulation of organic matter in litter layers and peat in such soils is possible, it cannot proceed indefinitely. It is probable that net mineralization is greater than indicated in

56

T A B L E 12 System type: Intensive livestock

Summary of . nutrient flows (units: kg ha -I y-i )

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref. n o . N e w b o u l d a n d F l o a t e - 7

U.K. Intensive sheep farming on grass a n d c l o v e r

Nutrient

N

P

K

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES :

29. 30t. 30r.

31. REMOVALS:

3. 4.

18. 26. 27.

Input by Transfer Transfer Input by

seeds or seedlings ............... by net uptake from soil ........... by net uptake from soil ........... uptake from atmosphere .......... TOTAL

-184 + --184

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by plant production remaining on feld . Transfer by seed for sowing .............. TOTAL

56 + 98 + 50) -184

SUPPLIES-REMOVALS

(0)

-20.1 --20.1

-144 + --144

6.4 + 10.8 +

45 + 77 + -(22) -144

~.9) -20.1 (0)

(0)

Changes in a m o u n t o f a n i m a l c o m p o n e n t SUPPLIES:

1. 2. 3. 4.

REMOVALS:

5. 6. 7. 8. 9.

Input by Input by Transfer Transfer

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

. . .

Output by animal products ............... O u t p u t b y losses f r o m m a n u r e t o air, b e f o r e application ......................... Output by manure .................... Transfer by application of manure and/or waste . Transfer by d r o p p i n g s on grazed areas . . . . . . . TOTAL

16 +

2.9 +

5+

56 + 98 + 170

6.4 + 10.8 + 20.1

45 + 77 + 127

17 +

3.4 +

1+

12" -52 + 89 + 170

--6.2 + 10.5 + 20.1

--46 + 80 + 127

SUPPLIES-REMOVALS

(0)

(0)

(0)

Changes in a m o u n t o f t o t a l soil c o m p o n e n t SUPPLIES:

REMOVALS:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . by d r o p p i n g s on grazed areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . by seed for sowing .............. TOTAL

19. 20. 21. 22. 23. 28. 30.

Output by denitrification ................ Output by volatilization of ammonia Output by leaching ............ iiiiiiii Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off Transfer by net uptake from soil by plant ..... TOTAL SUPPLIES-REMOVALS

52 + 89 + -120" 150 + --17" 30 + -458 pm Pm30* ---

. .

6.2 + 10.5 + -30* ---0.3*

2.9 + -49.9

22 + -191

---0"

--

---

---144 + 145

--

--

184 + 214

20.1 + 20.1

(+244)

46 + 80 + -40* ---- 3*

(+29.8)

1"

(+ 4 6 )

57

T A B L E 12 ( c o n t i n u e d ) S y s t e m t y p e : I n t e n s i v e livestock

S u m m a r y of n u t r i e n t flows (units: kg h a - I y - i )

fType o f f a r m or e c o s y s t e m o r t y p e o f p a r t o f a a r m o r e c o s y s t e m , ref. no. N e w b o u l d and Floate-7

U.K. Intensive s h e e p f a r m i n g on grass a n d clover

Nutrient

N

P

K

Changes in a m o u n t o f available soil n u t r i e n t s SUPPLIES:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

R E M O V A L S : 19. 20. 21. 22. 23. 24. 25. 30t. 30r.

Transfer by application of m a n u r e and/or waste . ~ T r a n s f e r b y d r o p p i n g s on grazed areas . . . . . . . J I n p u t b y application o f m a n u r e . . . . . . . . . . . . I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . I n p u t b y N-fixation . . . . . . . . . . . . . . . . . . . . I n p u t b y application o f litter, sludge a n d w a s t e . I n p u t b y irrigation a n d flooding . . . . . . . . . . . I n p u t b y d r y and w e t d e p o s i t i o n . . . . . . . . . . . T r a n s f e r b y w e a t h e r i n g o f soil m i n e r a l f r a c t i o n . . T r a n s f e r b y m i n e r a l i z a t i o n o f soil organic f r a c t i o n T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g o n field . T r a n s f e r b y seed f o r s o w ~ F . ~ ............ Output by denitrification . . . . . . . . . . . . . . . . O u t p u t b y volatilization o f a m m o n i a O u t p u t b y leaching . . . . . . . . . . . . i iiii~i~ O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . O u t p u t b y dust . . . . . . . . . . . . . . . . . . . . . . T r a n s f e r b y fixation in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y i t n m o b i l i z a t i o n in soil organic fraction Transfer by net uptake by the plant . . . . . . . . . Transfer by net uptake by the plant . . . . . . . . . TOTAL SUPPLIES-REMOVALS

92 + -120" 150 + --

0.8 +

107 +

17"

30* ---0.3*

40*

69 + 0

Pm7.6+ 0

--

448

387

2O8

pm

---

---

---

--

Pm30* --

22 +

0*

m P184 + -214

--21.3" m P20.1 + -41.4

+234

- 2.7

3* 36 +

1"

-18" 144 + -163 +

45

Changes in a m o u n t o f soil organic m a t t e r SUPPLIES:

8b. 9b. 10b. 13b. 25. 26b.

R E M O V A L S : 17. 28.

Transfer by application and/or waste . . . . . . . . ) 49 + T r a n s f e r b y d r o p p i n g s on grazed areas . . . . . . . Input by application of manure . . . . . . . . . . . . -I n p u t b y a p p l i c a t i o n o f litter, sludge and w a s t e . T r a n s f e r b y i m m o b i l i z a t i o n in soil organic f r a c t i o n T r a n s f e r b y p l a n t p r o d u c t s r e m a i n i n g on field . . P 3 n 0 + TOTAL 79 T r a n s f e r b y m i n e r a l i z a t i o n o f soil organic fraction O u t p u t b y organic m a t t e r , r e m o v e d b y r u n - o f f . . TOTAL SUPPLIES-REMOVALS

15.9 + ---

19 + ---

Pro2.9+ 18.8

69 + -69

--

7.6 +

+10

+11.2

---

21.3 pm

7.6

0+ 19 ---+

19

Changes in a m o u n t o f soil m i n e r a l s SUPPLY: REMOVAL:

24. 16.

T r a n s f e r b y fixation in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y w e a t h e r i n g o f soil fraction . . . . . . . SUPPLY-REMOVAL

(21.3)

18 36 (-

18)

58

T A B L E 13 S y s t e m t y p e : Intensive livestock

S u m m a r y of n u t r i e n t flows (units: kg ha -1 y - ' )

Type of farm or ecosystem or type of part of a f a r m or e c o s y s t e m , ref. no. N e w b o u l d a n d Floate-8

Intensive s h e e p f a r m i n g o n grass o n l y , U.K.

Nutrient

N

P

K

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

29. 30t.

30r.

31. REMOVALS:

3. 4. 18. 26. 27.

I n p u t b y seeds o r seedlings . . . . . . . . . . . . . . . _. T r a n s f e r by n e t u p t a k e f r o m soil . . . . . . . . . . . 200 + T r a n s f e r b y n e t u p t a k e f r o m soil . . . . . . . . . . Input by uptake from atmosphere . . . . . . . . . TOTAL 200 T r a n s f e r by c o n s u m p t i o n o f h a r v e s t e d crops . . . T r a n s f e r b y grazing o f forage . . . . . . . . . . . . . Output by primary products . . . . . . . . . . . . . . . T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g on field . TranSfer b y seed for s o w i n g . . . . . . . . . . . . . . TOTAL

_ 30.4 + . . . . . . 30.4

74 + 107 + (19) -200

SUPPLIES-REMOVALS

_ 219 +

. .

219

12.6: 16.3

72 + 118 +

-(1.5) -30.4

(0)

"(29) -219

(0)

(0)

Changes in a m o u n t o f a n i m a l c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4.

Input by Input by Transfer Transfer

5. 6.

Output by animal products . . . . . . . . . . . . . . . O u t p u t b y losses f r o m m a n u r e t o air, b e f o r e application . . . . . . . . . . . . . . . . . . . . . . . . . Output by manure . . . . . . . . . . . . . . . . . . . . Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s on grazed areas . . . . . . . TOTAL

7. 8. 9.

feed f o r livestock . . . . . . . . . . . . . . . litter used i n d o o r s . . . . . . . . by consumption of harvested crops . . . b y grazing o f forage . . . . . . . . . . . . . TOTAL

.

26 + . . . 74 + 107 + 207 +

.

4.8 + . . . 12.6 + 16.3 + 33.7

26 + 14" 0 62 + 105 + 207

SUPPLIES-REMOVALS

(0)

9+ . 72 .+ 118 + 199

5.0 + -0 11.0 + 17.7 + 33.7

2+ -0+ 73 124 + 199

(0)

(0)

Changes in a m o u n t o f t o t a l soil c o m p o n e n t SUPPLIES:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

R E M O V A L S : 19. 20. 21. 22. 23. 28. 30.

Transfer by application of manure and/or waste . • T r a n s f e r by d r o p p i n g s on grazed areas . . . . . . . Input by application of manure . . . . . . . . . . . . I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . I n p u t b y N-fixation . . . . . . . . . . . . . . . . . . . . I n p u t b y application o f litter sludge and w a s t e . I n p u t b y irrigation and flooding . . . . . . . . . . . I n p u t b y d r y and w e t d e p o s i t i o n . . . . . . . . . . . . T r a n s f e r b y p l a n t p r o d u c t s r e m a i n i n g on field . . T r a n s f e r b y seed for s o w i n g . . . . . . . . . . . . . . TOTAL

62 + 105 + -300* 10 + --

11.0 + 17.7 + -50* ---

17" (19)

0.3* (1.5)

(29)

513

80.5

309

O u t p u t b y denitrification . . . . . . . . . . . . . . . . O u t p u t by volatilization o f a m m o n i a . . . . . . . . O u t p u t b y leaching . . . . . . . . . . . . . . . . . . . . O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . O u t p u t b y dust . . . . . . . . . . . . . . . . . . . . . . O u t p u t b y organic m a t t e r , r e m o v e d b y r u n - o f f . . T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL

pm p m 5*

SUPPLIES-REMOVALS

73 + 124 + -80* -3*

-200 + 205 +308

--

-1"

--0" ---30.4 + 30.4

-219 + • 220

+50.1

+ 89

--

59

TABLE

13 (continued)

System type: Intensive livestock

S u m m a r y of nutrient flows (units: kg ha -i y-i )

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no. Newbould and Floate-8

Intensive sheep farming on grass only, U.K.

Nutrient

N

P

K

Changes in amount of available soil nutrients SUPPLIES:

REMOVALS:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

Transfer by application of manure and/or waste 104 + T r a n s f e r b y d r o p p i n g s on g r a z e d areas . . . . . . :} Input by application of manure . . . . . . . . . ... -I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . 300* Input by N-fixation .................... 10 + I n p u t by application o f litter, sludge and waste . . I n p u t by irrigation and flooding . . . . . . . . . . . . Input by dry and wet deposition ........... 17" T r a n s f e r b y w e a t h e r i n g o f soil m i n e r a l f r a c t i o n . . -T r a n s f e r b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n 69* T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g on field . 0 T r a n s f e r b y seed f o r s o w i n g . . . . . . . . . . . . . . -TOTAL 500

19. 20. 21. 22. 23. 24. 25. 30t. 30r.

Output by denitrification ................ O u t p u t by volatilization of a m m o n i a . . . . . . . . O u t p u t by leaching . . . . . . . . . . . . . . . . . . . . O u t p u t by r u n - o f f o f available n u t r i e n t s . . . . . . Output by dust ...................... T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n T r a n s f e r by n e t u p t a k e b y t h e p l a n t . . . . . . . . . T r a n s f e r by n e t u p t a k e b y t h e p l a n t TOTAL SUPPLIES-REMOVALS

1.4 + -50* -.

.

167 + -80*

0.3*

3* 36 ~

Pro7.6* 0 -59.3

29* -315

pm p m 5*

--

--

--

--

--

35.5" P~m^.4+~u

--37*

Pm^0+zu -205

-65.9

219 + -257

+295

-

+ 58

0*

6.6

1"

C h a n g e s in a m o u n t o f soil o r g a n i c m a t t e r SUPPLIES:

REMOVALS:

8b. 9b. 10b. 13b. 25. 26b.

Transfer Transfer I n p u t by Input by Transfer Transfer

by application and/or waste ........ ~ 63 + b y d r o p p i n g s on g r a z e d areas . . . . . . . application of manure ............ -a p p l i c a t i o n o f litter, sludge a n d w a s t e . -b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n b y p l a n t p r o d u c t s r e m a i n i n g on field . . PZ9 + TOTAL 82

17. 28.

T r a n s f e r b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n O u t p u t b y o r g a n i c m a t t e r , r e m o v e d by r u n - o f f . . TOTAL SUPPLIES-REMOVALS

27.3 + --Pml.5 + 28.8

69 + --

30 + ---

7.6 +

0+ 30 --

-69

7.6

0

+ 13

+21.2

+ 30

---

35.5 + pm

C h a n g e s in a m o u n t o f soil m i n e r a l s SUPPLY: REMOVAL:

24. 16.

T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y w e a t h e r i n g o f soil f r a c t i o n . . . . . . . SUPPLY-REMOVAL

+35.5

37 + 36 +

1

60

T A B L E 14 System type: Intensive arable

S u m m a r y of' n u t r i e n t f l o w s ( u n i t s : k g h a -~ y - i )

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no. Newbould and Floate-9

Winter wheat, U.K.

Nutrient

N

P

K

C h a n g e s in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

REMOVALS:

29. 30t. 30r. 31.

Input by Transfer Transfer Input by

seeds or seedlings ............... b y n e t u p t a k e f r o m soil . . . . . . . . . . . by net uptake from soil ........... uptake from atmosphere .......... TOTAL

-(95) -0 95

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by plant production remaining on field . T r a n s f e r b y seed, f o r s o w i n g . . . . . . . . . . . . . . TOTAL

--77 + 18 + -95

SUPPLIES-REMOVALS C h a n g e s in a m o u n t SUPPLIES:

REMOVALS:

(21.2) -0 21.2

(147) -0 147

--16.8 + 44 + -21.2

---

0

-147

0

0

of animal component

1. 2. 3. 4.

Input by Input by Transfer Transfer

5. 6.

Output by animal products ............... O u t j ~ u t b y l o s s e s f r o m m a n u r e t o air, b e f o r e application . . . . . . . . . . . . . . . . . . . . . . . . . . . Output by manure .................... Transfer by application of manure and/or waste . Transfer by droppings on grazed areas ....... TOTAL

7. 8. 9.

64 + 83 +

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

. . .

SUPPLIES-REMOVALS C h a n g e s in a m o u n t SUPPLIES:

REMOVALS:

o f t o t a l soil c o m p o n e n t

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

19. 20.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off . . Transfer by net uptake from soil by plant ..... TOTAL

21.

22. 23. 28. 30.

by application of manure and/or waste by droppings on grazed areas . . . application of manure . . . . . . fertilizers .................... N-fixation .................... application of litter, sludge and waste irrigation and flooding . . . . . . . . . . dry and wet deposition ........... by plant products remaining on field . by seed for sowing .............. TOTAL

SUPPLIES-REMOVALS

. . . . . . .

. .

. . . . . . . 98* 5+ . .

17" 18 + -138 m P18 + 10 + ---95 + 123 + 15

. .

. . . . . . 25.0* _ .

42*

--0.3*

--

4.4 + -29.7

83 + -128

3*

---

--

0.5 + ---21.2 + 21.7 + 8.0

16 + ---147 + 163 -

35

61

T A B L E 14 ( c o n t i n u e d ) S y s t e m t y p e : I n t e n s i v e arable

S u m m a r y of n u t r i e n t flows (units: kg h a -1 y - i )

T y p e o f f a r m or e c o s y s t e m or t y p e o f Dart o f a f a r m o r e c o s y s t e m , ref. no. N e w b o u l d a n d Floate-9

Winter w h e a t , U.K.

Nutrient

N

P

K

--

---

98 + 5+ --17" -83* --

25.0 + ---

Changes in a m o u n t o f available soil n u t r i e n t s SUPPLIES:

8a. T r a n s f e r b y applidation o f m a n u r e a n d / o r w a s t e . 9a. T r a n s f e r b y d r o p p i n g s o n grazed areas . . . . . . . 10a. I n p u t b y a p p l i c a t i o n o f m a n u r e . . . . . . . . . . . . 11. I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . 12. I n p u t b y N-fixation . . . . . . . . . . . . . . . . . . . . 13a. I n p u t b y a p p l i c a t i o n o f litter, sludge a n d w a s t e . 14. I n p u t b y irrigation and flooding . . . . . . . . . . . 15. I n p u t b y d r y and w e t d e p o s i t i o n . . . . . . . . . . . 16. T r a n s f e r b y w e a t h e r i n g o f soil m i n e r a l f r a c t i o n . . 17. T r a n s f e r b y m i n e r a l i z a t i o n o f soil organic f r a c t i o n 26a. T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g o n field . 27. T r a n s f e r b y seed for s o v o ? g ~ L . . . . . . . . . . . .

R E M O V A L S : 19. 20. 21. 22. 23. 24. 25. 30t. 30r.

42 + ---3*

0.3* P~n2.7* --

33* -83 +

38"0

Output by denitrification . . . . . . . . . . . . . . . . prn~ O u t p u t b y volatilization o f a m m o n i a . . . . . . . . 18, O u t p u t b y leaching . . . . . . . . . . . . . . . . . . . . O u t p u t by r u n - o f f o f available n u t r i e n t s . . . . . . 0 O u t p u t b y dust . . . . . . . . . . . . . . . . . . . . . . -T r a n s f e r b y fixation in soil m i n e r a l fraction . . . . -T r a n s f e r b y i m m o b i l i z a t i o n in soil organic fraction 83* T r a n s f e r b y n e t u p t a k e b y the p l a n t . . . . . . . . . 95 + Transfer by net uptake ~VOt~Elant . . . . . . . . . SUPPLIES-REMOVAI~

--

- 3

---

-0.5* 0

16" 0

17.8: 12.7 21.2 +

19" -147 +

52.2

182

-14.2

-21

, ---12.7"

--

Changes in a m o u n t o f soil organic m a t t e r SUPPLIES:

8b. 9b. 10b. 13b. 25. 26b.

R E M O V A L S : 17. 28.

T r a n s f e r b y a p p l i c a t i o n a n d / o r waste . . . . . . . . T r a n s f e r b y d r o p p i n g s o n grazed areas . . . . . . . Input by application of m a n u r e . . . . . . . . . . . . I n p u t b y a p p l i c a t i o n o f litter, sludge and w a s t e . T r a n s f e r b y i m m o b i l i z a t i o n in soil organic fraction T r a n s f e r b y p l a n t p r o d u c t s r e m a i n i n g on field . . TOTAL

83* 18 + 101

T r a n s f e r b y m i n e r a l i z a t i o n o f soil organic f r a c t i o n O u t p u t by organic m a t t e r , r e m o v e d b y r u n - o f f . . TOTAL

83* 0 83

SUPPLIES-REMOVALS

--

4.4 +

---

0

17.1

0

12.7" 0 12.7

0 0 0

+18

+ 4.4

---

17.8" pm

0

Changes in a m o u n t o f soil minerals SUPPLY: REMOVAL:

24. 16.

T r a n s f e r b y fixation in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y w e a t h e r i n g o f soil f r a c t i o n . . . . . . . SUPPLY-REMOVAL

+17.8

19" 33 -14

62

NOTES TO TABLE 12. (Reference Newbould and Floate-7) 1. It is assumed that 'finishing' lambs are fed 0.45 kg concentrate feed per day for 21 days and that each pregnant ewe eats 51 kg y-I of the same feed; the concentration of nutrients in the feed was taken to be 3.3% N, 0.16% P and 1.1% K. 4. Herbage production, 5750 kg of dry matter per ha (4250 without fertilizer, plus 120 × 12.5 = 1500 following the application of nitrogen fertilizer). It is assumed that 15% dry matter is wasted or spoiled in the grazing process and that 25% dry matter is wasted in making and feeding silage. On these assumptions the overall utilisation of available herbage was taken to be 81%. The concentration of nutrients in grass/clover silage was taken to be 3.5% N, 0.4% P, 2.8% K, and in the freshly grazed grass/clover 3.2% N, 0.35% P and 2.5% K (Spedding and Diekmahns, 1972). 5. The system on this pasture type is operated to the schedule described previously (Table 11). It was assumed that the lambs were sold weighing 45 kg each, and that the nutrients in the bought-in replacement hoggs balance those in the sold-off cast ewes. The concentrations of nutrients in the lamb carcass were taken as 2.8% N, 0.65% P and 0.18% K (Sykes and Field, 1972). It is assumed that each ewe produces 2 kg wool containing 17.8% N (Ryder and Stephenson, 1968). 8, 9. The nutrients are apportioned between faeces and urine in the same manner as that described in ref. Newbould and Floate-2 to -5. 11. Fertilizer amounts are based on national average levels (Church, 1975) and on recommendations of the Edinburgh School of Agriculture (1969). 12. Nitrogen fixed by clover in the U.K. is reported to vary from 23 to 400 kg ha -1 by Nutman (1971) and from 105 to 430 kg ha -~ by Whitehead (1970). An approximate mean value of 150 kg ha -~ was used. 15. Inputs in rain are based on Cooke (1976). 16, 17. The net quantities of K released by weathering, and of nitrogen and P mineralized from organic matter are based on uptake by unfertilized leys on the reference plots at Rothamsted (Widdowson and Penny, 1973). 21. Leaching loss for nitrogen is based on Low (1973), for P and K on Cooke (1976). Use of the latter data may underestimate K loss; Wilkinson and Lowrey (1973) quote values up to 139 kg ha -1. 24. 71% of P and 46% of K in applied fertilizer is assumed to add to the mineral soil fraction (Widdowson and Penny, 1973). 25. System is assumed to be gaining in organic matter and hence N and P, but amounts immobilised by the soil organic fraction are not known. 26a. It is assumed that all K enters the pool of available soil nutrients. 26b. It is assumed that N and P remain in the soil organic matter pool. NOTES TO TABLE 13. (Reference Newbould and Floate-8) Entries identical to those for Table 12, except for the following: 4. Herbage production, 9500 kg dry matter per ha (2000 without fertilizer, plus 300 × 25 = 7500 in response to nitrogen fertilizer). On the same assumptions of wastage in grazing and making silage as were used in the previous system, the overall utilisation of available herbage was taken to be 81%. Nutrients in grass silage are assumed to be 2.8% N, 0.48% P and 2.7% K (Lush, 1952), those in grazed grass are 2.1% N, 0.32% P and 2.31% K (Whitehead, 1966). 5. It is assumed that all lambs are sold at 40 kg each and that nutrients in the bought-in replacement hoggs balance those in the sold-off cast ewes.

63

12. Nitrogen fixed in soils under fertilized grassland is estimated at 10 kg ha-~ (Jenkinson, unpublished data, 1975).

N O T E S T O T A B L E 14. (Reference Newbould and Floate-9) 11. Fertilizer amounts are national average levels used on winter wheat (Church, 1975). At Rothamsted, from which other data for the balance on this crop were obtained, the amounts of fertilizerN, P and K used annually on arable crops, including winter wheat, over a period of 15 years were, on average, 70--118 N, 27 P and 104--208 K (kg ha -~) (Widdowson and Penny, 1973). The N and P levels used at Rothamsted are similar to the national averages but the amount of K is very m u c h greater. 12. Nitrogen fixation estimated (Jenkinson, unpublished data, 1975). 15. Average nutrients in rain at Rothamsted, Woburn and S a x m u n d h a m 1969--1973 (Cooke, 1976). For Rothamsted, Williams (1976) gives 17.5 N, 0.81 P and 4.5 K (kg ha -I). 16, 17. The net quantities of potassium released by weathering and of nitrogen and phosphate mineralized from organic matter were based on the average uptake by unfertilized wheat over a period of 15 years (Widdowson and Penny, 1973) (see also 25). 18. The yield of grain was taken as 4356 kg ha -~, i.e.the average yield for the U.K. crop in 1973/1974 (Annual Review of Agriculture, 1975). The contents of nutrients used for wheat grain were 1.8% N, 0.4% P, 1.5% K, and for straw were 0.42% N, 0.1% P, 1.9% K (Halliday, 1948). 20. Yield of straw was assumed to be similar to the yield of grain and it was assumed that straw was burnt in situ, resulting mainly in a loss of nitrogen. 21. Leaching losses based on mean data for Rothamsted 1970--1974. Ranges N (3.85-82.3), P ( 1 year = 2.800 kg s.e. Before 1940 the net production of grassland in the absence of fertilizers was 2200 kg s.e. The milk production at that time was 3400 kg with a fat c o n t e n t of 3.2%. Each cow (500 kg) was accompanied by 0.39 calf aged 3--6 m o n t h s and 0.32 calf > 1 year. This leads to an annual requirement per cow plus accompanying y o u n g animals of 2546 kg s.e. Thus, farms in the thirties could afford a cattle density of 0.86 dairy cow per ha together with accompanying y o u n g cattle. This cattle density is in agreement with that at the beginning of this century in The Netherlands (De Boer, 1975). Nowadays there may still be areas where no fertilizers are used. Nevertheless, the farmer will like a higher production. This higher production can only be attained by using concentrates. Tables 23 and 24 show the nutrient balances of both farm types. In the seventies the production of the milking cows is 4500 kg milk with 4% fat. The weight of a cow is 550 kg. Each cow is accompanied by 0.41 calf age < 1 year and 0.44 calf > 1 year. Using 400 kg N as fertilizer the net production is 4500 kg s.e. (Anonymus, 1975). This leads to an annual requirem e n t per cow plus accompanying y o u n g animals of 3272 kg s.e., which means that a cattle density of 1.37 cow per ha, together with accompanying y o u n g cattle is possible. Of course, higher densities are achieved by using concentrates. Tables 25 and 26 show the nutrient balances of two farms using 400 kg N ha -~ y-~; one with a density of 2.5 cows + accompanying y o u n g cattle, the other with a density of 4 cows + accompanying y o u n g cattle. For the farm with 2.5 cows per ha on marine clay soil the m e t h o d of calculation is given. Some remarks should be made about the other calculations. (1) On the farm w i t h o u t fertilizers the net production (= food value taken up by the animals) will, because of lower cattle density, be higher than on intensive farms. For Tables 23 and 24 we assumed a utilization of 70% of the grass production. For Tables 25 and 26 we assumed a utilization of 60% of the grass production.

82

T A B L E 23 System type: Extensive livestock

Summary of nutrient flows (units: kg ha -I y-1 )

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no. Henkens-1

D u t c h d a i r y f a r m , c l a y soil, 1 9 3 7 ; 0 . 8 6 " c o w s h a - ~ , n o = fertilizers, no supplemental feed, milk production 2 9 2 4 1 h a - I , m e a t 1 4 5 k g h a -I

Nutrient C h a n g e s in a m o u n t SUPPLIES:

REMOVALS:

29. 30t. 30r. 31. 3.

4. 18. 26. 27.

N

P

K

-158 + pm -158

-23 + pm -23

-158 + pm -158

50 + 61 + -47 + -158

7+ 9+ 7+

50 + 61 + -47 + -158

of plant component Input by Transfer Transfer Input by

seeds or seedlings ............... by net uptake from soil ........... b y n e t u p t a k e f r o m soil . . . . . . . . . . . uptake from atmosphere .......... TOTAL

Transfer by consumption of harvested crops . . Transfer by grazing of forage ............ : Output by primary products .............. Transfer by plant production remaining on field . Transfer by seed for sowing .............. TOTAL SUPPLIES-REMOVALS

-23

0

0

0

--50 + 61 + 111

-7+ 9+

-50 +

16

61 + 111

19: 34+ _ 37:

4+ -Z 5+

5+ -_ 48 +

46 109

16

58 + 111

+ 2

0

0

37 + 46 + -0 120 + --

5+ 7+ -0 ---

14" 47 -264

1" 7 -20

48 + 58 + -0 ---5* 47 -158

49 + 7T 11 + 0 0 150+8 225

--0 0 0 0 23 23

5 0 0 0 158 163

39

-3

-

C h a n g e s in a m o u n t o f a n i m a l c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4. 5. 6. 7. 8. 9.

Input by Input by Transfer Transfer

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by gra~ing of forage ............. TOTAL

. . .

Output by animal products ............... Outl}ut by losses from manure to air, before 6d application ...................... 6m Output by manure .................... Transfer by application of manure and/or waste . Transfer by droppings ongrazed areas ....... TOTAL SUPPLIES-REMOVALS

C h a n g e s in a m o u n t SUPPLIES:

REMOVALS:

o f t o t a l soil c o m p o n e n t

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . by droppings on grazed areas ....... application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . by seed for sowing .............. TOTAL

19. 20. 21. 22. 23. 28. 30.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off.. T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL SUPPLIES-REMOVALS

--

5

83

T A B L E 23 ( c o n t i n u e d ) System type: Extensive livestock

Summary of n u t r i e n t flows ( u n i t s : k g ha -1 y - t )

Type of farm or ecosystem or type of part of a f a r m or e c o s y s t e m , ref. n o . H e n k e n s - 1

D u t c h d a i r y f a r m , clay soil, 1 9 3 7 ; 0.86 c o w s ha-t~ no fertilizers, no s u p p l e m e n t a l feed, m i l k p r o d u c t i o n 2 9 2 4 l/ha, m e a t 145 k g / h a

Nutrient

N

P

K

C h a n g e s in a m o u n t o f available soil n u t r i e n t s SUPPLIES:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

T r a n s f e r by a p p l i c a t i o n o f m a n u r e a n d / o r w a s t e . T r a n s f e r b y d r o p p i n g s on g r a z e d areas . . . . . . . Input by application of manure ............ I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . Input by N-fixation .................... I n p u t b y a p p l i c a t i o n o f litter, sludge a n d w a s t e . I n p u t by irrigation and flooding . . . . . . . . . . . Input by dry and wet deposition ........... T r a n s f e r b y w e a t h e r i n g b f soil m i n e r a l f r a c t i o n . . T r a n s f e r by m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n T r a n s f e r by p l a n t p r o d u c t i o n r e m a i n i n g on field . Transfer by seed for sowing . . . . . . . . . . . . . . TOTAL

25 + 31 + -0 120 + --14" -0 32 + -222

5+ 7+ -0 ---1 0 0 7 -20

48 + 58 + -0 ---5 0 -47 -158

REMOVAI~:

19. 20. 21. 22. 23. 24. 25.

Output by denitrification ................ O u t p u t by volatilization of a m m o n i a . . . . . . . . Output by leaching .................... O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . Output by dust ...................... T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n

4 9 ++ 7 11 + 0 0 -150+8

--0 0 0 0 20+3

--

30r.

Transfer by net uptake by the plant . . . . . . . . . TOTAL

pm 225

~

~3

-

-3

-

30t.

Transfer b y net uptake b y the plant . . . . . . . . .

SUPPLIES-REMOVALS

5 0 0 0

158 ÷

3

5

C h a n g e s in a m o u n t o f soil o r g a n i c m a t t e r SUPPLIES:

8b. Transfer by application a n d / o r waste . . . . . . . . 9 b . T r a n s f e r b y d r o p p i n g s on g r a z e d areas . . . . . . .

10b. I n p u t b y a p p l i c a t i o n o f m a n u r e . . . . . . . . . . . .

13b. I n p u t b y a p p l i c a t i o n o f litter, s l u d g e a n d w a s t e . 25. T r a n s f e r b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n 2 6 b . T r a n s f e r b y p l a n t p r o d u c t s r e m a i n i n g on field . . TOTAL R E M O V A L S : 17. 28.

12 + 15 + --0 15 + 42

0+ 0+ --0 0+ 0

0 0 0

0 0 0

0 0 0

+42

0

0

T r a n s f e r b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n O u t p u t by o r g a n i c m a t t e r , r e m o v e d b y r u n - o f f . . TOTAL SUPPLIES-REMOVALS

C h a n g e s in a m o u n t o f soil m i n e r a l s SUPPLY: REMOVAL:

24. 16.

T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y w e a t h e r i n g o f soil f r a c t i o n . . . . . . . SUPPLY-REMOVAL

---

0+ 0+ ---0+ 0

84

'TABLE 24 System type: Intensive livestock

Summary of nutrient flows (units: kg ha-'

Type of farm or ecosystem or type of part of a

D u t c h d a i r y f a r m , c l a y soil, 1 9 3 7 ; 0 . 8 6 c o w s h a - ' , no fertilizers, with supplemental feed milk produc tion 3800 kg ha -I, meat 145 kg ha-'

farm or ecosystem, ref. no. Henkens-2 Nutrient C h a n g e s in a m o u n t

y-' )

N

P

K

-158 + pm -158

-23 + pm -23

-158 + pm -158

38 + 73 + -47 + -158

6+ 10 + 7 +

38 + 73 + -47 + -158

of plant component

SUPPLIES :

29. 30t. 30r. 31.

Input by Transfer Transfer Input by

seeds or seedlings ............... b y n e t u p t a k e f r o m soil . . . . . . . . . . . b y n e t u p t a k e f r o m soil . . . . . . . . . . . uptake from atmosphere .......... TOTAL

REMOVALS:

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by plant production remaining on field . Transfer by seed for sowing .............. TOTAL SUPPLIES-REMOVALS

0

-23 0

0

C h a n g e s in a m o u n t o f a n i m a l c o m p o n e n t SUPPLIES:

1.

2. 3. 4. REMOVALS:

5. 6. 7. 8. 9.

Input by Input by Transfer Transfer

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

. . .

19 + -38 + 73 + 130

4+ -6+ 1 20

8+ -38 + 73 + 119

Output by animal products ............... O u t l ? u t b y l o s s e s f r o m m a n u r e t o air, b e f o r e 6d application ....................... 6m Output by manure .................... Transfer by application of manure and/or waste . Transfer by droppings on grazed areas ....... TOTAL

24: 5+ 4 -44 + 55 + 132

5+ ---

---

8 + 7+ 20

43 + 70 + 119

0

0

SUPPLIES-REMOVALS C h a n g e s in a m o u n t SUPPLIES:

REMOVALS:

-

2

6+

o f t o t a l soil c o m p o n e n t

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . by droppings on grazed areas ....... application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . by seed for sowing .............. TOTAL

19. 20. 21. 22. 23. 28. 30.

Output by denitrificatton ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output" by dust ...................... Output by organic matter, removed by run-off . . T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL SUPPLIES-REMOVALS

44 + 55 + 0+

8+ 7+

120 + --

0 -Z

14" 47 + -280

1" 7 -23

51 + 8+ 12: 0+ 0+

-O +

43 + 70 + 0 --5* 47 -165 --

0+

5+ 0 ++

150+ 229

0+ 23 + 23

0+ 158 + 163

51

0

2

85

TABLE 24 (continued) System type: Intensive livestock

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no. Henkens-2

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -~ y - i ) D u t c h d a i r y f a r m , c l a y soil, 1 9 3 7 ; 0 . 8 6 c o w s h a -~ no fertilizers with supplemental feed, milk produ~ t i o n 3 8 0 0 k g h a - , m e a t 1 4 5 k g ha -~

Nutrient C h a n g e s in a m o u n t SUPPLIES:

REMOVALS:

by application of manure and/or waste . by droppings on grazed areas ....... application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... b y w e a t h e r i n g o f soil m i n e r a l f r a c t i o n . . b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n by plant production remaining on field . by seed for sowing .............. TOTAL

30 + 37 + -0+ 120 + --14" -0+ 32 + -233

8+ 7+ -0 ---1" 0+ 0+ 7+ -23

19. 20. 21. 22. 23. 24. 25. 30t. 30r.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Transfer by fixation in soil mineral fraction .... T r a n s f e r b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n Transfer by net uptake by the plant ......... Transfer by net uptake by the plant TOTAL

51 + 8 12 + 0 0 -0 158 + pm 229

--0 0 0 0 0 23 + pm 23

8b. 9b. 10b.

13b. 25. 26b. 17. 28.

C h a n g e s in a m o u n t 24. 16.

+ 4

0

43 + 70 + -0 ---5* _0 47 -165 -5+ 0 0 0 -158 + pm 163 + 2

o f soil o r g a n i c m a t t e r Transfer Transfer Input by Input by Transfer Transfer

by application and/or waste ........ by droppings on grazed areas ....... application of manure ............ application of litter, sludge and waste . b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n by plant products remaining on field . . TOTAL

14 + 18 + -0+ 15 + 47

SUPPLY-REMOVAL

--

--

--

-O+

--0+ 0

0 0 0

0 0 0

0 0 0

+47

0

0

of soil minerals T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y w e a t h e r i n g o f soil f r a c t i o n . . . . . . .

--

0+ 0

T r a n s f e r b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n Output by organic matter, removed by run-off . . TOTAL SUPPLIES-REMOVALS

SUPPLY: REMOVAL:

K

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer Transfer Transfer

C h a n g e s in a m o u n t

REMOVALS:

P

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

SUPPLIES-REMOVALS

SUPPLIES:

N o f a v a i l a b l e soil n u t r i e n t s

---

86

T A B L E 25 System type: Intensive livestock

Stimmary" of n u t r i e n t flows ( u n i t s : kg ha - I y - i )

T y p e o f farm or e c o s y s t e m or t y p e o f part o f a f a r m o r e c o s y s t e m , ref. n o . H e n k e n s - 3

D u t c h d a i r y f a r m , c l a y s o i l , 1 9 7 2 ; 2.5 c o w s h a -~ w i t h fertilizers, with supplemental feed, milk production 11 2 5 0 k g h a -~, m e a t 4 8 0 k g h a -~

Nutrient

N

P

K

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

29. 30t. 30r. 31.

Input by Transfer Transfer Input by

seeds or seedlings ............... b y net, u p t a k e f r o m s o i l . . . . . . . . . . . by net uptake from soil ........... uptake from atmosphere .......... TOTAL

REMOVALS:

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . T r a n s f e r b y g r a z i n g o f f o r a g e . .. . . . . . . . . . . . Output by primary products .............. Transfer by plant production remaining on field . Transfer by seed for sowing .............. TOTAL SUPPLIES-REMOVALS

-450 + pm -450

-57 + pm -57

-375 + pm -375

126 + 144 + -180 + -450

16 + 18 + -23 + -57

105 + 120 + -150 + -375

0

0

0

Changes in a m o u n t o f a n i m a l c o m p o n e n t SUPPLIES:

1. 2.

3. 4. REMOVALS:

5. 6. 7. 8. 9.

Input by Input by Transfer Transfer

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

. . .

Output by animal products ............... O u t p u t b y l o s s e s f r o m m a n u r e t o air, b e f o r e 6m application ....................... 6d Output by manure .................... Transfer by application of manure and/or waste . Transfer by d r o p p i n g s o n g r a z e d areas . . . . . . . TOTAL SUPPLIES-REMOVALS

158 + -126 + 144 + 428

37 + -16 + 18 + 71

70 + -105 + 120 + 295

72 + 13 + 16

14 + ---26 + 31 + 71

18 + ---127 + 150 + 295

0

0

-149 + 178 + 428 0

Changes in a m o u n t o f t o t a l soil c o m p o n e n t SUPPLIES:

REMOVALS:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Tr~Lnsfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . by d r o p p i n g s on grazed areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field • . by seed for sowing .............. TOTAL

19. 20.

Output by denitrification ................ Output by volatilization of ammonia .....

21. 22. 23. 28. 30.

Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off . . Transfer by net uptake from soil by plant ..... TOTAL

20m 20d

SUPPLIES-REMOVALS

149 + 178 + -400 + 0~ 14" 160 + 921 169 + 12 + 14 + 39 0 0 0 450 + 684 +237

26 + 31 + -----1" 2 -81

127 + 150 + ---5* 15 432

--

--

--

--

0* 0 0 0 57 + 57 +24

11" 0 0 0 375 + 386 +46

87

T A B L E 25 ( c o n t i n u e d ) S y s t e m t y p e : Intensive livestock

S u m m a r y of n u t r i e n t flows (units: kg h a - 1 y - i )

T y p e o f f a r m o r e c o s y s t e m or t:vpe o f p a r t o f a f a r m o r e c o s y s t e m , ref. no. Henkens-3

D u t c h dairy f a r m , clay soil, 1 9 7 2 , 2.5 Cows ha -1, with fertilizers, with s u p p l e m e n t a l feed, milk p r o d u c t i o n 11 250 kg ha -1, m e a t 480 kg h a -~ N P K

Nutrient Changes in a m o u n t o f available soil n u t r i e n t s SUPPLIES:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

T r a n s f e r b y application o f m a n u r e a n d / o r w a s t e . T r a n s f e r by d r o p p i n g s on grazed areas . . . . . . . I n p u t b y application o f m a n u r e . . . . . . . . . . . . I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . I n p u t b y N-fixation . . . . . . . . . . . . . . . . . . . . I n p u t b y application o f litter, sludge and w a s t e . I n p u t b y irrigation a n d flooding . . . . . . . . . . . I n p u t b y d r y and w e t d e p o s i t i o n . . . . . . . . . . . T r a n s f e r b y w e a t h e r i n g o f soil m i n e r a l f r a c t i o n . . T r a n s f e r b y m i n e r a l i z a t i o n o f soil organic fraction T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g on field . T r a n s f e r b y seed for sowingTOTAL ..............

766

R E M O V A L S : 19. 20. 21. 22. 23. 24. 25. 30t. 30r.

O u t p u t b y denitrification . . . . . . . . . . . . . . . . O u t p u t b y volatilization o f a m m o n i a . . . . . . . . O u t p u t b y leaching . . . . . . . . . . . . . . . . . . . . O u t p u t by r u n - o f f o f available n u t r i e n t s . . . . . . O u t p u t by dust . . . . . . . . . . . . . . . . . . . . . . T r a n s f e r by fixation in soil m i n e r a l fraction . . . . T r a n s f e r by i m m o b i l i z a t i o n in soil organic fraction Transfer by net uptake by t h e plant . . . . . . . . . T r a n s f e r b y n e t u p t a k e b y the p l a n t . . . . . . . . . TOTAL

169 + 26 + 39 + 0 0 -0 450 + pm 684

0 0 0 0 57 + pm 57

375 + pm 386

+82

+24

+46

SUPPLIES-REMOVALS

100 + 120 + -400 + 0 --14" -130+2

26 + 31 + -----

127 + 150 + -----

1" 0 20+3

--5* 0

81 ---0+

150 + 432 --11 + 0 0 0

Changes in a m o u n t o f soil organic m a t t e r SUPPLIES:

8b. 9b. 10b. 13b. 25. 26b.

R E M O V A L S : 17. 28.

Transfer Transfer Input by Input by Transfer Transfer

by application and/or waste . . . . . . . . b y d r o p p i n g s on grazed areas . . . . . . . application o f m a n u r e . . . . . . . . . . . . a p p l i c a t i o n o f litter, sludge and w a s t e . by i m m o b i l i z a t i o n in soil organic fraction by p l a n t p r o d u c t s r e m a i n i n g on field . . TOTAL

49 + 58 + --

--

--

--0 + 48 + 155

--0 + 0+ 0

--

0 0 0

0 0 0

T r a n s f e r b y m i n e r a l i z a t i o n o f soil organic fraction O u t p u t b y organic m a t t e r , r e m o v e d b y r u n - o f f . . TOTAL SUPPLIES-REMOVALS

155

Changes in a m o u n t o f soil minerals SUPPLY: REMOVAL:

24. 16.

T r a n s f e r by fixation in son m i n e r a l fraction . . . . T r a n s f e r b y w e a t h e r i n g o f soil fraction . . . . . . . SUPPLY-REMOVAL

---

0

0+

0+

0

0

0 0 0 0 0 0

88

TABLE 26 System type: Intensive livestock

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -~ y - i )

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no. Henkens-4

Dutch dairy farm on clay soil, 4 cows ha-I with fertilizers and large amount of supplemental f e e d , m i l k p r o d . 1 8 0 0 0 1 h a -~, m e a t 7 6 8 k g h a -I

Nutrient Changes in amount SUPPLIES:

29. 30t. 30r.

31. REMOVALS:

3. 4. 18. 26. 27.

N

P

K

-450 + pm -450

-57 + pm -57

-375 + pm -375

21 + 249 + -180 + -450

3+ 31 + -23 + -57

18 + 207 + -150 + -375

0

0

86 + --3+

of plant component Input by Transfer Transfer Input by

seeds or seedlings ............... b y n e t u p t a k e f r o m soil . . . . . . . . . . . b y n e t u p t a k e f r o m soil . . . . . . . . . . . uptake from atmosphere .......... TOTAL

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by plant production remaining on field . T r a n s f e r b y s e e d {~or s o w i n g . . . . . . . . . . . . . . TOTAL SUPPLIES-REMOVALS

0

C h a n g e s in a m o u n t o f a n i m a l c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4.

Input by Input by Transfer Transfer

feed for livestock ............... litter used indoors b y c o n s u m p t i o n o f t~arvestecl "crofts" ~ i i by grazing of forage ............. TOTAL

369 + -214. 249 + 639

31 + 120

164 + -18 + 207 + 389

5. 6.

Output by animal products ............... O u t p u t b y l o s s e s f r o m m a n u r e t o air, b e f o r e 6m application ....................... 6d Output by manure .................... Transfer by application of manure and/or waste . Transfer by droppings ongrazed areas ....... TOTAL

115 + 17 + 25 + -190 + 292 + 639

22 + ---48 + 50 + 120

29 + ---111 + 249 + 389

7. 8. 9.

SUPPLIES-REMOVALS C h a n g e s in a m o u n t SUPPLIES:

REMOVALS:

0

0

0

o f t o t a l soil c o m p o n e n t

8. 9. 10. 11. 12. 13. 14. 15. 26.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer

by application of manure and/or waste . by droppings on grazed areas ....... application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . .

27.

T r a n s f e r b y s e e d f o r sowingTOTAL ..............

19. 20.

Output by denitrification ................ Output by volatilization of ammonia .....

21. 22. 23. 28. 30.

Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off . . T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL

20m

48 + 50 + ---

--

----5*

1"

192 + 15 + 23 + 44 ~ 0 0 0 450 + 724 +352

111~" 249 + --

---

14" 180 + 1076

2 0 d

SuPPLIES-REMOVALS

190 + 292 + -400 + 0 --

23 + 122

150 + 515

--

--

--

--

0* 0 0 0 57 + 57 65

16" 0 0 370+5 391 124

89

T A B L E 26 ( c o n t i n u e d ) S y s t e m type: Intensive livestock

Summary of n u t r i e n t flows ( u n i t s : k g h a -1 y-~ )

T y p e o f f a r m or e c o s y s t e m o r t y p e o f p a r t o f a

D u t c h d a i r y f a r m on clay soil, 4 c o w s ha -I w i t h fertilizers a n d large a m o u n t o f s u p p l e m e n t a l feed, m i l k p r o d . 18 0 0 0 1 ha -1, m e a t 7 6 8 k g ha -t

f a r m or e c o s y s t e m , ref. no. H e n k e n s - 4 Nutrient

N

P

K

C h a n g e s in a m o u n t o f available soil n u t r i e n t s SUPPLIES:

8a. 9a. 10a. 11. 12.

13a. 14. 15. 16. 17. 26a. 27. R E M O V A L S : 19. 20. 21. 22. 23. 24. 25. 30t. 30r.

Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s on g r a z e d areas . . . . . . . Input by application of manure ............ I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . Input by N-fixation .................... I n p u t b y a p p l i c a t i o n o f litter, s l u d g e a n d w a s t e . I n p u t by irrigation and flooding . . . . . . . . . . . I n p u t by dry and wet deposition . . . . . . . . . . . T r a n s f e r b y w e a t h e r i n g o f soil m i n e r a l f r a c t i o n . . T r a n s f e r b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g on field . Transfer by seed for sowing . . . . . . . . . . . . . . TOTAL

128 + 197 + -400 + 0 --14" -0 132 + -871

Output by denitrification ................ O u t p u t by volatilization of a m m o n i a . . . . . . . . Output by leaching . . . . . . . . . . . . . . . . . . . . O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . Output by dust ............... ....... T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n Transfer by net uptake by the plant . . . . . . . . . Transfer by net uptake by the plant TOTAL

192 + 38 + 44" ---0+ 450 pm 724

SUPPLIES-REMOVALS

+147

48 + 50 + --

111 + 249 + --

--

--

----1"

----5*

0 0 23 + -122

0 150 + -515

--

-0*

--0 0 57 + pm 57 65

16" --0 375 + pm 391 124

C h a n g e s in a m o u n t o f soil o r g a n i c m a t t e r SUPPLIES:

REMOVALS:

8b. T r a n s f e r 9b. Transfer 10b. I n p u t by 13b. I n p u t b y 25. Transfer 26b. Transfer 17. 28.

by application and/or waste . . . . . . . . b y d r o p p i n g s on g r a z e d areas . . . . . . . application of manure ............ application o f litter, sludge and waste . b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n b y p l a n t p r o d u c t s r e m a i n i n g on field . . TOTAL

62 + 95 + --0 48 + 205

T r a n s f e r b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n O u t p u t b y o r g a n i c m a t t e r , r e m o v e d by r u n - o f f . . TOTAL SUPPLIES-REMOVALS

24. 16.

T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y w e a t h e r i n g o f soil f r a c t i o n . . . . . . . SUPPLY-REMOVAL

0

0

0 0 0

0

---0 0

0 0 0

0 0 0

0 0 0

205

0

0

C h a n g e s in a m o u n t o f soil m i n e r a l s SUPPLY: REMOVAL:

0 ---

---

90

NOTES TO TABLES 23--26 (References Henkens-1 to -4) 30t. Nutrient flow on a farm with 2.5 cows + accompanying young animals (Table 25). Milk production per cow 4500 kg ~ per ha 11250 kg Meat production per cow 192 kg -~ per ha 480 kg Annual requirement per cow 3272 kg s.e. -, 2.5 cow = 8180 kg s.e. Net production of grassland 4500 kg s.e. " ffi 9000 kg d.m. Efficiency 60% -, Total gross production (10/6) × 9000 = 15000 kg d.m. containing 3% N; 0.38% P; 2.5% K. Thus: Nutrient uptake from soil: 450 kg N; 57 kg P; 375 kg K and 26. Remaining on the field, 40%: 180 kg N; 23 kg P; 150 kg K 3. Winter production, 45% -* requirement 3681 kg s.e. Harvested 1.2 cuttings ha -1 = 1.2 × 1750 2100 kg s.e. Needed from concentrates during winter = 1581 kg s.e. = 2433 kg of concentrates (Cw). Thus: Harvested for winter feeding, 2100 kg s.e. = 4200 kg d.m. (3% N; 0.38% P; 2.5% K), i.e. Harvested on farm: 126 kg N; 16 kg P; 105 kg K 4. Left for grazing, 4500--2100 = 2400 kg s.e. = 4800 kg d.m. Thus: Taken up by grazing: 144 kg N; 18 kg P; 120 kg K 5. Milk contains 0.53% N; 0.09% P; 0.15% K (Anonymus, 1961, 1967). Meat contains 2.60% N; 0.74% P; 0.19% K Animal products sold: 11250 kg milk -, 59.6 kg N; 10.1 kg P; 16.9 kg K 480 kg m e a t - , 1 2 . 5 kg N; 3 . 6 k g P ; 0 . 9 k g K Total animal products sold: 72 kg N; 14 kg P; 18 kg K 1. Summer production, 55% -, requirement 4499 kg s.e. Uptake by grazing 2400 kg s.e. Needed from concentrates during summer 2099 kg s.e. = 3229 kg of concentrates (Cs). Thus: Total concentrates C w + C s = 1581 + 2099 = 3680 kg s.e. = 5662 kg of concentrates Nutrient content of concentrates: 2.79% N; 0.65% P; 1.24% K. Thus, Concentrates: 158 kg N; 37 kg P; 70 kg K 6m. Manure production in winter Uptake from harvested crop 126 kg N; 16 kg P; 105 kg K Uptake from concentrates (Cw) 68 kg N; 16 kg P; 30 kg K Total uptake during winter In meat and milk (45% X i t e m 5 )

194 kg N; 32 kg P; 135 kg K 32kgN; 6kgP; 8kgK

In manure 162 kg N; 26 kg P; 127 kg K Part of the nitrogen in manure is mineral; part is organic. Part of the organic nitrogen is available after a short time (Nf); part becomes available later (Nr) -, soil organic matter. Thus, N t = N m + N f + N r Nm= 0.4 Nt; Nf = 0.3 Nt; N r = 0.3 N t (Anonymus, 1976) Part o f the N m will be lost to the air before it reaches the soil. This is + 20%. Thus, Lost from manure to air: 0.2 x 0.4 N t = 0.08 N t = 13 kg N 8a. The rest of the N m will be available, whereas the Nf will become available during the year; the N r will become available in the following years. Thus, Manure from own farm: 0.8 N m + Nf = 0.32 N t + 0.3 N t = 100 kg N; 26 kg P; 127 kg K 8b. Manure from own farm: N r = 0.3 N t = 49 kg N 8. Manure applied to own farm: 8a + 8b = 149 kg N; 26 kg P; 127 kg K 6d. Droppings on grazed areas Uptake by grazing 144 kg N; 18 kg P; 120 kg K Uptake from concentrates (Cs) 90 kg N; 21 kg P; 40 kg K

91

Total uptake during summer In meat and milk (55%x i t e m 5 )

234 kg N; 39 kg P; 160 kg K 40kgN; 8kgP; 10kgK

In droppings 194 kg N; 31 kg P; 150 kg K Before the droppings reach the soil ± 20% of N m will be lost to the air. Thus, Lost from droppings to air: 0.2 × 0.4 N t = 0.08 N t = 16 kg N 9b. Droppings on grazed area: N r = 0.3 N t = 58 kg N 9a. Droppings on grazed area: 0.8 N m + Nf -- 0.32 N t + 0.3 N t = 120 kg N; 31 kg P; 150 kg K 9. Droppings on grazed area: 9a + 9b = 178 kg N; 31 kg P; 150 kg K 20. On grassland, manure and droppings are not ploughed in. Lying on top of the soil ± 20% of the N m from items 8 and 9 will be lost by volatilization. Thus, Volatilization: from manure (20m) = 0.2 N m ~- 0.08 N t (item 8) -- 12 kg N from droppings (20d) ~- 0.08 N t (item 9) -- 14 kg N Total 26 kg N 11. Based on Anonymus, 1976, the net s.e. production of 4500 kg ha -1 can be achieved by fertilizing with 400 k g N per ha. Fertilizing with P and K is not needed, keeping the mentioned number of animals. Thus, Fertilizers: 400 kg N; 0 kg P; 0 kg K 12. At this nitrogen level N-fixation is negligible. 15. Between 1 October 1973 and 1 October 1974 the rain was collected in 14 different places scattered over the country, and was analysed for N.P.K. (Henkens, 1976). Rain: 14kgN; 1.0kgP; 5kgK 21. Henkens (1972, 1976) mentions some analytical data for drainage water on grassland, thus: Leaching: 39 kg N; 0.24 kg P; 11 kg K 26b. In item 26 the plant products remaining on the field are mentioned. This organic material will build up soil humus. No figures are known about this building up on grassland. Kolenbrander (1974) mentioned that after one year 20 kg humus is built up from 100 kg d.m. plant foliage. This means that from the 6000 kg d.m. remaining on the field, 1200 kg humus is produced. We assume a nitrogen content of 4%. Thus, Plant products remaining on the field: 48 kg N 26a. The rest of the nitrogen from 26 and the P and K will become available. Thus, Plant products remaining on the field: 132 kg N; 23 kg P; 150 kg K 19. Dilz and Woldendorp (1960) came to the conclusion that on clay soils 22% of the applied nitrogen is lost. As leaching had been excluded, these losses must be attributed to denitrification. Therefore we assume that 22% of the available nitrogen will be lost by denitrification, thus: Denitrification: 22% of (26a + 8a + 9a + 11 + 15) -- 0.22 × 766 -- 169 kg N ( 2 ) O n a f a r m w i t h 4 c o w s + a c c o m p a n y i n g y o u n g a n i m a l s t h e g r a z i n g is very intense, so only a small part of the grass can be cut. According to Lamm e r s ( 1 9 7 3 ) o n l y 0 . 2 c u t t i n g p e r h a is p o s s i b l e h e r e . ( 3 ) I n t h e t a b l e f o r t h e 2 . 5 - c o w f a r m , a l e a c h i n g o f 3 9 k g N a n d 11 k g K is m e n t i o n e d . T h i s is 5% o f t h e N a n d 3% o f t h e K in t h e p o o l o f a v a i l a b l e s o i l n u t r i e n t s . F o r t h e o t h e r f a r m s t h e s a m e p e r c e n t a g e o f l e a c h i n g is a s s u m e d . ( 4 ) T h e r e a r e n o t a b l e s g i v e n f o r s a n d y soils. O n l y t w o i t e m s a r e d i f f e r e n t , i.e. l e a c h i n g a n d d e n i t r i f i c a t i o n . T h e l e a c h i n g o f K o n s a n d y soil is 1 5 % o f t h e K in t h e p o o l o f a v a i l a b l e s o i l n u t r i e n t s . T h e r e is n o d i f f e r e n c e in l e a c h i n g o f N and P between clay and sandy grassland. Denitrification on sandy grassland is 1 6 % i n s t e a d o f t h e 2 2 % o n c l a y s o i l s ( D i l z a n d W o l d e n d o r p , 1 9 6 0 ) .

92

TABLE 28 System type: Intensive arable

Summary of nutrient flows (units: kg ha-'

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no. Henkens-5 Nutrient

N

Changes in amount SUPPLIES:

REMOVALS:

y-' )

D u t c h a r a b l e f a r m , c r o p r o t a t i o n , c l a y soil, b e e t t o p s p l o u g h e d in ( 3 5 0 0 0 k g h a - f ) , ~ e r y h i g h u s e of fertilizers P

K

of plant component

29. 30t. 30r. 31.

Input by Transfer Transfer Input by

seeds or seedlings ............... by net uptake from soil ........... b y n e t u p t a k e f r o m soil uptake from atmosphere .......... TOTAL

2+

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by plant production remaining on field Transfer by seed for sowing ............. TOTAL

0.5 +

} 195 + -197 .

--.:126 + . 71 + ~ -: 198

SUPPLIES-REMOVALS

0

20 +

35 + -35.5

206 + -226

--25 + 10.5 + -35.5

--107 + 119 + -226

0

0

C h a n g e s in a m o u n t o f a n i m a l c o m p o n e n t SUPPLIES:

1.

2. 3. 4. REMOVALS:

5. 6. 7. 8. 9.

Input by Input by Transfer Transfer

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

. . .

Output by animal products ........... .... O u t P u t b y l o s s e s f r o m m a n u r e t o air, b e f o r e application ......................... Output by manure .................... Transfer by application of manure and/or waste . Transfer by droppings on grazed areas ....... TOTAL

--

SUPPLIES-REMOVALS C h a n g e s in a m o u n t SUPPLIES:

REMOVALS:

o f t o t a l soil c o m p o n e n t

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . by droppings on grazed areas ....... application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . b y s e e d f o r sowingTOTAL ..............

19. 20. 21. 22. 23. 28. 30.

Output by denitrification. ............... Output by volatilization of ammonia . . . . . Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off.. Transfer by net uptake from soil by plant ..... TOTAL SUPPLIES-REMOVALS

--

--0

--

24 +

142 +

--1"

---.5*

10.5 + 35.5

11 ~+ 266

--

--

195 + 324

. O* ---35 + 35

---206 + 246

66

+0.5

+20

--0 305 + 0 --

14' 71 + 3"90 71 + . . 50* ---

.

0

40*

93

T A B L E 28 ( c o n t i n u e d ) S y s t e m t y p e : I n t e n s i v e arable

Summary of r i u t r i e n t f l o w s ( u n i t s : k g h a -1 ~=~ )

T y p e o f f a r m o r e c o s y s t e m or t y p e o f p a r t o f a f a r m o r e c o s y s t e m , ref. no. H e n k e n s - 5

D u t c h arable f a r m , c r o p r o t a t i o n , clay soil, b e e t t o p s p l o u g h e d in ( 3 5 0 0 0 k g / h a ) , v e r y high use o f fertilizers

Nutrient C h a n g e s in a m o u n t o f available soil n u t r i e n t s SUPPLIES :

REMOVALS:

N

P

K

---

---24 ---1 0 0 10.5 0 35.5

---

.

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

Transfer Transfer I n p u t by I n p u t by Input by Input by Input by Input by Transfer Transfer Transfer Transfer

19. 20~ 21. 22. 23. 24. 25.

O u t p u t by d e n i t r i f i c a t i o n . . . . . . . . . . . . . . . . 71 O u t p u t by volatilization o f a m m o n i a . . . . . . . . 0 Output by leaching .................... 58 O u t p u t by r u n - o f f o f available n u t r i e n t s . . . . . . -Output by dust ...................... -T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n 4 5 Transfer by net uptake by the plant . . . . . . . . . Transfer by net'uptake by theplant ......... J 195 TOTAL 369

30t.

30r.

by application of manure and/or waste . by d r o p p i n g s on g r a z e d areas . . . . . . . applica'tion o f m a n u r e . . . . . . . . . . . . fertilizers . . . . . . . . . . . . . . . . . . . . N-fixation .................... a p p l i c a t i o n o f litter, s l u d g e a n d w a s t e . irrigation and flooding . . . . . . . . . . . dry and wet deposition ........... b y w e a t h e r i n g o f soil m i n e r a l f r a c t i o n . . b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n b y p l a n t p r o d u c t i o n r e m a i n i n g on field . b y seed f o r s o w i n g . . . . . . . . . . . . . . TOTAL

SUPPLIES-REMOVALS

305 0 --

-14 ~- ~ 45 71 0 435

142 ---5 0 -119 -266

--0 -----

--40 ---

35 35

206 246

+66

+0.5

+20

--

--

45 0 45

----0 O O

45 0 45

O 0 0

O 0 0

0

0

0

--

C h a n g e s in a m o u n t o f soil o r g a n i c m a t t e r SUPPLIES:

8b. T r a n s f e r 9b. T r a n s f e r 10b. I n p u t b y 13b. I n p u t b y 25. Transfer 26b. T r a n s f e r

R E M O V A L S : 17. 28.

by application and/or waste ....... : b y d r o p p i n g s on g r a z e d areas . . . . . . . application of manure ............ a p p l i c a t i o n o f litter, s l u d g e a n d w a s t e . b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n b y p l a n t p r o d u c t s r e m a i n i n g o n field . . TOTAL

Tr~msfer by m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n O u t p u t by organic matter, removed by r u n - o f f . . TOTAL SUPPLIES-REMOVALS

C h a n g e s in a m o u n t o f soil m i n e r a l s SUPPLY: REMOVAL:

24. 16.

T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y w e a t h e r i n g o f soil f r a c t i o n . . . . . . . SUPPLY-REM()VAL

---

--0 0

94

T A B L E 29 S y s t e m t y p e : I n t e n s i v e arable

Summary of n u t r i e n t f l o w s ( u n i t s : kg h a -1 y - i )

T y p e o f f a r m or e c o s y s t e m o r t y p e o f p a r t o f a f a r m o r e c o s y s t e m , ref. no. H e n k e n s - 6

D u t c h arable f a r m c r o p r o t a t i o n , clay soil, b e e t t o p s (35 0 0 0 k g h a - ) r e m o v e d , v e r y h i g h use o f fertilizers

Nutrient

N

P

K

2 195

0.5 35

20 206

-197

-35.5

-226

--

--

166 31

--31 4.5

154 72

197

35.5

226

C h a n g e s in a m o u n t o f p l a n t c o m p o n e n t

SUPPLIES:

REMOVALS:

29. Input by seeds or seedlings . . . . . . . . . . . . . . . 30t. Transfer by net uptake from soil . . . . . . . . . . . 30r. Transfer by net uptake from soil . . . . . . . . . . . 31.

Input by uptake from atmosphere TOTAL

..........

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . Transfer by grazing of forage . . . . . . . . . . . . . Output by primary products .............. T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g on field . T r a n s f e r b y seed f o r s o w i n g . . . . . . . . . . . . . . TOTAL

}

SUPPLIES-REMOVALS

0

0

0

C h a n g e s in a m o u n t o f a n i m a l c o m p o n e n t SUPPLIES:

1.

2. 3.

4. REMOVALS:

5. 6. 7. 8. 9.

Input by Input by Transfer Transfer

feed for livestock . . . . . . . . . . . . . . . l i t t e r used i n d o o r s . . . . . . . . . . . . . . by consumption of harvested crops by g r a z i n g o f f o r a g e . . . . . . . . . . . . . TOTAL

. . .

Output by animal products ............... O u t p u t b y losses f r o m m a n u r e to air, b e f o r e application~l|, . . . . . . . . . . . . . . . . . . . . . . . . . Output by manure .................... Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s o n g r a z e d areas . . . . . . . TOTAL

--

SUPPLIES-REMOVALS C h a n g e s in a m o u n t o f total soil c o m p o n e n t SUPPLIES:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

R E M O V A L S : 19. 20. 21. 22. 23. 28. 30.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure . . . . . . . . . . . . fertilizers . . . . . . . . . . . . . . . . . . . . N-fixation .................... a p p l i c a t i o n o f litter, s l u d g e a n d w a s t e . irrigation and flooding . . . . . . . . . . . dry and wet deposition . . . . . . . . . . . b y p l a n t p r o d u c t s r e m a i n i n g on field . . b y seed f o r s o wTi nOgT A. L .............

Output by denitrification ................ Output by volatilization of a m m o n i a . . . . . . . . Output by leaching . . . . . . . . . . . . . . . . . . . . O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . Output by dust ...................... Output by organic matter, removed by r u n - o f f . . T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL SUPPLIES-REMOVALS

-0 332 0 --14 31 --7 37

--0 30 ---1 4.5

-0 189 --5 72

35.5

266 --40 --

195 324

--0 ---35 35

-206 246

+5~3

+0.5

+20

71 0 58 --

95

T A B L E 29 ( c o n t i n u e d ) S y s t e m type: Intensive arable

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -1 y - i )

T y p e o f f a r m or e c o s y s t e m o r t y p e o f p a r t o f a f a r m or e c o s y s t e m , ref. n o . H e n k e n s - 6

D u t c h arable f a r m , c r o p r o t a t i o n , clay soil, b e e t t o p s (35 0 0 0 k g h a -~ ) r e m o v e d , v e r y h i g h u s e o f fertilizers

Nutrient

N

P

--

---30 ---1 --4.5 -35.5

K

C h a n g e s in a m o u n t o f available soil n u t r i e n t s SUPPLIES:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16.

17. 26a. 27. R E M O V A L S : 19. 20. 21. 22. 23. 24. 25. 30t. 3Or.

Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s on g r a z e d areas . . . . . . . Input by application of manure ............ I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . Input by N-fixation. ................... I n p u t b y a p p l i c a t i o n o f l i t t e r , sludge a n d w a s t e . I n p u t by irrigation and flooding . . . . . . . . . . . Input by dry and wet deposition . . . . . . . . . . . T r a n s f e r b y w e a t h e r i n g o f soil m i n e r a l f r a c t i o n . . T r a n s f e r b y m i n e r a l i z a t i o n o f soil o.r~anic f r a c t i o n T r a n s f e r b y p l a n t p r o d u c t i o n r e m m m n g on field . T r a n s f e r b y seed f o r s o w i n g . . . . . . . . . . . . . . TOTAL O u t p u t by d e n i t r i f i c a t i o n . . . . . . . . . . . . . . . . O u t p u t by volatilization of a m m o n i a . . . . . . . . Output by leaching . . . . . . . . . . . . . . . . . . . . O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . Output by dust ...................... T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n Transfer by net uptake by the plant T r a n s f e r by n e t u p t a k e b y t h e p l a n t i~ii~i~i} TOTAL SUPPLIES-REMOVALS

-332 0 -14 45 31 -422 71 0 58 --

--189 --5 --72 -266 --40 --

45

--0 -----

195 369

35 35

206 246

+53

+0.5

+20

--

--

45

------0

45 0 45

0 0 0

0 0 0

0

0

0

--

C h a n g e s in a m o u n t o f soil o r g a n i c m a t t e r SUPPLIES:

8b. 9b. 10b. 13b. 25. 26b.

R E M O V A L S : 17. 28.

Transfer Transfer Input by Input by Transfer Transfer

by application and/or waste ........ b y d r o p p i n g s on g r a z e d areas . . . . . . . application of manure ............ a p p l i c a t i o n o f litter, sludge a n d w a s t e . b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n b y p l a n t p r o d u c t s r e m a i n i n g on field . . TOTAL

T r a n s f e r b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n Output by organic matter, removed by r u n - o f f . . TOTAL

45

SUPPLIES-REMOVALS C h a n g e s in a m o u n t o f soil m i n e r a l s SUPPLY: REMOVAL:

24. 16.

T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y w e a t h e r i n g o f soil f r a c t i o n '. . . . . . . SUPPLY-REMOVAL

--

---0

96

Arable farming Classification. Two almost identical crop rotation systems are compared to each other; one in which the tops of beets are removed and another one in which the tops are ploughed in. Intensive arable system. Reference: Henkens-5; Dutch arable farm, clay soil, crop rotation, beet tops ploughed in, Table 28. Intensive arable system. Reference: Henkens-6; Dutch arable farm, clay soil, crop rotation, beet tops removed, Table 29. On an arable farm different crops are grown, and so the mean annual removal should be based on a rotation. The following is taken as a crop rotation: potatoes, wheat, sugar beets, wheat. This is a frequent rotation in The Netherlands. Table 27 shows the yields and the nutrient contents. The yield hardly influences the nutrient content and so the removal is determined by yield. The same table shows the quantity of crop residues expressed in dry matter (Anonymus, 1973a). A distinction has been made between areas from which tops and leaves of sugar beets are sold and areas where these products are ploughed in. TABLE 27 Yields of harvested crop (fresh material), crop residues (dry material) and their nutrient contents Harvested crop Yield Potatoes Wheat: seed straw Sugar beets: beets tops + leaves

45 5 5 50 35

000 500 000 000 000

kg kg kg kg kg

Crop residue N~oo

P%o

K~oo

Amount

N%

P%

3,0 19.1 5.1 2.1 4.6

0.6 3.7 0.8 0.5 0.6

4.6 4.2 8.1 1.9 5.3

3 500 kg 4 500 kg

1.3 0.6

0.13 3.1 0.09 0.9

1 500 kg

0.9

0.22 0.8

Tables 28 and 29 give the nutrient flow in kg ha -1 y-1 of crop land as a mean of the rotations mentioned, on a marine clay soft. The nitrogen flow requires further discussion. The harvested part of the crops (beet tops and leaves included) take up 166 kg N. According to the results of field experiments, 50% of the nitrogen given is stored in the harvested crop (Sluysmans, 1966). Thus 332 kg N fertilizer is needed, the other 5 0 % being stored in the plant products remaining on the field or disappearing by leaching or denitrification and volatilization. According to the results of Van der Paauw and Ris (1963}. 13.5% of the nitrogen, which is n o t taken up by the harvested crop, will be available in the following year. This after-effect depends on the rainfall. This means that 0.135 X 166 = 22 kg N will remain in the soil.

K~

97 In the case where the beet tops and leaves are removed, 3500 kg dry matter containing 29 kg N remains on the fields. According to Kolenbrander (1974), 30--35 kg humus will be formed after one year from 100 kg dry matter of plant residues. This means that from 3500 kg dry matter of plant residues 0.32 X 3500 kg = 1120 kg humus (4% N) will be formed, containing 45 kg N. This means that 45 - 29 = 16 kg of additional N is b o u n d by the new humus. These 16 kg N are obtained from the fertilizer nitrogen or from the nitrogen delivered by breakdown of soil humus. We will assume that there is equilibrium between breakdown and building up of humus in our examples. Thus the breakdown of soil humus will yield 45 kg N, so that the net result is an enrichment of available nitrogen in the soil of 29 kg N. In the case where the sugar beet tops and leaves are ploughed in, an extra a m o u n t of 5250/4 kg dry matter per year containing 40 kg N is supplied to the soil. From this material 0.25 × 1312 = 328 kg humus, containing 13 kg N, will be formed after one year. Thus, by ploughing in the tops and leaves from sugar beets an extra 40 - 13 = 27 kg available N is supplied. This amount should be subtracted from the N fertilizer needed so that, when beet tops are ploughed in, 305 kg N fertilizer is needed. Of course, in the year directly after sugar beets, more nitrogen can be subtracted. Based on analytical data (Henkens, 1972, 1976) of drainage water on crop land, the leaching (300 mm drainage water) is: on marine clay softs: 58 kg N; 0.2 kg P; 40 kg K on sandy soils: 85 kg N; 0.06 kg P; 48 kg K With the rain water, 14 kg N; 1.0 kg P; and 5 kg K are supplied (Henkens, 1976). Thus, in fact, only 44 kg of the N fertilizer is leached on marine clay soil and 71 kg on sandy soft. From the 332 kg N fertilizer 166 + 22 + 29 + 44 = 261 kg N on marine clay soil is n o w accounted for and on sandy soil 166 + 22 + 24 + 61 = 273 kg N. The rest, 71 or 59 kg respectively, is n o t accounted for. This a m o u n t is lost by denitrification. 6.4. AGRO-ECOSYSTEMS IN GERMANY (B. Ulrich)

Forests in Central Europe Three forest systems have been described. Classification. Forest. Reference: Ulrich-l; Deciduous and coniferous forests, acid softs, northern hemisphere, Table 31. Forest. Reference: Ulrich-2; Coniferous forest on grey-brown podsolic soft, Central Europe (IBP-Solling project), Table 32. Forest. Reference: Ulrich-3; Deciduous forest on grey-brown podsolic soil, Central Europe (IBP-Solling project), Table 33. For forests, some special aspects have to be considered with respect to nutrient cycling.

98

6.4.1. Input Due to their larger extension into the troposphere (tree height 30--40 m), forests have an increased input from the atmosphere by interception of air constituents. Air masses exchanging between the crown space and the boundary layer of the troposphere carry aerosols as well as gases to the leaf surfaces, where they can be adsorbed or dissolved after impaction. The a m o u n t of this additional input by interception depends upon the air impurities, and in forest regions of Central Europe is approximately 5 kg N, 0.1 kg P and 7 kg K per ha and per year. The removal of impurities from the air is, on the one hand, a special contribution of forests to air cleansing, and on the other hand, an appreciable contribution to the nutrient requirement, accounting for approximately 8% of N uptake, 2% of P uptake and 30% of K uptake.

6.4.2. Uptake In contrast to agricultural crops, it is easily possible in a forest to measure and collect the precipitation after passage through the leaf space. Measurements of this kind show that the rain leaches potassium out of the leaves in an a m o u n t comparable to the net uptake, calculated as the sum of forest increment and litter fall. No leaf leaching occurs in the cases of N and P, at least at the low nutrient levels encountered in acid forest soils. Leaf leaching occurs very probably in agricultural crops too. Its neglect is n o t important in a consideration of annual balances, b u t it should be taken into acc o u n t in simulation models because it increases the rate of turnover.

6.4.3. Primary products sold Forests differ from agricultural crops in the time span between two harvests. In a forest with a uniform age structure, approximately half of the annual increment is harvested over a time interval of 15--30 years; the other half is allowed to accumulate on the site and is harvested at the end of the life span of the stand. For ease of comparison, the amounts listed under "primary products sold" correspond to the total mean annual increment, irrespective of the time of harvesting. At a given harvesting time, only part of the accumulated increment m a y be taken o u t of the forest. For example, the bole may be exported, whereas the bark and the branches remain on the forest floor, becoming part of the plant products remaining on the field. Since modern forestry tends to whole-tree logging, the annual increment was considered to belong in total to the primary products sold.

6.4.4. Changes in soil component Forest stands of a uniform age m a y have life spans between 80 years (Douglas fir, Norway spruce) and 240 years (oak). The final harvest (clear cut) means a destruction of the ecosystem, especially if the forest stand has no shrub layer or ground flora. If the vegetation is destroyed in total by

(a) (b) (c) (d) (e) (f) (g) (h) (i) (j) (k) (I)

input by rain input by interception total input t r a n s p o r t b y rain inside s t a n d soil i n p u t b y l i t t e r fall growth increment leaching f r o m soil leaf leaching u p t a k e f r o m soil uptake from atmosphere total uptake c h a n g e in soil reserves

0.90 --1.21 --0.30 ----+1.7 34.4 1.4

5.1 -1.3 -

3.8 7.3 11.1 22.9 16 6.6 5.9 11.8 34.4

K

8.2 3.8 12 12.5 0.7 0.1 10.6 0.5 5.1

H Na (kg h a - l y - i )

F l u x balance o f a b e e c h s t a n d in C e n t r a l E u r o p e (Ulrich, 1 9 7 5 )

T A B L E 30

-

27.2 1.8

13.9 8.6 22.5 26 16 7.7 16.6 3.5 27.2

Ca

3.5 -1.6

2.2 1.3 3.5 3.7 1.6 1.7 3.4 0.2 3.5

Mg

0.9 0.5 1.4 1.2 1.8 0.7 0.1 -0.2 2.3 0.2 2.5 +0.9

Fe

7.6 -6.9

0.6 1.5 2.1 3.0 5.1 3.4 5.6 0.9 7.6

Mn

1.2 0.5 1.7 1.5 0.5 0.1 12.7 - 0.2 0.4 0.2 0.6 -11.1

Al

2.1 - 2.9

17.9 12.5 30.4 31.6 0.8 0.1 33.2 1.2 2.1

CI

8.5 +11.5

24.5 14.9 39.4 44.2 3.2 0.5 27.4 4.8 8.5

S

0.71 0.09 0.8 0.55 4 2.1 0.05 -0.25 5.85 0.25 6.1 -1.35

P

23.7 4.8 28.5 24.7 49 13 6 - 3.8 58.2 3.8 62 + 9.4

N

100

T A B L E 31 System type: Extensive forestry

Summary of nutrient flows (units: kg ha-'

T y p e o f farm or e c o s y s t e m or t y p e o f part o f a f a r m o r e c o s y s t e m , ref. n o . U l r i c h - 1

y-' )

D e c i d u o u s a n d c o n i f e r o u s f o r e s t s , a c i d soils, northern hemisphere

Nutrient

N

P

K

-50--80 -0--5 50--80

-4.5--9 --4.5--9

-11--28 --11--28

t t 10--20 40--60

t t 1.5--3 3 --6 -4.5--9

t t

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

29. 30t. 30r. 31.

Input by Transfer Transfer Input by

seeds or seedlings ............... b y n e t u p t a k e f r o m soil . . . . . . . . . . . by net uptake from soil ........... uptake from atmosphere .......... TOTAL

REMOVALS:

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by plant production remaining on field . Transfer by seed for sowing .............. TOTAL

50--80

SUPPLIES-REMOVALS

0

5--10 6--18 11--28

0

0

Changes in a m o u n t o f animal c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4.

Input by Input by Transfer Transfer

5. 6.

Output by animal products ............... O u t p u t b y losses f r o m m a n u r e t o air, b e f o r e application ......................... Output by manure .................... Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s o n g r a z e d areas . . . . . . . TOTAL

7. 8. 9.

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

. . .

--

SUPPLIES-REMOVALS Changes in a m o u n t o f t o t a l soil c o m p o n e n t SUPPLIES:

REMOVALS:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field • . by seed for sowing .............. TOTAL

19. 20. 21. 22. 23. 28. 30.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off . . Transfer by net uptake from soil by plant ..... TOTAL SUPPLIES-REMOVALS

-t

-t

-t --5--30 40--60 -45-90 t -1--20 t --50--80 51--100 (-10)---20

-t

-----0.5--1 3 --6 -3.5--7 --0.05 t --4.5-9 4.5-9 (-2)--2

----1--10 6--18 -7--28 --1--8 t --11--28 13--32 (-

5)-5

101

TABLE

31 ( c o n t i n u e d )

System type: Extensive forestry

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -1 ~y-I )

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref, n o . U l r i c h - 1

D e c i d u o u s a n d c o n i f e r o u s f o r e s t s , a c i d soils, northern hemisphere

Nutrient

N

P

K

C h a n g e s in a m o u n t o f a v a i l a b l e s o i l n u t r i e n t s SUPPLIES:

REMOVALS:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27. 19. 20. 21. 22. 23. 24. 25. 30t. 30r.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer Transfer Transfer

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by weathering of soil mineral fraction.. by mineralization of soil organic fraction by plant production remaining on field . by seed for sowing .............. TOTAL

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Transfer by f i x a t i o n in soil m i n e r a l fraction . . . . Transfer by i m m o b i l i z a t i o n in soil organic fraction T r a n s f e r b y n e t u p t a k e hb vy ~thh,e, l ap nl at n t .. .. .. .. .. .. .. .. .. Transfer by'net uptake

--

-t --

t --

------

t --5--30

---0.5--1 0 --2

--

3

40--70 ---

1--10 0--5

--6

6--18

--45--100

--3.5--9

t --

7--32

--1--20

t ---

--0.05

t

0--10 --50--80

Ydfihf~

SUPPLIES-REMOVALS

--

t

1--8 t

--

--

0--2 -4 -- .5--9

0--5 -1 -- 1--28

51--110

4.5--11

(-10)--10

12--41

0

0

Changes in a m o u n t o f soil organic m a t t e r SUPPLIES:

8b. 9b.

Transfer by application and/or waste ........ Transfer by d r o p p i n g s on grazed areas . . . . . . .

10b. I n p u t b y a p p l i c a t i o n o f m a n u r e . . . . . . . . . . . .

REMOVALS:

-t --

--

--

t

t ---

---

13b. • 25. 26b.

Input by application of litter, sludge and waste . Transfer by i m m o b i l i z a t i o n in soil organic fraction Transfer by plant products remaining on field . . TOTAL

0--10 40--60 40--70

3--6 3--6

6--18 6--18

17. 28.

Transfer by mineralization of soil organic fraction Output by organic matter, removed by run-off . . TOTAL

40--70 0 40--70

3--6 0 3--6

6--18 0 6--18

SUPPLIES-REMOVALS

(-10)--10

( - 1)---0

0

Changes in amount of soil minerals SUPPLY: REMOVAL:

24. 16.

Transfer by f i x a t i o n in soil m i n e r a l fraction . . . . Transfer by weathering of soil fraction ....... SUPPLY-REMOVAL

---

0--2 0--2 (-2)--2

0--5 0--5 (-5)--5

102

TABLE 32 S y s t e m t y p e : E x t e u s ! v e forestkT

Summary of n u t r i e n t f o w s (units: k g h a - I y - I )

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref. n o . Ulrich-2

C o n i f e r o u s f o r e s t o n g r e y - b r o w n p o d s o l i c soil, C e n t r a l E u r o p e (IBP Soiling P r o j e c t )

Nutrient

N

P

K

~* -(4)59

5* -5

22" -2--2

--

--1.4, 3.6 -5

C h a n g e s in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

REMOVALS:

29. 30t. 30r. 31.

I n p u t b y seeds o r seedlings . . . . . . . . . . . . . . . T r a n s f e r b y n e t u p t a k e f r o m soil . . . . . . . . . . . T r a n s f e r b y n e t u p t a k e f r o m soil . . . . . . . . . . . Input by uptake from atmosphere .......... TOTAL

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g o n field . Transfer by seed for sowing .............. TOTAL

, 12, 47 59

SUPPLIES-REMOVALS

0

--

78* 14 21.8

0

0

C h a n g e s in a m o u n t o f a n i m a l c o m p o n e n t SUPPLIES:

1. 2. 3. 4.

REMOVALS:

5. 6. 7. 8. 9.

I n p u t b y feed f o r l i v e s t o c k . . . . . . . . . . . . . . . Input by litter used indoors .............. Transfer by consumption of harvested crops Transfer by grazing of forage ............. TOTAL

. . .

Output by animal products ............... Outp.ut b y losses f r o m m a n u r e t o air, b e f o r e application ......................... Output by manure .................... Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s o n g r a z e d areas . . . . . . . TOTAL

--

SUPPLIES-REMOVALS C h a n g e s in a m o u n t o f t o t a l soil c o m p o n e n t SUPPLIES:

REMOVALS:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer by application of manure and/or waste T r a n s f e r b y d r o p p i n g s o n grazed a r e a s . . . Input by application of manure . . . . . . I n p u t b y fertilizers . . . . . . . . . . . Input by N-fixation ..................... I n p u t b y a p p l i c a t i o n o f litter 2 sludge a n d w a s t e Input by imgation and floodmg . . . . . Input by dry and wet deposition ........... T r a n s f e r b y p l a n t p r o d u c t s r e m a i n i n g o n field . Transfer by seed for sowing . . . . . . . TOTAL

19. 20. 21. 22. 23. 28.

Output by danitrification . . . . . . . . . Output by volatilization of ammonia ........ Output by leaching .................... O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . Output by dust ...................... Output by organic matter removed by run-off.. T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL

30.

SUPPLIES-REMOVALS

.

.

. . . . . . . . . . . . . . . . . . . . "Z . . . . . . . . . . . 29 + 0.8* 47 3.6 . . . . . . . . . 76 4.4

. . . . . . . .

.

.

.

. . .

. . -17" ----

.

.

.

.

.

0.02* ----

59 76 0

.

11 + 14 25

. 2* ----

5 5

22 24

-0.6

+1

103

T A B L E 32 ( c o n t i n u e d ) System type: Extensive forestry

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -1 y - i )

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref. n o . U l r i c h - 2

Coniferous forest on grey-brown podsolic soil, Central Europe (IBP-Solling Project)

Nutrient

N

P

K

-------

--------

Changes in amount of availablesoil nutrients SUPPLIES:

8a. 9a. 10a.

11. 12. 13a. 14.

REMOVALS:

Transfer Transfer Input by Input by Input by Input by Input by

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ...........

15. 16.

Input by dry and wet deposition . . . . . . . . . . . Transfer by weathering of soil mineral fraction..

29

17. 26a. 27.

Transfer by mineralization of soil organic fraction Transfer by plant production remaining on field . Transfer by seed for sowing .............. TOTAL

47 --

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Transfer by fixation in soil mineral fraction .... Transfer by immobilization in soil organic fraction Transfer by net uptake by the plant ......... Transfer by net uptake by the plant ......... TOTAL

--

19. 20. 21. 22. 23. 24. 25. 30t. 30r.

76

17 --

59 -76

SUPPLIES-REMOVALS

-------

0.8

11

(3.60"6) --5.0

140 --

---

--

25

0.02 ----5.0

0.6 -22 -24.6

0

+0.4

3.6 3.6

-----14 14

5 --

0

2 --

Changes in amount of soil organic matter SUPPLIES:

REMOVALS:

8b. Transfer 9b. Transfer 10b. Input by 13b. Input by 25. Transfer 26b. Transfer 17. 28.

by application and/or waste ........ b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ application of litter, sludge and waste . by immobilization in soil organic fraction by plant products remaining on field - • TOTAL

Transfer by mineralization of soil organic fraction Output by organic matter, removed by run-off.. TOTAL

-----

------

47 47 (47) 0 47

SUPPLIES-REMOVALS

0

(3.6) 0 3.6

(14) 0 14

0

0

0 0.6

0.6 0

- 0.6

+ 0.6

Changes in amount of soil minerals SUPPLY: REMOVAL:

24. 16.

Transfer by fixation in soil mineral fraction .... Transfer by weathering of soil fraction ....... SUPPLY-REMOVAL

-0

104

TABLE 33 System type: Extensive forestry

Summary of nutrient flows (units: kg ha-'

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no. Ulrich-3

Deciduous forest on grey-brown podsolic soil, Central Europe (IBP-Solling project)

Nutrient C h a n g e s in a m o u n t SUPPLIES:

REMOVALS:

29. 30t. 30r. 31. 3. 4. 18. 26. 27.

SUPPLIES:

REMOVALS:

Input by Transfer Transfer Input by

seeds or seedlings ............... b y n e t u p t a k e f r o m soil . . . . . . . . . . . b y n e t u p t a k e f r o m soil . . . . . . . . . . . uptake from atmosphere TOTAL ..........

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by plant production remaining on field . Transfer by seed for sowing .............. TOTAL

P

K

-59* --

-~, o --

-23* --

~3~

6*

23*

--13: 49 -62

--2.1"

--16.6:

-6.1

-22.6

0

0

0

of animal component

1. 2. 3. 4.

Input by Input by Transfer Transfer

5. 6.

Output by animal products ............... Output by losses from manure to air, before application ......................... Output by manure ~ ................... Transfer by application of manure and/or waste . Transfer by droppings on grazed areas ....... TOTAL

7. 8. 9.

N of plant component

SUPPLIES-REMOVALS C h a n g e s in a m o u n t

y-, )

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

. . .

--

SUPPLIES-REMOVALS C h a n g e s in a m o u n t SUPPLIES:

REMOVALS:

o f t o t a l soil c o m p o n e n t

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . . by droppings on grazed areas . . . . . . application of manure . . . . . . . . . . fertilizers .................... -N-fixation .................... -application of litter, sludge and waste . -irrigation and flooding ........... dry and wet deposition ........... 28: by plant products remaining on field . . 49 by seed for sowing .............. -TOTAL 77

19. 20. 21. 22. 23. 28. 30.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off . . T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL SUPPLIES-REMOVALS

-6* ---62* 68 +9

. . .

. . .

. . . . . ----0.8:

----

-4.8

11.* 16 -27

--

--

0.05* ---

6 ---

6* 6.1

23* 29

-1.3

-2

105

T A B L E 33 ( c o n t i n u e d ) System type: Extensive forestry

Summary of n u t r i e n t flows (units: kg h a - l ~f-i )

T y p e o f f a r m o r e c o s y s t e m or t y p e o f p a r t o f a f a r m o r e c o s y s t e m , ref. no. Ulrich-3

D e c i d u o u s forest o n g r e y - b r o w n podsolic soil, Central E u r o p e (IBP-Solling Project)

Nutrient

N

P

K

---

-------

---

Changes in a m o u n t o f available soil n u t r i e n t s SUPPLIES:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

R E M O V A L S : 19. 20. 21. 22. 23. 24. 25. 30t. 30r.

Transfer by application of m a n u r e and/or waste . T r a n s f e r b y d r o p p i n g s o n grazed areas . . . . . . . Input by application of m a n u r e . . . . . . . . . . . . I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . I n p u t b y N-fixation . . . . . . . . . . . . . . . . . . . . I n p u t b y a p p l i c a t i o n o f litter, sludge and w a s t e . I n p u t b y irrigation and flooding . . . . . . . . . . . I n p u t b y d r y and w e t d e p o s i t i o n . . . . . . . . . . . T r a n s f e r b y w e a t h e r i n g o f soil m i n e r a l f r a c t i o n . . T r a n s f e r b y m i n e r a l i z a t i o n o f soil organic f r a c t i o n T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g o n field . T r a n s f e r b y seed for s o w i n g . . . . . . . . . . . . . . TOTAL O u t p u t by denitrification . . . . . . . . . . . . . . . . O u t p u t b y volatilization o f a m m o n i a . . . . . . . . O u t p u t b y leaching . . . . . . . . . . . . . . . . . . . . O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . O u t p u t b y dust . . . . . . . . . . . . . . . . . . . . . . T r a n s f e r b y fixation in soil m i n e r a l fraction . . . . T r a n s f e r b y i m m o b i l i z a t i o n in soil organic f r a c t i o n T r a n s f e r b y n e t u p t a k e b y ,the p l a n t . . . . . . . . . Transfer by net uptake b y t h e p l a n t . . . . . . . . . TOTAL

28 49 -77 ---6 -9 62 77

SUPPLIES-REMOVALS

0.8, 1.3 4 --6.1 --0.05 ----6 -6.1

-11, 16 --29 --

6 --23 29

0

0

0

Transfer by application and/or waste . . . . . . . . T r a n s f e r b y d r o p p i n g s on grazed areas . . . . . . . Input by application of manure . . . . . . . . . . . . I n p u t b y a p p l i c a t i o n o f litter, sludge a n d w a s t e . T r a n s f e r b y i m m o b i l i z a t i o n in soil organic fraction ( 9 ) T r a n s f e r b y p l a n t p r o d u c t s r e m a i n i n g on field . . 49 TOTAL 58

-4 4

-16 16

T r a n s f e r b y m i n e r a l i z a t i o n o f soil organic fraction O u t p u t b y organic m a t t e r , r e m o v e d b y r u n - o f f . . TOTAL

(49) -49

4* -4

16' -16

+ 9

0

0

---

-1.3

-2

-1.3

-2

Changes in a m o u n t o f soil organic m a t t e r SUPPLIES:

8b. 9b. 10b. 13b. 25. 26b.

R E M O V A L S : 17.

28.

SUPPLIES-REMOVALS Changes in a m o u n t o f soil minerals SUPPLY: REMOVAL:

24. 16.

T r a n s f e r b y fixation in soil m i n e r a l fraction . . . . T r a n s f e r b y w e a t h e r i n g o f soil f r a c t i o n . . . . . . . SUPPLY-REMOVAL

106

clear cutting, nutrient losses, especially nitrogen losses, may occur by increased mineralization of soil organic matter and the cessation of plant uptake. The nitrogen losses may reach 500 kg N ha- ' , in extreme cases even 1000 kg N ha- ' , if, as a consequence of clear cutting and soil cultivation, the m o t layer on top of the mineral soil is decomposed completely. On an annual basis this corresponds to average nitrogen losses of 0--5 (--10) kg N ha- ' y- ' in a coniferous forest region, assuming that the stands have a mean life span of 100 years and a balanced age distribution.

6.4.5. Measurement and calculation o f nutrient fluxes To describe the nutrient fluxes in a forest, Fig. 3 is acceptable only as a summary; for calculating the actual fluxes a more refined model is required. The following fluxes can be measured in the field by measuring the flow rate of the transport medium and its bioelement concentration. (Comparable fluxes in Fig. 3 are indicated with their usual numbers): (a) Input by rain (compare 31) (b) Input by interception by the canopy and bark (see Mayer and Ulrich, 1974) (compare 31) (c) Total input = (a) + (b) (compare 31) (d) Transport by rain inside stand (sum of canopy drip and stem flow) (no comparable flux, may be included in 26) (e) Flow by litter fall (compare 26) (f) Growth increment (does n o t exist in Fig. 3) (g) Leaching from soil (water collection by suction lysimeter plates or candles) (compare 21) (h) Leaf leaching and (j) uptake from the atmosphere = (d) - (c) (compare 15) (i) Uptake from soil = (e) + (f) + (h) (compare 30) (k) Total uptake = (i) + (j) (compare 30+ 31) (1) Change in soil reserves = (c) - (f) - (g) (not applicable) Table 30 shows a flux balance of a beech (Fagus silvatica) forest which may be used to outline the measurement and calculation of nutrient fluxes as described before. The ranges for nutrient flows shown in Table 31 for deciduous and coniferous forest stands with a regular age structure on acid soils of the northern hemisphere are taken from a set of IBP data (Ulrich et al., 1974).

107

6.5. AGRO-ECOSYSTEMS IN FRANCE (P. Jacquard) The nutrient cycling scheme as presented in Fig. 3 is in fact a very simplified one because the role of the microflora in the soil is not taken into acc o u n t as a separate storage level for nutrients. We use schemes as presented in Figs. 4--12 to describe the cycling within the soil system. These figures describe h o w much of the fertilizer which was added at a certain time will be available for the next crop. This depends in particular on the fraction of pastures which is used for grazing. We have differentiated between the following systems: System A (French farm, all in pasture lands, without fertilizers); System B (French farm, 75% of leys used by grazing); System C (French farm, 50% of leys used by grazing); System D (French farm, 25% of leys used by grazing); System E (French farm, no use of leys by grazing); System F (French farm, forage production without animals). The farms m a y be dairy and/or meat oriented, except, of course, in system F. The figures do not refer to areas in the farm, or to years in the same plot, but to the type of use of the forage production. Arable parts of the system were excluded; they were used only to test the availability of soil nutrients after leys. As regards the kind vegetation types, A is a mixed vegetation of permanent grassland, B may be a simple mixture (one grass + white glover), C (sysCarried off ,(5)0 Meat and/or mitk ~e/Livestock

Carried off

Herbage

(11)/ /

//

//(30t÷r)

idue \ (26) / / //~ e×creta ~ . E * c r e t a

;// . ~26÷9) [/~/ (26a+ga) ( e= ~IDP'/Microftorait)

Ava itabte (t) (16+1

(12)

b+gb) Soil reserves it) From time (t) to time ( t + l )

I/

~Microftora (t+,) \" (Sa) >% ~ 0 Avaitab,e ( Soil reserves (t÷l)

Fig. 4. The cycling o f n u t r i e n t s in t h e soil (fluxes are indicated according to Table 3). --~increase;--~ decrease; ~'~ a n a b o l i c processes; ~-~ f e e d b a c k l o o p s increasing the stability o f t h e system.

108

90

Uv~es~20°ck

e~ock

/

Fixed

9.5

mt

J

Leached

50

• Soil reserves = - 7

Sol [ reserves = - 20

Fig. 5 (left). The cycling of N (kg h a -~ ) in system Jacquard-1. Fig. 6 (right). T h e cycling o f P (kg h a -~ ) in system Jacquard-1.

///•t

• Livestock

7/ /

av. t

300 mt

X e l

,

12

P

,=Leached

Sol[ reserves = - 20 Fig. 7. The cycling o f K (kg ha -~ ) in system Jacquard-1.

tern Jacquard--3) consists of pure legumes, whilst C (system Jacquard--4) and the systems D, E, and F are pure grass. An overview of the systems is shown in Table 34. The Tables 36--43 show the nutrient balances in the usual way. References: Tables 36--42, Jacquard, 1972; Table 43, Specty and Mettauer, 1971; Coppenet, 1975. The leaching data used are equal for all systems(50 kg N ha- 1 y- 1 ) and are derived from French literature (Table 35).

Reference

Jacquard-1 Jacquard-2 Jacquard-3 Jacquard-4 Jacquard-5 Jacquard-6 Jacquard-7 Jacquard-8

Description

Extensive livestock Intensive m i x e d Intensive m i x e d Intensive m i x e d Intensive m i x e d Intensive m i x e d Intensive arable (grass) Intensive horticulture

Agro-ecosystems in France

T A B L E 34

A B C C D E F --

System type according to Jacquard 100 75 50 50 25 0 0 --

Grazing (%)

0 25 50 50 75 100 100 --

Cutting (%)

0 100 0 200 400 800 800 50

N Fertilizer ( k g h a -1 y - I )

(50) (50) 60 (50) t t t t

N fixation ( k g h a -1 y-~ )

5,6 and 7 8 -9 10 11 12 --

Figure(s)

36 37 38 39 40 41 42 43

Table

O cD

110 T A B L E 35 Output of nutrients by leaching (kg ha -1 y - ' ) Reference

N

P

K

Specty and Mettauer, 1971 Coppenet, 1975 Gachon, 1974: Annual forage crop Ley Natural grassland

45 50 14 2--7 0--11

-1 ----

3 10--20 19--22 10 6--7

Fert:zersHr '

ck

/ o ~ ~ 1~esidues\ ~ ,01 >o 2oo/XExcr.,. I

.v ~/,oo

mt

•t e~

Fix~

•

f

~30 ,~ !.v,.,

/

mt÷ 1 ~

~ . /

50

crop /,3o

/

50 SoiL reserves = +40

Le~ched

4O

,~111

'

~./

s.n t + 1 =-60

Fig. 8. The cycling o f N (kg ha-' ) in system Jacquard-2.

Herbage~/fi •/

Fertilizers

200~> 0 0 1 / av.t

~/
60 cm) and textures (except very sandy or very clayey).

6.7.2.3. Vegetation. All areas with arable soils are either actually cultivated for crops, or covered by a segetal vegetation of winter annuals, which dominates abandoned fields for many years. The crops are mainly winter grains, i.e. wheat and barley. The segetal " p a s t u r e " vegetation includes grasses (Phalaris minor, Hordeum murinum, Stipa capensis), forbs (Erucaria boveana, Anthemis melanolepsis, Centaurea iberica) and legumes ( Trigonella arabica). 6.7.2.4. Land use and management. Different types of land use and management exist in the region, e.g.: (a) Natural pastures used by nomadic flocks of sheep and goats, at fluctuating densities. (b) Winter grain crops (wheat, barley) grown with no direct input of fertilizer and manure; the stubble is gathered as straw, or grazed by animals in summer. (c) Winter grain crops (wheat) with high inputs of nitrogen fertilizer (about 100 kg N ha- ~ ) each year. (d) Intensive natural or sown pasture, grazed permanently by sheep; with or without fertilizer inputs. Types (a) and (b) have existed in the region almost unchanged for a b o u t 5000 years and are still practised by part of the Bedouin population. Type (c) is n o w dominant in the modern Jewish agriculture in the Negev and is being gradually adopted also by the Bedouin. T y p e (d) exists at Migda and a few other farms. 6.7.2.5. The seasonal cycle in the ecosystem. The biological processes in the ecosystem have a characteristic seasonal cycle. There is a well-defined "growing season" from germination after the first effective rains in November or December, until the rapid desiccation of all plants in March--April. Within this period, growth is often continuous; there may be occassional spells of moisture stress in the middle of the period, during which the vegetation stops growing but only rarely dies out. The rate of growth is usually slow in the first two months and very rapid in February and March. Roots grow rapidly and explore effectively all soil layers in which there is moisture, which means down to 30 cm in a dry year to 150 cm in a w e t year. The plants flower mostly in March and set seeds just before soil moisture is exhausted in late March or early April; then seed dispersal occurs. In pastures which are n o t grazed, there is only a slow loss of standing dry vegetation from May, through the dry summer, until October. This loss is mostly through physical erosion and insect activity rather than through microbial decomposition. The latter is activated after the first rains of the next season.

145

Livestock graze the green pasture throughout winter and spring (except possibly for a deferment period just after germination) and the dry pasture in summer and autumn. Crops are harvested in April (barley) and May (wheat). A variable proportion of the straw is gathered and baled shortly after the harvest. The stubble and the ungathered straw may be grazed by livestock during summer, or else burnt or ploughed in.

6.7.3. The nitrogen balance 6.7.3.1. Some characteristic features The treatment of the nitrogen balance is facilitated by some special features of nitrogen processes in semi-arid, winter-rainfall ecosystems with medium-textured soils and annual vegetation. (a) The depth of wetting of the soil profile in most years does n o t exceed the depth which can be effectively utilized by roots ( 8 0 - 1 2 0 cm); thus leaching of nitrogen beyond the root zone is negligible. (b) Conditions which promote rapid denitrification (i.e. low oxygen with high temperatures in the soil) are infrequent. (c) Conditions are relatively favourable for nitrification of ammonium during most of the growing season.(d) Conditions which enhance volatilization of ammonium (high concentration near surface, high temperatures, frequent but superficial wetting) occur only at the end of the growing season (e.g. if there are late spring rains), and in urine patches throughout summer. (e) The main nitrogen inputs to the system are in rain, and fixation by non-symbiotic microorganisms; the amounts of both depend on rainfall a m o u n t and distribution. (f) The organic matter c o n t e n t of the soil is fairly low; the a m o u n t of mineral N released from it each year also depends on rainfall. (g) The potential contribution of symbiotic N-fixation is large compared with the other inputs (rain and non-symbiotic), but the realization of this potential depends on the coincidence of suitable legume and bacteria populations and of soil and climatic conditions suitable for legume growth. (h) In years which are n o t too dry, the annual vegetation, with a dense and growing r o o t system, can take up almost all the nitrate available in the soil, as well as that which becomes available during the growing season. In drought years a surplus of mineral nitrogen may remain in the soil. (i) A large proportion of the annual production of plant biomass and nitrogen can be utilized each year, and is indeed utilized in present management systems. 6.7.3.2. The seasonality o f nitrogen processes Each of the processes in the nitrogen cycle has a definite seasonal pattern, related to the patterns of rainfall, soil moisture and plant growth (Fig. 14). The main nitrogen inputs, rain and non-symbiotic fixation, occur only in the rainy season (November--April) and are distributed within it according to rain events. Rapid decomposition of dead plant remains from the previous season

146

r0n

II

.I.,.I

, J..

soil moisture

temperature

~

plant

green A / " - .

-

biomoss . . d r y

........ s

N inputs (rain* fixation) mineral N

immobilizationmineralization

NH3 volotilizotion

N uptake ( demondl OCT' NOV' C)EC'JAN 'FEB MAR APR 'MAY IJUN IJUL 'AUG I slrp,

Fig. 14. Seasonal patterns of climate, plant growth and nitrogen flows in a semi-arid winter-rainfallecosystem (schematic). (roots; leaves and stalks that have been pressed onto the soil) begins after the first rains in November. But since the C:N ratio of this material is usually higher than the optimum for the decomposing micro-organisms, this pr;)cess may initially not release any mineral nitrogen into the soil (Parnas, 19~5). On the contrary, it may use and immobilize mineral nitrogen, if avail~ ,~le. Later in the wet season, as the C:N ratio decreases and the bacterial L~mass itself begins to decompose, there is net mineralization of nitrogen from the organic remains. A certain proportion of the nitrogen will however remain in the stable organic fraction ("humus"). Uptake of nitrate by plants (or demand for it) begins slowly at germination and accelerates to a very high rate in February and March (Van Keulen, 1975). In this period, any nitrate appearing in the moist root zone may be

147

taken up within days (Van Keulen et al., 1975). Toward the end of March, soil dryness becomes limiting to r o o t activity and plant growth, and the uptake diminishes. In the period of seed filling there is internal redistribution of nitrogen within the plant, from all other organs to the seeds. Fixation by legumes symbionts follows the establishment of the legume plants with a certain lag, and is probably maximal in early spring. Grazing in pastures is yearlong (or almost so). But since the green season is only 3--4 months, most of the material is consumed when dry (in crops -all of the material). For the same reason, most of the nitrogen in excreta returned during the year is n o t likely to be taken up by plants and recycled before the next growing season.

6.7.3.3. Theory of a simple nitrogen balance The special features of the nitrogen cycle in semi-arid ecosystems as described before permit the use, as a first approximation, of a very simple model for calculating the annual nitrogen balance of an ecosystem with annual vegetation and the following attributes (Seligman et al., 1975): (a) no fertilizer or manure input (b) no legumes (c) plant biomass is used by harvesting, n o t by grazing.

IM ~

MY I---~

YO

Fig. 15. A simple model of the annual nitrogen balance in a semi-arid agro-eeosystem: no legumes, no grazing-recycling (see text for definition of symbols).

The following nitrogen pools or compartments are distinguished (Fig. 15). M -- mineral nitrogen in the soil at the end of the growing season H - - n i t r o g e n in stable organic matter ( " h u m u s " ) Y -- nitrogen yield in vegetation at the end of the growing season R -- nitrogen in dead plant residues T -- total nitrogen in the system (M + H + Y + R). The following annual nitrogen flows are considered: IM -- inputs of mineral nitrogen (rain, non-symbiotic fixation) MY -- uptake by plants YO -- nitrogen in plant parts removed by harvest YR -- nitrogen in plant parts left in the system (roots + stubble) RM -- mineral nitrogen released from decomposing plant residues RH -- nitrogen from plant residues incorporated into stable organic matter HM -- mineral nitrogen released from stable organic matter.

148

Some simplifying assumptions are made: (1} The annual nitrogen input is independent of the rest of the system: IM = i. (2) A fraction u of nitrogen in plant biomass is utilized (harvested) each year; the rest is left as residues. (3) A fraction m of nitrogen in plant residues is mineralized rapidly (1--11/~ years); the rest becomes part of the stable organic matter. (4) Nitrogen uptake by plants each year is a fraction f of the available mineral nitrogen, which includes the previous pool (M) plus the inputs during that year (IM + RM + HM). (5) Nitrogen mineralized each year from "humus" is a fraction d of total nitrogen in this material. (6) The mineral nitrogen pool is in equilibrium, and there is no trend towards accumulation or depletion (apart from possible year-to-year fluctuations). (7) The stable organic nitrogen pool is in equilibrium and there is no trend of accumulation or depletion (apart from year-to-year fluctuations). From assumptions 6 and 7 (together with the assumption of complete turnover of Y in one year and of R in 1--2 years) it follows that total nitrogen in the system is also in equilibrium and the input (IM) equals the output (YO). Assumptions 1--3 give the nitrogen conservation equations, assumptions 4--5 the turnover equations and assumptions 6--7 the equilibrium equations. Since the turnover time of stable organic nitrogen is long (of the order of 100 years), assumption 7 and its consequences are true only for a system which has been under the same management for a long time. By combining conservation, equilibrium and turnover equations it is pos,sible to derive explicit expressions (eq. 8--16) for the equilibrium values of all nitrogen pools and annual flows as functions of five parameters: the annual input i; the utilization fraction of plant yield u; the mineralization fraction of plant residues m; the annual mineralization rate of humus d; the utilization fraction of soilmineral nitrogen by the vegetation f. The three latter are more or less biologically determined parameters. The effect of management on the balance is mainly through the utilization u (and potentially through the input i).

Equations for a simple nitrogen balance (no legumes, no grazing recycling) Basic equations (assumptions) Conservation equations IM = i

(I)

Y O = u.MY

(2)

149

Y R = (1-u).MY

5y = 0

RM = m . Y R

(3)

RH = (1-m).YR

AR = 0 AT=M+H+IM-

YO

Turnover equations MY = f (M + IM + HM + RM)

(4)

HM = d . n

(5)

Equilibrium equations IM + HM + RM = MY

AM = 0

(6)

HM = R H

AH = 0

(7)

( t h e r e f o r e IM = YO

A T = 0)

Derived equations (consequences) Flow equations IM = i

(8)

YO = i

(9)

M Y = u1 YR =-

i

1-u

(10)

-i

U

(11)

RM = r e ( l - u ) U

• i

(12)

R H = ( 1 - m ) ( 1 - u) .i

(13)

U

HM = ( 1 - m ) ( 1 - u ) U

•i

(14)

Pool equations M=(T-

1)

H= ( 1 - m ) ( 1 ud

• i

u) . i

(15)

(16)

150

Extension o f N-balance to a livestock system (see Fig. 16 and section 6.7.3.7.) Additional pools are: A = animals F = faeces U = urine Additional flows considered are: YA = nitrogen in vegetation taken up by animals AO = nitrogen removed in animal products AF = nitrogen in faeces from animals AU = nitrogen in urine from animals FO = part o f nitrogen in faeces, leaving the system FR = part o f nitrogen in faeces, which is humified UO = part o f nitrogen in urine leaving the system UM = part o f nitrogen in urine in mineral forms Additional parameters are: x = fraction of consumed N which is r et ur ne d in excret a y = fraction of exc r et a N which occurs in urine v = losses fraction for urine w = losses fraction for faeces Additional equations are: AF = x . A AU = y • A UM = ( 1 - v ) - U FR = ( 1 - w ) - F

l

~UM

~U

V- -I

V-C-1

Fig. 16. A simple model of the annual nitrogen balance in a semi-arid agro-ecosystem with grazing-recycling (no legumes). Nitrogen pools: A, in animals; U, in urine; F, in faeces. Annual nitrogen flows: YA, animal intake; AO, animal products exported; AU, urine excretion; AF, faeces excretion; UO, losses from urine; FO, losses from faeces; UM, from urine to mineral pool; FR, from faeces to fresh organic residues (other symbols - - see text).

6.7.3.4. E x t e n s i v e w h e a t p r o d u c t i o n Classification. All systems considered here have the same climate (200--250 m m rainfall per year), t o p o g r a p h y (plain) and soil t y p e (deep loess); t h e y differ only in management.

151 This section considers management systems in which removal of plant matter is only by direct harvesting and in which no fertilizer is added to the soft, i.e. the extensive grain cropping systems which have existed in the area for thousands of years, until the last decade. For comparison, a non-agricultural (or pre-agricultural) system is also considered, using observations on abandoned cropland. Thus three levels of utilization, u, are considered: Semi-arid non-agricultural (u = 0.2). Reference: Noy-Meir and Harpaz-1; Natural losses by run-off and wildlife, no utilization by man, Table 49. Note: Because there is no agricultural output, this system is an ecosystem, n o t an agro-ecosystem. Extensive grain (u = 0.4). Reference: Noy-Meir and Harpaz-2; Semi-arid wheat area, grain harvested, straw returned, Table 50. Extensive grain (u = 0.6). Reference: Noy-Meir and Harpaz-3, Semi-arid wheat area, grain and straw harvested, Table 50.

Estimation of parameters. A review of data in the literature (Harpaz, 1975) shows that the average concentration of nitrogen in rainwater in semi-arid climates is a b o u t 2 ppm and the average annual input in rain is a b o u t 5 kg ha- 1 (3--8). Reported values of annual fixation by non-symbiotic microorganisms in semi-arid regions vary between 3 and 12 kg ha- 1 ; 5 kg ham a y be taken as a rough average. Thus the annual "natural" nitrogen input to the system is between 5 and 20 kg ha- ' ; in the following calculations an average value of i = 10 kg ha- ~ is assumed. A b o u t 15--20% of the organic matter in plant remains is incorporated into the stable humus; but the nitrogen content of this fraction is a b o u t twice that of the original material. Thus it may be estimated that 30--40% of the nitrogen in residues is incorporated into the humus rather than mineralized rapidly, or m = 0.6--0.7. The annual rate of mineralization of the stable organic nitrogen: in this ecosystem is relatively low, because the soil is wet for only about 100 days each year, and this in the coolest months. The average annual rate is estimated at 0.2%, i.e. d = 0.002. If growth is limited by nitrogen, it may be assumed that the dense r o o t system of the annual vegetation is capable of extracting almost all (f --- 0.9-1.0) mineral nitrogen in the r o o t zone during the growing season.

Effect of utilization. As explained, the difference between the three systems is the utilization u. By applying the nitrogen balance equations it can be seen that the level of utilization has marked effects on the equilibrium levels of nitrogen flows and on the productivity of the system (Table 48). At high utilization, the nitrogen and dry matter production axe reduced considerably. The harvested nitrogen yield YO is unchanged, but since at u = 0.4 it is all in grain and at u = 0.6 it includes grain and straw, the grain yield is lower at u = 0.6. The utilization level also has a drastic influence on the equilibrium level of stable organic nitrogen.

152 TABLE 48 The annual nitrogen balance of a simple agro-ecosystem (no legumes, no recycling, no fertilizer) in a semi-arid climate: calculated equilibrium levels at different levels of plant biomass utilization u Other parameters i -- 10 kg N ha -~ , m = 0.6, f = 0.9, d = 0.002

Utilization u

Ref. Noy-Meir and Harpaz-1

Ref. Noy-Meir Ref. Noy-Mei and Harpaz-2 and Harpaz-3

0.2

0.4

Nitrogen flows (kg N ha -~ y-~ ) IM 10 MY 50 YO 10 YR 40 RM 24 RH 16 I-IM 16 Nitrogen pools (kg N ha -~ ) M 5.6 H 8000 Total available N = M + IM + RM + HM 55.6 Biomass production (1% N) (kg dry matter ha -~ ) 5000 Harvested yields (kg dry matter ha -1 ) Grain (1.5% N) 0 Straw (0.75% N) 0

10 25 10 15 9 6 6

0.6 10 16.7 10 6.7 4 2.7 2.7

2.7 3000

1.8 1350

27.7 2500

18.5 1667

667 0

444 444

I n T a b l e 4 8 n i t r o g e n yields have been used also t o calculate biomass pro-~ d u c t i o n , harvested grain and harvested straw, assuming t h a t the N c o n c e n t r a t i o n in d r y m a t t e r is 1% in t o t a l biomass, 1.5% in grain a n d 0.75% in straw. T h e grain yields thus c a l c u l a t e d ( 4 0 0 - - 7 0 0 kg h a - 1 ) are similar in m a g n i t u d e t o t h o s e actually o b t a i n e d in unfertilized w h e a t and barley fields in t h e B e d o u i n a g r o - e c o s y s t e m in the Negev ( 4 0 0 - - 8 0 0 kg h a - 1 ), in years w h i c h are n o t d r o u g h t y e a r s (/> 2 0 0 m m rain).

6.7.3.5. Water or nitrogen limitation So far calculations have been based o n the a s s u m p t i o n t h a t a n n u a l nitrogen u p t a k e a n d p l a n t p r o d u c t i o n are limited, a n d d e t e r m i n e d b y t h e s u p p l y o f available n i t r o g e n , and n o t b y o t h e r factors, such as w a t e r s u p p l y . I t m a y be q u e s t i o n e d w h e t h e r this a s s u m p t i o n is still r e a s o n a b l e in semi-arid climates. T h e c o m b i n e d effects o f w a t e r and n i t r o g e n s u p p l y o n p l a n t p r o d u c t i o n can be a p p r o x i m a t e d b y Liebig's law o f the m i n i m u m (Shimshi, 1971). T h u s it is necessary t o c o m p a r e the n i t r o g e n u p t a k e MY N calculated f r o m the n i t r o g e n balance as above, and c o n s e q u e n t biomass p r o d u c t i o n YN, with the

153 biomass production calculated from the annual water supply to the crop, assuming unlimited nitrogen: Yw=eT=e(R-E)

(17)

and the nitrogen uptake demanded by it: MY w = cY w

= ce (R - E)

(18)

where: subscript N refers to limitation by nitrogen and subscript w refers to limitation by water T = annual water uptake (transpiration) by vegetation (mm) R = annual rainfall E = annual water loss by direct evaporation from soil e = ratio of biomass production to water consumption ("water use efficiency") in conditions of abundant nitrogen (kg ha- J / mm) c = nitrogen content of biomass in the same conditions. If MY N is less than MY w (and YN < Yw), production and N-uptake are limited mainly by the nitrogen supply, and MY may be assumed to be equal to MY N, as was done in Table 48. But if MY w is less than MY N (and Yw < YN ), as may happen when rainfall is sufficiently low, production is limited mainly by the water supply. In this case MY will be close to MYw, i.e. less than calculated from the nitrogen balance equations. The production:transpiration ratio e depends on climatic conditions during the growing season. In a winter-rainfall climate such as at Migda, it is a b o u t 50 kg ha- 1 of total biomass per mm, when nitrogen is abundant (Van Keulen, 1975). The final nitrogen content of biomass in these conditions is a b o u t 1.2% (Shimshi, 1971; Harpaz, 1975). Thus, for every mm of water available for transpiration, a b o u t 0.6 kg ha- 1 of nitrogen needs to be available for uptake to ensure that nitrogen is n o t limiting. Taking the values of MY in Table 48, it can be seen that at the low utilization level, nitrogen is expected to become limiting even when the water supply exceeds 80 mm; at medium and high utilization, the expected threshold is even lower. The partition of water input between transpiration and evaporation depends on rainfall distribution within the season, and n o t only on total rainfall. But as a general trend, as R increases the absolute amount of evaporation increases, but its relative proportion decreases. Thus T is a concave function of R, which may be approximated by a linear relation above a threshold R t : T = b (R - R t )

(19)

with scatter around this line due to variation in distribution. The water-limited production and N-uptake will be a similar function of rainfall (Fig. 17). If the nitrogen-limited production and uptake were inde-

154

T A B L E 49 S y s t e m t y p e : Semi-arid, non-agricultural

S u m m a r y of n u t r i e n t flows (units: kg h a -1 y - i )

T y p e o f f a r m or e c o s y s t e m or t y p e o f part o f a f a r m or e c o s y s t e m , ref. no. Noy-Meir and Harpaz-1

Wildlife on semi-arid Israelian p a s t u r e no utilization b y m a n .

Nutrient

N

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

29. 30t. 30r. 31.

I n p u t b y seeds or seedlings . . . . . . . . . . . . . . . T r a n s f e r b y n e t u p t a k e f r o m soil . . . . . . . . . . . T r a n s f e r b y n e t u p t a k e f r o m soil . . . . . . . . . . . Input by uptake from atmosphere . . . . . . . . . .

-} 50 -50

TOTAL REMOVALS:

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . T r a n s f e r b y grazing o f forage . . . . . . . . . . . . . Output by primary products . . . . . . . . . . . . . . T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g on field . T r a n s f e r b y seed for s o w i n g . . . . . . . . . . . . . . TOTAL

-pm -50 -50

SUPPLIES-REMOVALS

0

Changes in a m o u n t o f animal c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4.

I n p u t b y feed for livestock . . . . . . . . . . . . . . . I n p u t b y litter used indoors . . . . . . . . . . . . . . T r a n s f e r b y c o n s u m p t i o n o f h a r v e s t e d crops T r a n s f e r b y grazing o f forage . . . . . . . . . . . . . TOTAL

5. 6.

O u t p u t by a n i m a l p r o d u c t s . . . . . . . . . . . . . . . Outp.ut b y losses f r o m m a n u r e t o air, b e f o r e application . . . . . . . . . . . . . . . . . . . . . . . . . Output by manure . . . . . . . . . . . . . . . . . . . . Transfer by application of manure and/or waste . T r a n s f e r b y droppings o n g r a z e d areas . . . . . . . TOTAL

. • 9.

-. . . pm 0 --pm 0

SUPPLIES-REMOVALS

0

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

T r a n s f e r by application o f m a n u r e a n d / o r waste . T r a n s f e r b y d r o p p i n g s on grazed areas . . . . . . . Input by application of manure . . . . . . . . . . . . I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . I n p u t b y N-fixation . . . . . . . . . . . . . . . . . . . . I n p u t b y a p p l i c a t i o n o f litter, sludge and w a s t e . I n p u t b y irrigation a n d flooding • • ~ . . . . . . . . I n p u t b y d r y and w e t deposition . . . . . . . . . . . T r a n s f e r b y p l a n t p r o d u c t s r e m a i n i n g on field . . T r a n s f e r b y seed for sowing' . . . . . . . . . . . . . . TOTAL

----

R E M O V A L S : 19. 20. 21. 22. 23. 28. 30.

O u t p u t by denitrification . . . . . . . . . . . . . . . . O u t p u t by vblatilization o f a m m o n i a . . . . . . . . O u t p u t b y leaching . . . . . . . . . . . . . . . . . . . . O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . O u t p u t b y dust . . . . . . . . . . . . . . . . . . . . . . O u t p u t by organic m a t t e r , r e m o v e d b y r u n - o f f * . T r a n s f e r by n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL

Changes in a m o u n t o f total soil c o m p o n e n t SUPPLIES:

SUPPLIES-REMOVALS • and wind erosion

5 0 5 45 -55 t t 0 t t 5 50 55 0

155

TABLE 49 (continued) S y s t e m t y p e : Semi-arid, n o n - a g r i c u l t u r a l

Summary of n u t r i e n t flows (units: k g h a -~ ~ - I )

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , r e f . n o . N o y - M e i r a n d I-Iarpaz-1

Wildlife o n semi-arid Israelian p a s t u r e , no utilization by man.

Nutrient

N

C h a n g e s in a m o u n t o f available soil n u t r i e n t s SUPPLIES:

REMOVALS:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s o n grazed areas . . . . . . . Input by application of manure ............ I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . Input by N-fixation .................... I n p u t b y a p p l i c a t i o n o f litter, sludge a n d w a s t e . Input by im'gation and flooding ........... Input by dry and wet deposition ........... T r a n s f e r b y w e a t h e r i n g o f soil m i n e r a l f r a c t i o n . . T r a n s f e r b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g o n field . T r a n s f e r b y seed f o r s o w i n g . . . . . . . . . . . . . . TOTAL

19. 20. 21. 22. 23. 24. 25. 30t. 3Or.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . Output by dust ...................... T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n Transfer by net uptake by the plant Transfer by net uptake by the plant i:::::~:} TOTAL SUPPLIES-REMOVALS

-pm --5 O 5 -16 24 t 50 t t 0 t t -0 50 50 0

Changes in a m o u n t of soil organic matter SUPPLIES:

REMOVALS:

8b. 9b. lOb. 13b. 25. 26b.

Transfer Transfer Input by Input by Transfer Transfer

by application and/or waste . . . . . . . . by droppings on grazed areas . . . . . . . application of m a n u r e . . . . . . . . . . . . application of litter,sludge and waste . by immobilization in soil organic fraction by plant products remaining on field . . TOTAL

17. 28.

T r a n s f e r b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n Output by organic matter, removed by run-off.. TOTAL SUPPLIES-REMOVALS

-pm

16+5 16+5 16 5 16+5 O

C h a n g e s in a m o u n t o f soil m i n e r a l s SUPPLY: REMOVAL:

24. 16.

T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y w e a t h e r i n g o f soil f r a c t i o n . . . . : . . SUPPLY- REMOVAL

---

156

T A B L E 50 S y s t e m t y p e : Extensive grain T y p e of f a r m or e c o s y s t e m or t y p e o f p a r t o f a f a r m or e c o s y s t e m , ref. no. Noy-Meir and H a r p a z - 2 + 3

S u m m a r y of n u t r i e n t flows (units: kg ha -~ y - i ) Wheat, semi-arid area, s y s t e m - 2 : grain h a r v e s t e d , s t r a w r e t u r n e d ; system-3 : grain+ s t r a w harvested.

Nutrient

System-2 N

System-3 N

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES :

REMOVALS:

29. 30t. 30r. 31.

I n p u t b y seeds or seedlings . . . . . . . . . . . . . . . T r a n s f e r b y n e t u p t a k e f r o m soil . . . . . . . . . . . T r a n s f e r b y n e t u p t a k e f r o m soil . . . . . . . . . . . Input by uptake from atmosphere . . . . . . . . . . TOTAL

t • ~ 25 -25

3. 4. 18. 26. 27.

T r a n s f e r by c o n s u m p t i o n o f h a r v e s t e d crops . . . T r a n s f e r by grazing o f forage . . . . . . . . . . . . . Output by primary products . . . . . . . . . . . . . . T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g on field . T r a n s f e r by seed for s o w i n g . . . . . . . . . . . . . . TOTAL

t 17 17

-1-0 15 t 25

-10 7 t 17

0

0

SUPPLIES-REMOVALS Changes in a m o u n t o f a n i m a l c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4.

Input by Input by Transfer Transfer

5. 6.

Output by animal products . . . . . . . . . . . . . . . O u t p u t b y losses f r o m m a n u r e to air, b e f o r e application . . . . . . . . . . . . . . . . . . . . . . . . . Output by manure . . . . . . . . . . . . . . . . . . . . T r a n s f e r b y application o f m a n u r e a n d / o r w a s t e . T r a n s f e r b y d r o p p i n g s on grazed areas . . . . . . . TOTAL

7. 8. 9.

feed for livestock . . . . . . . . . . . . . . . litter used i n d o o r s . . . . . . . . . . . . . . by consumption of harvested crops b y grazing o f forage . . . . . . . . . . . . . TOTAL

.

.

----

.

-------

SUPPLIES-REMOVALS Changes in a m o u n t o f total soil c o m p o n e n t SUPPLIES :

8. 9

101 11. 12. 13. 14. 15. 26. 27. R E M O V A L S : 19. 20. 21. 22. 23. 28. 30.

Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s on grazed areas . . . . . . . I n p u t b y application o f m a n u r e . . . . . . . . . . . . I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . I n p u t b y N-fixation . . . . . . . . . . . . . . . . . . . . I n p u t b y application o f litter, sludge and w a s t e . I n p u t b y irrigation and flooding . . . . . . . . . . . I n p u t b y d r y and w e t d e p o s i t i o n . . . . . . . . . . . T r a n s f e r b y p l a n t p r o d u c t s r e m a i n i n g on field . . T r a n s f e r b y seed for s o w i n g . . . . . . . . . . . . . . TOTAL O u t p u t b y denitrification . . . . . . . . . . . . . . . . O u t p u t b y volatilization o f a m m o n i a . . . . . . . . O u t p u t by leaching . . . . . . . . . . . . . . . . . . . . O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . O u t p u t b y dust . . . . . . . . . . . . . . . . . . . . . . O u t p u t b y organic m a t t e r , r e m o v e d b y r u n - o f f . . T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL SUPPLIES-REMOVALS

----5

5 --

-5 7

5 15 t 25

t 17

t t

t t

0 --

0

t t 25 25

t t 17 17

0

0

157

TABLE

50 (continued)

System type:Extensive grain

S u m m a r y of nutrient flows (units: kg ha -l 'y-1 )

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no. Noy-Meir and Harpaz-2 + 3

Wheat, semi-arid area, system-2; grain harvested, straw returned. System-3; grain + straw harvested System-2 System -3 N N

Nutrient Changes in amount of available soil nutrients SUPPLIES:

8a. T r a n s f e r b y a p p l i c a t i o n o f m a n u r e a n d / o r waste . 9a. T r a n s f e r b y d r o p p i n g s on grazed areas . . . . . . . 10a. I n p u t b y a p p l i c a t i o n o f m a n u r e . . . . . . . . . . . .

---

11.

Input by fertilizers . . . . . . . . . . . . . . . . . . . .

--

12. 13a. 14. 15. 16. 17. 26a. 27.

I n p u t b y N-fixation . . . . . . . . . . . . . . . . . . . . I n p u t b y a p p l i c a t i o n o f litter, sludge a n d w a s t e . I n p u t b y irrigation and flooding . . . . . . . . . . . I n p u t b y dry and w e t d e p o s i t i o n . . . . . . . . . . . T r a n s f e r b y w e a t h e r i n g o f soil m i n e r a l f r a c t i o n . . T r a n s f e r b y m i n e r a l i z a t i o n o f soil organic fraction T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g on field . T r a n s f e r b y seed for s o w i n g . . . . . . . . . . . . . . TOTAL

5 --

R E M O V A L S : 19. 20. 21. 22. 23. 24. 25. 30t. 30r.

Output by denitrification . . . . . . . . . . . . . . . . O u t p u t b y volatilization o f a m m o n i a . . . . . . . . O u t p u t b y leaching . . . . . . . . . . . . . . . . . . . . O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . O u t p u t b y dust . . . . . . . . . . . . . . . . . . . . . . T r a n s f e r b y fixation in soil m i n e r a l fraction . . . . T r a n s f e r b y i m m o b i l i z a t i o n in soil organic fraction Transfer by net uptake by the plant . . . . . . . . . T r a n s f e r b y n e t u p t a k e b y the p l a n t TOTAL ......... SUPPLIES-REMOVALS

--

5 -6 9 ~

5 -5 3 4 17

~ ------25

17

~

17 0

0

Changes in a m o u n t o f soil organic m a t t e r SUPPLIES:

8b. 9b. 10b. 13b. 25. 26b.

Transfer Transfer Input by Input by Transfer Transfer

by application and/or waste . . . . . . . . b y droppings on grazed areas . . . . . . . application of m a n u r e . . . . . . . . . . . . a p p l i c a t i o n o f litter, sludge and w a s t e . b y i m m o b i l i z a t i o n in soil organic f r a c t i o n b y . p l a n t p r o d u c t s r e m a i n i n g on field . .

TOTAL R E M O V A L S : 17. 28.

T r a n s f e r b y m i n e r a l i z a t i o n o f soil organic fraction O u t p u t b y organic m a t t e r , r e m o v e d b y r u n - o f f . . TOTAL SUPPLIES-REMOVAI_,S

-----6

3

6

3

6 -6

3

0

0

Changes in a m o u n t o f soil minerals SUPPLY: REMOVAL:

24. 16.

T r a n s f e r b y fixation in soil m i n e r a l fraction . . . . T r a n s f e r b y w e a t h e r i n g o f soil fraction . . . . . . . SUPPLY- REMOVAL

---

3

158

4000

//

t

/

3000

~"~// - J ....

~ 2000 .-~,.

6

//

~'~°~'t;" /./

/

~

/

~

~ooo //

0(~

__ ,,~'F-

j

100

Fig. 17. Nitrogen-limited,

I

200 Rainfall (ram)

I

300

4~30

water-limited and actual yields o f plant biomass as functions o f

total annual rainfall (schematic, disregarding effects of rainfall distribution).

pendent of rainfall, they could be represented by a horizontal line. Its intersection with the MY w = f(R) would give the rainfall threshold above which nitrogen rather than water becomes limiting. Yield would increase with rainfall up to this threshold and remain constant above it. However, in semi-arid zones, many of the processes which supply mineral nitrogen to the soil are themselves dependent on the a m o u n t and distribution of rainfall: nitrogen input in rain, nitrogen fixation, mineralization of N from both fresh and stable organic matter. Therefore MY N (and YN) will also be an increasing function of annual rainfall R (+ scatter due to distribution). It may be expected to be an initially convex function, because even at rather low rainfall some mineral nitrogen is available. At a higher rainfall it is expected to become less steep than the MY w function and to intersect it. At the intersection, nitrogen becomes limiting. Simulations using detailed meteorological data (Harpaz, 1975) indicate that this intersection, in the conditions of Migda, is around 200 mm annual rainfall (between 150 and 250 mm, depending on distribution). An interesting corollary is that in the range of 200--400 mm, yields in unfertilized agro-ecosystems are expected to increase with rainfall, even though nitrogen rather than water is the main limiting factor. This response is due to the influence of rainfall on nitrogen inputs, and its slope will n o t be as steep as the "direct" response of yield to rainfall, in the same range, systems with abundant nitrogen fertilization.

159

6.7.3.6. The effects of rainfall variability If the amount and distribution of rain were constant between years, each a g r o - e c o s y s t e m c o u l d b e c h a r a c t e r i z e d as e i t h e r n i t r o g e n - l i m i t e d o r w a t e r l i m i t e d i n all y e a r s . I n t h e f i r s t case, p r a c t i c a l l y all m i n e r a l n i t r o g e n w o u l d b e u s e d u p e v e r y d a y . I n t h e s e c o n d case, t h e r e w o u l d b e a s u r p l u s e v e r y y e a r a n d m i n e r a l n i t r o g e n w o u l d b e e x p e c t e d t o a c c u m u l a t e i n t h e soil. H o w e v e r , s e m i - a r i d c l i m a t e s are c h a r a c t e r i z e d b y l a r g e v a r i a b i l i t y i n p r e c i p i t a t i o n . T h u s i n a n y g i v e n s y s t e m , p l a n t p r o d u c t i o n will b e l i m i t e d b y water in some years ("drought") and by nitrogen in others ("wet"). The

TABLE 51 Comparison between the annual nitrogen balance calculated at equilibrium for a semiarid agro~ecosystem (no legumes, no fertilizer) with two management systems in which utilization is (a) by direct harvesting, (b) by grazing with recycling of excreta; both at medium utilization, u = 0.4. Other parameters: i = 10 kg N h a - ' , m = 0.6, f = 0.9, d = 0.002, x = 0.9, y = 0.7, v = 0.6, w = 0.6 (x, fraction of consumed N which is returned in excreta; y, fraction of excreta N which occurs in urine; v, losses fraction for urine; w, losses fraction for faeces) Ref. Noy-Meir and Harpaz-2, harvesting Nitrogen flows (kg N h a - ' y - ' ) IM MY YO or YA YR RM RH HM AO AU AF UO FO UM FR Nitrogen pools (kg N y - ' )

10 25 10 15 9 6 6

Harvested yields (kg ha -~ ) Grain (1.5% N) Animal live weight (3%N)

10 39 15.6 23.3 15 10 10 1.6 9.8 4.2 5.9 2.5 3.9 1.7

--------

M

H Total available = M + I M + RM +HM +UM Biomass production (1% N) (kg d.m. h a - ' ) Utilized biomass (kg d.m. h a - ' )

Ref. Noy-Meir and Harpaz-4, grazing

2.7

4

3000

5000

27.7 2500

43 3900

667 (grain)

1560 (pasture)

667 --

-53

160

T A B L E 52 S y s t e m t y p e : Extensive livestock

Summary of n u t r i e n t flows (units: kg h a - ' y - t )

T y p e o f farm or e c o s y s t e m or t y p e o f p a r t o f a f a r m or e c o s y s t e m , ref. no. Noy-Meir and Harpaz-4

S h e e p on semi-arid Israelian pastures, production of meat

Nutrient

N

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

REMOVALS:

29. 30t. 30r. 31.

I n p u t by seeds or seedlings . . . . . . . . . . . . . . . T r a n s f e r b y n e t u p t a k e f r o m soil . . . . . . . . . . . T r a n s f e r b y n e t u p t a k e f r o m soil . . . . . . . . . . . Input by uptake from atmosphere . . . . . . . . . . TOTAL

--

3. 4. 18. 26. 27.

T r a n s f e r by c o n s u m p t i o n o f h a r v e s t e d c r o p s . . . T r a n s f e r by grazing o f forage . . . . . . . . . . . . . O u t p u t by p r i m a r y p r o d u c t s . . . . . . . . . . . . . . T r a n s f e r by p l a n t p r o d u c t i o n r e m a i n i n g on field . T r a n s f e r b y seed for sowing T O T A. .L. . . . . . . . . . . .

i J

39 -39 -16 -23 39

SUPPLIES-REMOVALS

0

Changes in a m o u n t o f animal c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4.

I n p u t by feed for livestock . . . . . '. . . . . . . . . . I n p u t b y litter used indoors . . . . . . . . . . . . . . T r a n s f e r by c o n s u m p t i o n o f harvested crops T r a n s f e r b y grazing of forage . . . . . . . . . . . . . TOTAL

5. 6.

O u t p u t by animal p r o d u c t s . . . . . . . . . . . . . . . O u t p u t by losses f r o m m a n u r e to air, b e f o r e application . . . . . . . . . . . . . . . . . . . . . . . . . O u t p u t by m a n u r e . . . . . . . . . . . . . . . . . . . . . T r a n s f e r by application o f m a n u r e a n d / o r waste . T r a n s f e r b y droppings on g r a z e d areas . . . . . . . TOTAL

7. 8. 9.

--. . . 1-6 16 2 8 -6 16

SUPPLIES-REMOVALS

0

T r a n s f e r by application o f m a n u r e a n d / o r waste . T r a n s f e r by droppings on grazed areas . . . . . . . Input by application of manure . . . . . . . . . . . . I n p u t by fertilizers . . . . . . . . . . . . . . . . . . . . I n p u t by N-fixation . . . . . . . . . . . . . . . . . . . . I n p d t by application o f litter, sludge and w a s t e . I n p u t by irrigation and flooding . . . . . . . . . . . I n p u t b y d r y and w e t d e p o s i t i o n . . . . . . . . . . . T r a n s f e r by p l a n t p r o d u c t s r e m a i n i n g on field . . T r a n s f e r by seed for s o w i n g . . . . . . . . . . . . . . TOTAL

-6 --

Changes in a m o u n t o f total soil c o m p o n e n t SUPPLIES:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

R E M O V A L S : 19. 20. 21. 22. 23. 28. 30.

5 --5 23 -39

O u t p u t b y denitrification . . . . . . . . . . . . . . . . . O u t p u t b~/volatilization o f a m m o n i a . . . . . . . . O u t p u t b y leaching . . . . . . . . . . . . . . . . . . . . O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . O u t p u t by dust . . . . . . . . . . . . . . . . . . . . . . O u t p u t by organic m a t t e r , r e m o v e d b y r u n - o f f . , T r a n s f e r by n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL

t t 0 t t t 39 39

SUPPLIES-REMOVALS

0

161

T A B L E 52 ( c o n t i n u e d ) S y s t e m t y p e : E x t e n s i v e livestock

S u m m a r y of n u t r i e n t flowS (units: kg h a -1 y - i )

Type of farm or ecosystem or type of part of a f a r m or e c o s y s t e m , ref. no. Noy-Meir and Harpaz-4

S h e e p on semi-arid Israelian pastures, production of meat

Nutrient

N

Changes in a m o u n t o f available soil n u t r i e n t s SUPPLIES:

8a. 9a.

Transfer by application of m a n u r e and/or waste . T r a n s f e r b y d r o p p i n g s on grazed areas . . . . . . .

10a. I n p u t b y a p p l i c a t i o n o f m a n u r e . . . . . . . . . . . . 11. 12. 13a. 14. 15. 16. 17. 26a. 27. R E M O V A L S : 19. 20. 21. 22. 23. 24. 25. 30t. 30r.

I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . I n p u t b y N-fixation . . . . . . . . . . . . . . . . . . . . I n p u t b y a p p l i c a t i o n o f litter, sludge and w a s t e . I n p u t b y irrigation and flooding . . . . . . . . . . . I n p u t by dry and wet deposition . . . . . . . . . . . T r a n s f e r b y w e a t h e r i n g o f soil m i n e r a l f r a c t i o n . . T r a n s f e r b y m i n e r a l i z a t i o n o f soil organic fraction T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g on field . T r a n s f e r by seed for s o w i n g . . . . . . . . . . . . . . TOTAL O u t p u t by denitrification . . . . . . . . . . . . . . . . O u t p u t b y volatilization o f a m m o n i a . . . . . . . . O u t p u t b y leaching . . . . . . . . . . . . . . . . . . . . O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . Output by dust . . . . . . . . . . . . . . . . . . . . . . T r a n s f e r b y fixation in soil m i n e r a l fraction . . . . T r a n s f e r b y i m m o b i l i z a t i o n in soil organic fraction T r a n s f e r b y n e t u p t a k e b y the p l a n t . . . . . . . . . Transfer by net uptake ~ O ~ l a n t

-4 --5 -5 --10 15 39 ------39

SUPPLIES-REMOVALS

0

Changes in a m o u n t o f soil organic m a t t e r SUPPLIES:

8b. 9b. 10b. 13b. 25. 26b.

R E M O V A L S : 17. 28.

Changes SUPPLY: REMOVAL:

in a m o u n t 24. 16.

Transfer by application and/or waste . . . . . . . . T r a n s f e r b y d r o p p i n g s on grazed areas . . . . . . . Input by application of manure . . . . . . . . . . . . I n p u t b y a p p l i c a t i o n o f litter, sludge a n d w a s t e . T r a n s f e r b y i m m o b i l i z a t i o n in soil organic fraction T r a n s f e r b y p l a n t p r o d u c t s r e m a i n i n g on field . . TOTAL

2 ---8 10

T r a n s f e r b y m i n e r a l i z a t i o n o f soil organic fraction O u t p u t by organic m a t t e r , r e m o v e d b y r u n - o f f . . TOTAL

10 -10

SUPPLIES-REMOVALS

0

Transfer b y fixation in soil mineral fraction . . . . Transfer b y weathering of soil fraction . r . . . . .

---

of soil minerals

SUPPLY-REMOVAL

162

mineral nitrogen left unused in the soil in a drought will mostly be available for use, and will be actually taken up, in subsequent rainy (N-limited) years. The frequency of the two types of year is of course related to the average annual rainfall. In the conditions of Migda (average 250 mm) simulation results indicated that of 12 years, 6 were water-limited and 6 nitrogenlimited (Van Keulen, 1975; Harpaz, 1975). Even at the dry end of the semiarid region (average 150 mm) there are occasionally years with 250 mm or more, in which nitrogen is expected to become limiting because the mineral nitrogen that has accumulated in the soil is exhausted. The size of the mineral N pool will thus never be at equilibrium, b u t will fluctuate according to yearly rainfall conditions. All other components of the nitrogen balance will fluctuate similarly around their equilibrium values. This dynamic situation has several consequences: for instance, yield is expected to be higher in a rainy year that follows a drought (due to carryover of surplus N) than in a rainy year that follows a rainy year.

6. 7.3.7. Livestock systems Classification. Extensive livestock. Reference: Noy-Meir and Harpaz-4; Sheep on semi-arid Israelian pastures, production of meat, Table 52. The calculations in Table 51 were based on the assumption that the utiliz ed part of the annual vegetation was harvested in such a way that all its nitrogen was exported from the system. This section considers a system in which the utilized production is "harvested" by a population of herbivores (e.g. sheep) which remains in the pasture for most of the year (Fig. 16). Part of the nitrogen in utilized biomass is returned to the soil in animal excreta. Several equations in the annual balance have to be added or modified to account for this. Only a small proportion (5--15%) of consumed plant nitrogen is retained by the animals and exported as secondary production, b u t a considerable proportion of N in excreta is n o t really recycled to the soil--pasture system for various reasons: (a) part accumulates in stock camping areas rather than being spread over the pasture; (b) much of the nitrogen remains near the surface and volatilizes during dry periods, before being leached into the root zone; and (c) nitrogen in dry faeces on the soil surface is exposed to volatilization and to erosion for long periods before being leached in. After accounting for these losses, there is still a substantial proportion (20--40%) of the nitrogen in excreta which is effectively recycled into the r o o t zone and is available for plant uptake in the following growing season (or to some extent, inthe same one). Urine nitrogen becomes available as mineral nitrogen within a few weeks. Faeces nitrogen becomes in part available as mineral N during decomposition, and in part is incorporated into the stable organic matter.

,

4400* --

667 --

185

27.7

16600*

19 3000 + 34

2.7 3000 0

2500

100 166 66 100 60 40 6

0.4

10 25 10 15 9 6 6

0.4

Ref. N o y - M e i r a n d Harpaz-5, w i t h fertilizers

P o t e n t i a l yield, realized o n l y w h e n w a t e r is n o t limiting.

N i t r o g e n flows (kg N h a - ' y-~ ) IM MY YO YR RM RH HM N i t r o g e n p o o l s (kg N h a -~ ) M H AH (annual) T o t a l available N M + IM + RM + HM Biomass p r o d u c t i o n (kg d.m. h a - I ) H a r v e s t e d yields (kg d.m. h a -1 ) Grain Straw

Utilization u

Ref. N o y - M e i r a n d Harpaz-2 --

444 444

1667

18.5

1.8 1350 0

10 16.7 10 6.7 4 2.7 2.7

0.6

Ref. N o y - M e i r a n d Harpaz-3 --

3550* 3550*

13500*

150

15 1350 + 19.3

100 135 81 54 32 22 2.7

0.6

Ref. N o y - M e i r a n d Harpaz-6, w i t h fertilizers

T h e initial e f f e c t o f a d d i n g N fertilizer a t 9 0 kg N h a -1 y - 1 t o a s i m p l e a g r o - e c o s y s t e m ( n o legumes, n o grazing-recycling), c a l c u l a t e d a t t w o levels o f u t i l i z a t i o n . I t is a s s u m e d t h a t t h e m i n e r a l N p o o l has a l r e a d y r e a c h e d e q u i l i b r i u m w i t h t h e n e w i n p u t , b u t t h e h u m u s N is still at t h e o l d level, i = 10 + 9 0 = 1 0 0 kg h a -~ y - ~ . O t h e r p a r a m e t e r s as in T a b l e 51

T A B L E 53

O~

164

T A B L E 54 S y s t e m t y p e : Intensive grain

S u m m a r y of n u t r i e n t flows (units: kg ha - I y - i )

T y p e of f a r m or e c o s y s t e m or t y p e o f p a r t of a f a r m o r e c o s y s t e m , ref. no. Noy-Meir and H a r p a z - 5 + 6

Intensive Israelian arable f a r m . semi-arid area, System-5: grain h a r v e s t e d , s t r a w r e t u r n e d S y s t e m - 6 : grain + s t r a w h a r v e s t e d

Nutrient

System-5 N

Syatem-6 N

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

REMOVALS:

29. 30t. 30r. 31. 3. 4. 18. 26. 27.

I n p u t b y seeds or seedlings . . . . . . . . . . . . . . . T r a n s f e r b y n e t u p t a k e f r o m soil . . . . . . . . . . . T r a n s f e r by n e t u p t a k e f r o m soil . . . . . . . . . . . Input by uptake from atmosphere . . . . . . . . . . TOTAL

j

T r a n s f e r b y c o n s u m p t i o n of h a r v e s t e d crops . . . T r a n s f e r b y grazing o f forage . . . . . . . . . . . . . Output by primary products . . . . . . . . . . . . . . T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g on field . T r a n s f e r b y seed for s o w i n g . . . . . . . . . . . . . . TOTAL

t

t

166 -166

135 135

--81 54

66 100 t 166

t 135

0

0

SUPPLIES-REMOVALS Changes in a m o u n t o f animal c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4.

I n p u t b y feed" for livestock . . . . . . . . . . . . . . . I n p u t by litter used indoors . . . . . . . . . . . . . . Transfer by consumption of harvested crops T r a n s f e r by grazing o f f ~ O ~ A L . . . . . . . . . . . .

. . .

---

5. 6.

O u t p u t by animal p r o d u c t s . . . . . . . . . . . . . . . Out~.ut b y losses f r o m m a n u r e to air, b e f o r e application . . . . . . . . . . . . . . . . . . . . . . . . . Output by manure . . . . ................ T r a n s f e r b y application o f m a n u r e a n d / o r w a s t e . T r a n s f e r b y droppings on grazed areas . . . . . . . TOTAL

--

7. 8. 9.

---

----

SUPPLIES-REMOVALS Changes in a m o u n t o f total soil c o m p o n e n t SUPPLIES:

8. T r a n s f e r by application o f m a n u r e a n d / o r w a s t e . 19"0. T r a n s f e r b y droppings on grazed areas . . . . . . . I n p u t b y application o f m a n u r e . . . . . . . . . . . . 11. I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . 12. I n p u t b y N-fixation . . . . . . . . . . . . . . . . . . . . 13. I n p u t b y application o f litter, sludge and waste . 14. I n p u t b y irrigation and flooding . . . . . . . . . . . 15. Input by dry and wet deposition . . . . . . . . . . . 26. T r a n s f e r b y p l a n t p r o d u c t s r e m a i n i n g on field . . 27. T r a n s f e r b y seed for s o w i n g . . . . . . . . . . . . . . TOTAL

R E M O V A L S : 19. 20. 21. 22. 23. 28. 30.

O u t p u t b y denitrification . . . . . . . . . . . . . . . . O u t p u t b y volatilization o f a m m o n i a . . . . . . . . O u t p u t b y leaching . . . . . . . . . . . . . . . . . . . . O u t p u t by r u n - o f f o f available n u t r i e n t s . . . . . . O u t p u t b y dust . . . . . . . . . . . . . . . . . . . . . . O u t p u t b y organic m a t t e r , r e m o v e d b y r u n - o f f T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL

---90 5

90 5 --

-5 54

1050 20--0 t t

154 t t

0 .

SUPPLIES-REMOVALS

.

0

t t

t t

t

t

166 166

135 135

+34

+19

165

T A B L E 54 ( c o n t i n u e d ) S y s t e m t y p e : Intensive grain T y p e o f f a r m or e c o s y s t e m or t y p e o f p a r t o f a f a r m o r e c o s y s t e m , ref. no. Noy-Meir and H a r p a z - 5 + 6

S u m m a r y of n u t r i e n t flows (units: kg h a -~ y - i ) Intensive lsraelian arable f a r m , semi-arid area S y s t e m - 5 ; grain h a r v e s t e d , s t r a w r e t u r n e d S y s t e m - 6 ; grain + s t r a w h a r v e s t e d

Nutrient

System-5 N

System-6 N

Changes in a m o u n t o f available soil n u t r i e n t s SUPPLIES:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

T r a n s f e r by application o f m a n u r e a n d / o r w a s t e . T r a n s f e r by droppings on grazed areas . . . . . . . I n p u t b y application o f m a n u r e . . . . . . . . . . . . I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . I n p u t by N-fixation . . . . . . . . . . . . . . . . . . . . . I n p u t by application o f litter, sludge and w a s t e . I n p u t by irrigation and flooding . . . . . . . . . . . I n p u t b y d r y and w e t d e p o s i t i o n . . . . . . . . . . . T r a n s f e r b y w e a t h e r i n g o f soil m i n e r a l f r a c t i o n . . T r a n s f e r by m i n e r a l i z a t i o n o f soil organic fraction T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g on field . T r a n s f e r b y seed for s o w i n g . . . . . . . . . . . . . . TOTAL

R E M O V A L S : 19. 20. 21. 22. 23. 24. 25. 30t. 30r.

O u t p u t by d e n i t r i f i c a t i o n . . . . . . . . . . . . . . . . O u t p u t by volatilization o f a m m o n i a . . . . . . . . O u t p u t by leaching . . . . . . . . . . . . . . . . . . . . O u t p u t by r u n - o f f o f available n u t r i e n t s . . . . . . O u t p u t b y dust . . . . . . . . . . . . . . . . . . . . . . T r a n s f e r b y fixation in soil m i n e r a l fraction . . . . T r a n s f e r b y i m m o b i l i z a t i o n in soil organic fraction T r a n s f e r b y n e t u p t a k e b y the p l a n t . . . . . . . . . T r a n s f e r b y n e t u p t a k e b y the p l a n t . . . . . . . . . TOTAL

-90 5

-- -90 5 --

5

5

6 60 -166

3 32

--

135

-------166 -166

135

0

0

SUPPLIES-REMOVALS

135

Changes in a m o u n t o f soil organic m a t t e r SUPPLIES:

8b. 9b. 10b. 13b. 25. 26b.

R E M O V A L S : 17. 28.

Transfer by application and/or waste . . . . . . . . T r a n s f e r b y d r o p p i n g s on grazed areas . . . . . . . Input by application of m a n u r e . . . . . . . . . . . . I n p u t b y a p p l i c a t i o n o f litter, sludge a n d w a s t e T r a n s f e r b y i m m o b i l i z a t i o n in soil organic fraction T r a n s f e r b y p l a n t p r o d u c t s r e m a i n i n g o n field . . TOTAL .

T r a n s f e r b y m i n e r a l i z a t i o n o f soil organic fraction O u t p u t by organic m a t t e r , r e m o v e d b y r u n - o f f . . TOTAL SUPPLIES-REMOVALS

----

-

-40 40

22 22

6

3

-6

3

+34

+19

Changes in a m o u n t o f soil minerals SUPPLY: REMOVAL:

24. 16.

T r a n s f e r b y fixation in soil m i n e r a l fraction . . . . T r a n s f e r b y w e a t h e r i n g o f soil fraction . . . . . . . SUPPLY-REMOVAL

--

166 The net effect of recycling through animals on the equilibrium levels of nitrogen flows and pools is a reduction in the "effective" utilization (harvesting) fraction of nitrogen compared with the utilization fraction of biomass. Thus, for a given environment and a given biomass utilization level, grazing-recycling allows higher equilibrium yields than direct harvesting (Table 51).

6.7.3.8. Intensive grain farming Classification: Intensive grain system. Reference: Noy-Meir and Harpaz-5; Intensive Israelian grain farm, semi-arid area, grain harvested, straw returned, Table 54. Intensive grain system. Reference: Noy-Meir and Harpaz-6; Intensive Israelian grain farm, semi-arid area, grain and straw harvested, Table 54. The effects of adding nitrogen fertilizer will be considered with reference to the extensive system as described in section 6.7.3.4. If 90 kg N ha- 1 are added annually (roughly the a m o u n t used in intensive wheat farms in the Negev), the mineral nitrogen input to the system, i is increased from 10 to 100 kg ha- 1. If this has been done for long enough, so that the stable organic matter has attained equilibrium with this input level, all nitrogen levels and flows will simply have increased by a factor of 10 (equations 8--16). A more c o m m o n situation is that fertilizer application is only beginning, and the organic N is still near the level which was the equilibrium for the previous (unfertilized) system. The initial effect of fertilization on flows and yields and on the accumulation of organic N, at different utilization levels, is demonstrated in Table 53. The much higher flows and yields calculated for the fertilized systems are based on the assumption that production is limited by nitrogen, n o t by water. Thus they are expected to be realized only in years in which rainfall is sufficiently abundant for this to be true. The threshold rainfall for nitrogen limitation will of course be higher in the fertilized system; with i = 100 it can be estimated to be roughly a b o u t 400 mm (250 mm transpiration + 150 mm evaporation). In years with abundant rainfall and favourable distribution, grain yields of 3500--4500 kg ha- ~ are indeed obtained in wheat fields in the Northern Negev, with this fertilization level.

6.7.4. Conclusions Plant production in semi-arid agro-ecosystems is determined by the natural supply of nitrogen at least as much and as often as by the water supply. The depletion of the soil nitrogen by high utilization and low inputs over hundreds of years is probably a major reason for the generally low yields of crops and pastures obtained (even in the best years) in the traditional agro-

167

ecosystems in the semi-arid belt of the Middle East and North Africa. In the balances it has been assumed that by 1950--1960 the decline had approached very closely to a new (low) equilibrium, and the annual mineralization may be neglected. The regular addition of nitrogenous fertilizer to these agro-ecosystems can cause an immediate j u m p in yields (by a factor of 2--8), and a slower increase in the stable soil nitrogen reserve. In extreme drought years the response may be slight, but in all other years it is substantial and (at present price ratios) economically justifiable (up to 100 kg N ha- 1 y - , at least). Since leaching is negligible (and other losses small), most of the nitrogen left unused in a dry year is used in subsequent years, and the overall utilization efficiency of the fertilizer added is high. For the same reason, the danger of groundwater pollution by N fertilizers is n o t expected to be serious in non-irrigated semi-arid ecosystems. 6.8. AGRO-ECOSYSTEMS IN JAPAN (M. Yatazawa)

6.8.1. Introduction

The structure of agro-ecosystems in Japan is very complex, and it is very hard to delineate certain units of agro-ecosystems of reasonable size which could be separated from others and within which the flow of material may be measured. Also, even if there were separable agro-ecosystem units of suitable size, there are no data on material flow which may be used. Therefore the cycling of nutrient elements in agro-ecosystems is first to be estimated macroscopically by preparing a balance sheet of such elements as average values for the entire country, with reference to some major cropping systems. Arable land use in Japan

In 1972, the total area of arable land in Japan was 5683 X 103 ha, including 3312 X 103 ha p a d d y fields, 1356 X 103 ha uplands, 627 × 103 ha tree plantations, and 389 X 103 ha grasslands. The degree of utilization is 93.3% for p a d d y fields and 114.7% for uplands (MAF, Statistics and Information Bureau, 1974). The former represents fallow which has appeared in recent years, and the latter indicates that a few uplands are used for more than one crop a year on average. Grasslands, 77% of which are located in the Hokkaido District, include some waste lands. The total cropped area in 1972 is shown in Table 55. The sum of the area for upland rice, wheat and barley, potatoes, pulses, and vegetables in Table 55 exceeds the area of upland in the whole country. This is because the former includes areas carrying two crops a year as well as areas of winter crops on drained p a d d y fields. The area for forage crops in Table 55 also exceeds the area of grasslands. This is because forage crops are grown on uplands and on drained p a d d y fields.

168

TABLE 55 Total area of cropped land

r

Type of crop

Surface area (1000 ha)

Paddy rice Upland rice Barley + wheat Potatoes Vegetables Fruit trees Industrial crops Forage crops

2581 59 260 237 676 428 406 816

Thus, Japanese agriculture could be classified roughly into the following three groups. (a) Paddy fields: mainly occupied by a single crop of rice. Other crops on paddy fields and winter crops (wheat and barley, Japanese milk vetch, etc.) on drained paddy fields are included. (b) Uplands: upland crops (upland rice, wheat and barley, potatoes, pulses, etc.), vegetables, and forage crops are grown. (c) Tree plantations: this group includes orchards, mulberry farms and tea gardens. Components o f input and output o f nutrient elements in arable land Input of nutrient elements into arable land is chiefly through fertilizers, irrigation water, and precipitation. Nitrogen also enters the system through biological nitrogen fixation from the atmosphere. On the other hand, output of nutrient elements from arable land is through harvested products, leaching, and run-off. In addition, nitrogen is lost through denitrification and volatilization. Input of fertilizers and output by harvested products differ from crop to crop, and the amounts are described in later sections in which the balance

800

•

g

0/*-0%

E

//

_O~-o~'

~ 6oo

O

500

-

a

. . . .

1960

I

1965

,

,

,

,

I

1970

,

,

I

1973

Fig. 18. T h e national trend in fertilizerconsumption in 10 6 kg per year. • P2Os; x-----x K~O.

• N; n

169 of nutrient elements in each cropping system is considered. The national trend in fertilizer consumption is shown in Fig. 18. Other components of input and o u t p u t of nutrient elements are shown in the following sections.

Precipitation. Precipitation in Japan contains on average, 0.2--1 ppm combined N, 0.01--0.04 ppm P, 0.1--0.3 ppm K (Sugawara, 1963; Civil Eng. Soc. Japan, 1972, 1973). The total a m o u n t of annual precipitation in the whole c o u n t r y is estimated to be 6.3 X 1011 m 3 , corresponding to 1.7 X 104 ton per ha annually. From this value the a m o u n t of input into arable land per ha can be obtained (Ukita et al., 1972; Civil Eng. Soc. Japan, 1972; Takeuch and Hasegawa, 1974). On average, the following values may reasonably be adopted; N: 5 kg, P: 0.2 kg, K: 4 kg.

Irrigation water. The quality of water in irrigation streams has fluctuated greatly in recent years. Therefore average values for water quality were calculated from the data on non-polluted water quality before 1960 and on polluted water quality after 1960 (AAF, 1969). The Ministry of Agriculture and Forestry reported in 1969 that about 6% of paddy fields were being damaged to a greater or lesser extent by polluted water, a large part of which was eutrophic water (MAF, 1970). Therefore, the average value of irrigation water quality in the whole country was obtained by summing the t w o components of polluted and non-polluted water quality, multiplied by each irrigation area. The average a m o u n t of water used to irrigate paddy fields is estimated to be 15 000 t ha -~ y-~. Irrigation for upland is estimated to be 6000 t ha -~ y-~ (Kano, 1962) and the water quality is assumed in this report to be an average value for nonpolluted irrigation water. These data are shown in Table 56. TABLE 56 Mineral nutrient content and annual influx of irrigation water

Non=polluted water (ppm) Polluted water (ppm) Influx into paddy (kg ha-' )* Influx into upland (kg ha-' )**

N

P

K

0.32 12.54 16.5

0.01 0.2 0.4

1.64 4.11 27

1.8

0.0

10

*Including 6% of polluted water. Annual water influx: 15 000 t ha -1. **Non-polluted water only. Annual water influx: 6000 t ha-'.

N2 fixation. Atmospheric nitrogen is fixed in arable land mostly by bluegreen algae, legume-rhizobium symbiosis and free living micro-organisms. N2 fixation by blue-green algae was reported to be 0.4--0.5 mg kg -1 soil in the laboratory (Okuda and Yamaguch, 1956). In field experiments, using l SN,

170

Tolypothrix tenuis f i x e d o n average 2 2 . 5 kg N h a -1, o f w h i c h 4.8 kg h a -1 was a b s o r b e d b y rice p l a n t s (Nishigaki e t al., 1951). T h e increase o f y i e l d (rough rice) was 11.2% o n average in field e x p e r i m e n t s a t nine A g r i c u l t u r a l Experim e n t S t a t i o n s in 1 9 5 2 - - 1 9 5 6 ( W a t a n a b e , 1965). O n t h e o t h e r h a n d , l o n g - t e r m e x p e r i m e n t s indicate t h a t t h e a m o u n t o f N2 f i x a t i o n in p a d d y fields w o u l d be 2 0 - - 5 0 kg N h a -1 ( W a t a n a b e , 1971), even t h o u g h t h e e s t i m a t i o n was m a d e f r o m i n d i r e c t evidence. N2 f i x a t i o n b y l e g u m e - r h i z o b i u m s y m b i o s i s in u p l a n d s is e s t i m a t e d t o be 1 0 0 kg N h a -~. N2 f i x e d b y free-living m i c r o - o r g a n i s m s is e s t i m a t e d t o be 20 kg N h a - 1 in u p l a n d s and 5 kg N h a - 1 in forests, e v e n t h o u g h we h a v e n o direct determinations.

Run-off. Earlier J a p a n e s e r e p o r t s ( W a t a n a b e , 1 9 7 2 ; H i r o s h i m a Agric. E x p t . Stat., 1 9 7 2 ) reveal t h a t loss o f n u t r i e n t s f r o m u p l a n d b y r u n - o f f , o n average, TABLE 57 Leaching ratios Leaching from fertilizer applied (leaching from nonfertilized plot was subtracted) (kg ha -1)

Leaching from fertilized plot (leaching from nonfertilized plot was not subtracted) (kg ha -1 )

N

N

P

K

P

Soil type

Reference

K #

Paddy 1.2 18.0

---

9.1 3.7

0.5 --

---

7.4 31.0

---

---

reductive oxidative

--

28.5

--

--

oxidative

--

31.7

--

--

semi-wet, even Irizawa and Yamane, in off-season } 1963

--

3.4

28.7

--

0.7

31.6

weakly aged } (akiochi) I Tokai-Kinki Natl. strongly aged Agric. Expt. Stat., (akiochi)

} Okuda, 1960 Civil Eng. Soc. Japan, 1972

1 9 6 9

Upland

33.1

oManaan

Cj

x° o.

' F ' M ' A MI j ' I j ' A S' , O ~ N D Month

,, _ ur'Dana Q

Sp~ngfield • / \e /

"

/,~" ° ®"~ °'°-~ ~ /~Youngstown "\~'o ©

2.~ C J , F~M~A~M'J JJ ~A S~O , J N D , Month

Fig. 22. Monthly precipitation for three Great Plains locations (Mandan, North Dakota; Grand Island, Nebraska; and Lubbock, Texas). Fig. 23. Monthly precipitation for three Northeast locations (Urbana, Illinois; Youngstown, Ohio; and Springfield, Massachusetts).

186

I Little R o c k a..eR . • 12.5~-o ~\?x~ e / \ aJelgn 5 10.01- ',,~ I/_ r ~ . _

~,

I/-

X £';

RoJofo,,

cm/mo 7 ,=L" ~''.asnv,, ~ ~'',e ~ - " " ~ \, /~~/ /. . / 5C 2.E Cj

I

I

~

I

I

E

k

I

I

h

FMAMJ J A S O ND Month Fig. 24. Monthly precipitation for three Southeast locations (Little Rock, Arkansas; Nashville, Tennessee; and Raleigh, North Carolina). The Southeast. The Southeast is very much like the Northeast in precipitation except that yearly rainfall is higher (100--125 cm) and that more of the rain falls in the winter (Fig. 24). There is a distinct dry period during September-November in all of the Southeast and there is a tendency for more rain to fall in the winter in the areas west of the Appalachian mountains. In this midsouth region, the warm, moist Gulf air meets Arctic cold fronts in the winter, much like they are met on the Great Plains during the summer. East of the mountains (Raleigh, North Carolina), less effect is seen. Another sharp difference between the Atlantic Coast and the Continental portion of the Southeast, is the sharp rise in shower activity away from the coast during March-May. This is analogous to the increase in rainfall in the Great Plains, and is most often due to huge thundershowers often accompanied by tornadoes. Because of the high winter rainfall, there is ample water to move soluble nutrients o u t of soils in most of the Southeast. Water available for leaching varies from a high of 50 cm to a low of 2 5 cm, about the range found in the Northeast. However, the difference is that more excess water is available in the Mississippi Valley and less along the Atlantic Coast, just the reverse of the situation in the Northeast. Florida. Florida stands b y itself climatically. It has very high rainfall which occurs almost exclusively in the summer (Fig. 25). Thus, the pattern of rainfall is much like that in the Great Plains, b u t the amounts are even greater than those in the Southeast as a whole. The low winter rainfall in Florida results from the infrequent penetration of Arctic air b e y o n d northern Florida in the winter. The high summer rainfall is a result of the evaporation of water from the Gulf of Mexico and the Atlantic Ocean and the rising hot air from the land surface of Florida. This effect triggers thousands of local thundershowers on summer days throughout Florida. Although the average rainfall is very

187

25 Rainfall,

/1.4ia mi -

20

o / /:#'~"X

#:~ \

lc/o/ ,,ohossoe\ ? 5 *-*/e' o

°-°~ e

J FMAMJ J SOND Month

Fig. 25. Monthly precipitation for two Florida locations (Tallahassee and Miami).

high, the year-to-year variation is also great because of the small average size of each thundershower. Since most rain in Florida occurs in the summer, the net water available for nutrient leaching is somewhat smaller than in the rest of the Southeast. However, because of the year-to-year variation in rainfall, it is difficult to predict exactly h o w much leaching will occur. Another factor which increases leaching in Florida is the generally sandy soils with low water-holding capacity.

6.10.1.2. Temperature Temperature affects nutrient losses in several ways: b y affecting the rate of oxidation of soil organic matter, b y determining the duration of plant growth and b y determining which plants will be grown. Mean annual temperatures for the 48 conterminous United States are shown in Fig. 26. This figure shows that there is a minimum of 4.5°C for the northernmost states and a maximum of over 21°C along the southern border. The Van 't H o f f rule indicates that for each 10°C rise in temperature, the rate of chemical reaction will double or triple. Jenny (1930) has shown fairly good correspondence with this rule for organic matter decomposition in soils of temperate regions. This implies that, if there is sufficient substrate present, the decomposition of organic matter and concurrent mineralization of organic nitrogen and phosphorus will proceed faster as one moves towards the south. There is one problem in this approach, however, -- the generally lower a m o u n t of organic nitrogen and phosphorus present in southern soils. In cases such as organic soils there is no question that Van 't Hoff's rule applies. Comparison of work done in Ontario, Canada by Nicholls and MacCrimmon (1974) and that done in Florida b y Hortenstine and Forbes (1972) shows that much more nitrate and orthophosphate was formed under the Florida conditions.

188

Fig. 26. Mean annual temperatures in the United States.

The length of the growing season varies from 100 days along the northern border to 365 days at the tip of Florida. Over the largest part of the United States, the growing season is 140 days or longer. In these areas, the growth of corn and other summer crops is practised. Typically, the soil is deficient in water and nutrients during the months of July, August and September, b u t during the months of May, June and October mineralization of nitrogen occurs, making losses by leaching possible if rains occur. During the winter, over the humid part of the United States, nitrate oxidized during the warm season is subject to leaching, b u t nitrification of more nitrogen occurs only infrequently. Further south, below the 15.5°C mean annual temperature line, mineralization of nitrogen can occur most of the year, and in the humid part of the country severe losses can be expected. In the extreme northern part of the country, softs freeze solid so that leaching does n o t occur during the winter. However, as soon as the ice melts in the spring, any nitrate in solution is subject to movement. Crop selection is also governed by temperature, with the effect of changing both uptake of nutrients and fertilization rates. In general, corn receives the highest rates of fertilizer, followed b y c o t t o n and wheat. Corn is grown mostly between the 4.5°C line and the 15.5°C line, b u t wheat is grown at all latitudes. The distribution of these crops is treated at length in other sections.

189

6.10.2. Soil characteristics of the various climatic regions This section will be devoted to explaining the soil differences within and between climatic regions of the United States. Major emphasis will be placed on soil properties which most strongly influence nutrient loss and/or accretion. Of necessity, this section is over-simplified so that general conclusions can be drawn.

6.10.2.1. Pacific region Soils used in agriculture in the Pacific region can be divided into three general classes: irrigated, humid region soils and Aridisols. Much more is known a b o u t the irrigated soils than a b o u t the other t w o groups because they are used intensively for high-value crops.

Irrigated soils. The huge central valley of California, parts of southern California and areas in Oregon and Washington contain soils which are used intensively for crops. Most of these soils are formed in deep alluvium (mostly old) which comes from both crystalline and sedimentary rocks in the mountains. These soils are deep, have gentle relief, moderate to high nutrient content and nearly always have groundwater beneath them. These soil areas have received high rates of nitrogen, especially over the past 30 years, and, in addition, the native nitrate was high in some areas (Dyer, 1965). Recent work b y Californian workers (Pratt and Adriano, 1973) has shown large concentrations of nitrate deep in the soil, which is moving towards the groundwater. Since water for dilution is not obtainable, there is no way to lower nitrate concentrations of groundwater for many years, even if land use and fertilizer rates are changed. In addition to problems with nitrate, there are many soils throughout the region which are high in sodium (Storie and Weir, 1953). The largest concentration of these soils is found in the Imperial Valley on the California--Sonora, Mexico border. In this valley, drainage is poor, rainfall is a b o u t 5 cm per year and irrigation water quality is generally low. Chances for improving any of these factors are remote.

Humid region soils. Along the foothills of the Sierra Nevada range, in much of northern California and along the coasts of Oregon and Washington are found soils which receive rainfall amounts of from 60 to 225 cm per year. As mentioned in the section on climate, most of this occurs during the fall, winter and spring seasons, and there is a distinct dry period during the summer. Thus, these soils tend to lose nutrients during the rainy season when evapotranspiration is low. However, because these soils have moderate to high iron oxide contents, they tend to absorb anions (Chao et al., 1962) so that losses are lower than would be expected. In addition, because of the moderate winter temperatures throughout the region, considerable growth by plants takes place, which removes some of the potentially mobile nitrate.

190

Softs of this class are used for the very important grass and legume seed production of the northwestern U.S. Nothing has been reported about nutrient cycling under this use.

Arid soils. Soils of the deserts and near-deserts (Aridisols) in the Pacific region make up a large portion of the landscape but have almost no cultivation and very low livestock density. Since the rainfall averages only about 10 cm there is little chance for movement of nutrients to occur. Most softs are not well developed and organic nitrogen contents are very low. 6.10.2.2. Intermountain region Agricultural land in the intermountain region is of three kinds: irrigated (intensive), which makes up only a small fraction of the region (Table 65); dryland wheat, important in Washington, Oregon, Idaho and Montana; and rangeland. In addition, a large part of the area is dominated by high mountains which furnish the water for irrigation and are grazed by some cattle and sheep during the summer. The region is one of great contrast in both climate and soils, with the largest differences being caused by elevation. Irrigated soils. Most irrigated soils in the intermountain region occur in rather old alluvium from mixed crystalline and sedimentary rocks. T h e y TABLE 65 Hectares irrigated by states and percent of land area irrigated (U.S.D.A., 1973) State

Kansas Nebraska Florida Arkansas Louisiana Oklahoma Texas Montana Idaho Wyoming Colorado New Mexico Arizona Utah Nevada Washington Oregon California U.S.

Area (1000 ha) 1157 616 553 409 284 212 2790 746 1118 617 1172 333 477 415 305 496 615 2932 15847

% of area irrigated

5.4 3.1 3.6 3.0 2.3 1.2 4.0 2.0 5.2 2.4 4.3 1.0 1.6 1.9 1.1 2.8 2.4 7.1

191

receive less rainfall on average and it is better distributed through the year, so that they are less weathered than the irrigated soils in California. In most cases they are calcareous, whereas many of the California soils are not. As in the Pacific region, the softs are deep and underlain b y groundwater, but, for the most part, the irrigated valleys are smaller and less intensively used than in the Pacific region. Typical crops are small grains and potatoes in the north and c o t t o n and citrus in the south. Rainfall averages 35 cm yearly in the north to a b o u t 15 cm in the south, b u t irrigation water adds from 60 to 120 cm more depending u p o n crops and growing season. Total irrigated area in each of the states is shown in Table 65. Throughout the region, salts are a problem (Thorne and Peterson, 1954) and it is likely that an increase in nitrate will occur as in the Pacific region, since fertilization has increased very markedly in the recent past.

Dryland wheat. The foothills with gentle relief and slightly higher precipitation are used for wheat, especially in the northern half of the region. Preparation is minimal, fertilization is low, and yields generally are marginal, fluctuating wildly from year to year. Cultivation appears to have a negligible effect on nutrient losses other than by increasing erosion in some years.

Rangeland. Use of rangeland is at a very low animal density. At stocking rates of one cow to 20 ha it is doubtful that the effect can be measured. Rainfall is in the neighborhood of 25 cm per year and little nutrient loss from the soft is expected.

6.10.2.3. Great Plains region The Great Plains (Fig.19) includes many diverse climatic and agricultural systems. However, one problem that is c o m m o n to the whole region is one of inadequate and erratic precipitation. Soils formed in this region generally are productive and fertile, b u t lack of water prevents full utilization of their productivity in much of the region. Soils of the order Mollisols predominate. These soils were formed from recent material (glacial till and aeolian deposits) under grassland vegetation. Precipitation ranges from 50 to 75 cm per year on average, b u t distribution and dependability from year to year are worse than in any other region o f the United States. For example, Victoria, Texas received its annual rainfall average in two days in 1967 (Thomas, 1967). This erratic rainfall has t w o consequences which favor nitrogen loss from soils under cultivation. In a dry year, nitrogen is n o t used by the crop in high amounts. If this is followed b y a wet year, nitrogen is moved o u t of the soil. Data from southwestern Iowa (Burwell et al., 1976) show this conclusively. Irrigation is practised to a considerable extent in Nebraska, Kansas and Texas (Table 65). In all three areas, it can be expected that nitrate will be moved o u t of the soil towards the ground water even farther than b y natural rainfall alone. However, the average concentration will be lower.

192

6.10.2.4. The northeastern region The northeastern region must be divided into two general soil regions. From Ohio west, the corn belt softs are generally higher in organic matter and in nutrients than soils further east. They also are more likely to be in cultivation. Fertilizer nitrogen use is many times higher (Fig. 27) because of this. In the eastern part, agriculture is important only in the middle Atlantic States.

N Ap

>3O 20-30 10 - 2 0 5 -10 < 5

"

I

I

Fig. 27. Fertilizer nitrogen use in the United States.

Corn belt. Soils in the corn belt are mostly Mollisols with some Alfisols.Most of these soilshave developed in recent material under s w a m p y conditions which no longer exist because of an extensive system of both underground and surface drainage developed during the past 150 years. These soils are characterized by fairlyshallow water tables, dark surface horizons and level topography. Cultivation and rotation with legumes provided the nitrogen which produced the vast amounts of corn grown there until 15 years ago. Johnson et al. (1975) have shown that even with the largestuse of nitrogen in the United States, the amounts of nitrogen removed in crops exceed fertilizationrates in most years. Nitrogen losses have been high since the area was settled,and they are probably rising.Data in Table 66 show that rivers draining Illinois,Missouri and Iowa were far higher in nitrate in 1907 than were streams from the Southeast.

193 TABLE 66 Average NO3-N in rivers during 1907 (Dole, 1909) State

River

NO3-N (ppm)

Illinois Illinois Illinois Illinois Illinois Illinois Missouri Iowa Iowa

Big Vermillion Embarrass Fox Illinois Kaskaskia Little Vermillion Missouri Des Moines Iowa

2.71 1.71 1.10 1.76 1.56 2.71 0.65 0.75 0.63

Virginia Alabama North Carolina North Carolina Virginia Kentucky

James Alabama Cape Fear Neuse Dan Kentucky

0.07 0.16 0.04 0.07 0.25 0.56

6.10.2.5. Middle Atlantic States and New England Most soils in this area are Alfisols with some Spodosols (Podzols). These softs are medium to low in nutrients, including nitrogen, but in m a n y areas have been made highly fertile by long fertilization. Because of the low density of cultivated crops, water quality deterioration due to agriculture has n o t been a general problem. However, in some concentrated agricultural regions such as Connecticut, the imports of feed and fertilizer have greatly increased both phosphorus and nitrogen according to Frink (1969). Probably the greatest potential problem in the area is sedimentation of lakes by soil erosion and resultant eutrophication of the waters. Another problem is the pollution of water by the heavy population density and its resultant effects on agriculture. 6.10.2.6. The Southeast region Soils of the Southeast are dominated by the Ultisols, with important areas of Alfisols and Inceptisols. Many Ultisols have important properties which affect nutrient cycling. Ultisols. Ultisols of the southeastern U.S. were so low in nutrients before cultivation, that m a n y of them are accumulating nutrients (on a relative basis) faster than other softs in the United States. Although fertilizer use began earlier on them than on any other soils in the U.S., the heavy use of nitrogen has occurred only in the last 25 years. A high proportion of these softs in the Piedmont and Limestone Valley have subsurface horizons high in iron oxides which adsorb anions. Phosphate is adsorbed so tightly that essentially

194

no loss of added phosphorus occurs (Ensminger, 1954); sulfate is held with intermediate tenacity (Kamprath et al., 1956) and nitrate is held only loosely. However, nitrate is held strongly enough in many softs for it to lag behind the water front as winter leaching occurs (McMahon and Thomas, 1974). Under conditions where cultivated summer crops are grown (such as continuous corn) there is probably little effect of this nitrate adsorption on the nitrate content of water percolating from these softs. That is, the systems come to a steady state. However, when winter cover crops or small grain crops are grown, there tends to be a conservation of nitrate in these soils. Where rotation between grain and pasture crop is practised, the nitrate is simply not easily lost since it is taken up by the (usually) unfertilized forage crop. Examples of the long-lasting effect of nitrogen fertilization on red softs have been found by Boswell and Anderson (1964) and b y us (G.W. Thomas, unpublished work, University of Kentucky, 1970).

6.10.2.7. Soils with unusual properties Two types of soils which strongly affect waters in areas where they are found are presented below. These effects are of interest because of the unc o m m o n l y high amounts of nutrients lost, b u t also because they represent healthful, prosperous regions where people have not suffered the supposed ravages of high nutrients in waters.

Organic soils (Histosols). Soils which contain more than 20% organic matter occur mostly on the South Atlantic and Gulf Coasts, the Lake States and the Pacific Coast (Buol, 1973). In every area in which they occur, rather intensive use is made o f some of them for high value crops such as sugar cane, potatoes, vegetables, corn and soybeans. These softs were formed as a result of swampy conditions, and drainage is practised in all cultivated areas. As a result of the cultivation and drainage of organic soils, the organic matter may be rapidly oxidized. Although C : N ratios are wide (about 20), the total nitrogen mineralized from such soils can be very high (Hortenstine and Forbes, 1972), at least under Florida conditions. In North Carolina where such soils are extremely acid, losses of nutrients are n o t as severe (J.W. Gilliam, unpublished work, North Carolina State University, 1975). In addition, many organic soils do not hold phosphorus very strongly, and when fertilized tend to lose phosphorus (Okruszko et al., 1962). Oxidation of organic matter causes even more loss. Organic soils do not represent a large area of the United States, but, where they are found, they can profoundly affect the surface and ground waters. High phosphate soils. In Florida, Tennessee and Kentucky are found softs formed from high phosphate limestone. In these areas, both nitrogen and phosphorus losses are high because of the exceedingly fertile softs. All three areas are predominantly in grasslands, which, generally, would be expected to temper loss of nutrients. However, the phosphorus levels are so high through-

195 o u t the soil profile that b o t h grasses and legumes thrive. At their death (in winter), large amounts of nitrate are released to the soil solution. We (Thomas and Crutchfield, 1974) found that a stream draining a high phosphate area in Kentucky averaged 0.32 ppm of dissolved phosphorus and 5 ppm NO3-N over a two-year period. Both values were higher than for any other soil area in Kentucky. Very early work of McHargue and Peter (1921) showed the same trend before any fertilizer was used. Recent work (G. Lessman, unpublished work, University of Tennessee, 1975) in Tennessee showed a phosphorus content of 0.34 ppm in r u n o f f from a high phosphate soil watershed. These values for phosphorus are so high that man-made changes do n o t generally compare with them. 6.10.3. Agricultural systems

Types of farming in the United States are changing at a rate perhaps unmatched in the rest of the world. As an example, the production of soybeans in 1945 used a b o u t 4 000 000 hectares. In 1975 there were more than 21 000 000 hectares used for soybeans (U.S.D.A., 1975). Cattle production has shown a similar growth and geographical movement. Therefore, farming regions are somewhat arbitrary and transient, b u t offer a rough guide as to what is to be expected in a given area. The major types of farming in the United States follow. General information for this section was taken from Marschner (1959). 6.10.3.1. The corn belt The so-called corn belt of the Unites States includes all of the states of Iowa and Illinois and significant parts of Nebraska, Minnesota, Kansas, Missouri, Indiana and Ohio. In this region several factors combine to make the production of corn more economical than in any other part of the country. These factors are soil, rainfall and topography. The soils of the corn belt vary from Alfisols to Mollisols but, in general, are formed on y o u n g material and have moderate to high natural fertility. However, b y far the most important quality they possess is a high water supplying capacity (Shaw et al., 1972),' which usually is a combination of good soil water storage and a contributing water table. Franzmeier et al. (1973) for example have shown that t w o of the best softs for corn production in Indiana have water tables that contribute to the soil water supply. Rainfall in the region has been discussed in section 6.10.1, b u t it is worth mentioning again that in the western edge of the corn belt summer rainfall is nearly as high as in the eastern side of the corn belt, even though total rainfall is 25 cm lower. Finally, the land surface is sufficiently level for large-scale mechanized agriculture. More than a century ago, many of the original inventions which have mechanized agriculture were made in response to the o p p o r t u n i t y presented by this productive farming region.

196

~-:~ ~ ~

i'

f

Percentage of Land in C o r n > 30 °/o 20 - 30 °/o 10-20°/o 4-10°/o Fig. 28. Percentage o f land used for corn in the United States.

Hog Density < 5 ha/hog 5-10 ha/hog ~10 ha/hog Fig. 29. Density of hogs in the United States.

197

All Cattle 10 ha/animal r--J Fig. 3 0 . D e n s i t y o f

"

~ i

all cattle in the United States.

T h e c o r n b e l t is still t h e largest p r o d u c e r o f c o r n in t h e U.S., b u t it is also t h e largest p r o d u c e r o f s o y b e a n s . S o y b e a n s are g r o w n o n land o n c e u s e d f o r oats a n d h a y a n d t h e i r c u l t i v a t i o n was m a d e possible b y t h e d i s a p p e a r a n c e o f t h e horse. A t p r e s e n t , t h e c o r n b e l t is a c o m b i n a t i o n o f t w o m a j o r agricult u r a l s y s t e m s . T h e first, a n d t r a d i t i o n a l c o r n b e l t agriculture, is t h e raising o f TABLE 67 Nutrient inputs and removals in Iowa N Inputs

P (1000 rot)

K

Animal manure N-fixation

408 359

99 --

Rain Fertilizer

163

--

---

681

158

347

1611

257

663

Total

316

Removals M e a t , m i l k , eggs

106

6

25

Corn

391

56

136

Soybeans

391

13

32

Total

888

75

193

198

corn and hay and the feeding of cattle and hogs. To a large extent, this system still prevails in Iowa and around the fringes of the belt proper. Thus, Iowa leads in area devoted to corn (Fig. 28), leads in hogs (Fig. 29) and stands highest in total cattle density (Fig. 30). In addition, it ranks second in fertilizer nitrogen use. From this it is apparent that nitrogen additions to the softs of Iowa are by far the highest in the United States. Table 67 shows the inputs and removals of nutrients in Iowa. A large portion of the inputs comes from animal manures. In contrast, the corn-soybean cash crop rotation used especially in Illinois is likely to lose nutrients from the farm since most of the grain is exported rather than fed (Johnson et al., 1975). As a general rule, the second type of operation is becoming more c o m m o n as cattle are raised and fattened away from the corn belt and as hogs become relatively less important. The cash grain system has become more popular as prices of grain have risen relative to meat prices. 6.10.3.2. The Great Plains The Great Plains are similar to the corn belt topographically, and softs are just as fertile with the exception of nitrogen. What is lacking in the Great Plains is rainfall. However, since the limited rainfall is concentrated in the spring (Fig. 22) the production of wheat has been successful. Wheat is grown from Canada to Texas, mostly for export, not only from the area, b u t from the United States. Fertilizer use is moderate, b u t so are yields so that only the vast area accounts for the large wheat production. Mechanization is on a much larger scale even than in the corn belt. Other crops which are important are corn, grain sorghum, cotton, potatoes, flax, alfalfa and sugar beets. Most corn and sugar beets and much of the cotton are grown under irrigation. A recent introduction to the area is beef cattle feeding on a large scale, made possible by the lack of winter rainfall. The largest units in the world are located in eastern Colorado, western Nebraska, Kansas and the panhandle of Texas. From calf and feed grain exporting regions, these areas have changed to calf and feed grain importing regions in the past 15 years. 6.10.3.3. The Southeast The Southeast contains the old c o t t o n and tobacco belts and includes much of the general farming region of Appalachia. Like most of the rest of the United States east of the 100th meridian, however, soybeans are the most important crop in the area, followed closely b y corn. In contrast to the corn belt, much more of the land is in forest, and to an increasing extent, improved pasture. Cotton now is concentrated in the Mississippi delta (Tennessee, Mississippi, Missouri, Arkansas and Lousiana), the high plains of Texas and in irrigated valleys of Arizona and California. Tobacco is concentrated in south-central Virginia, eastern North and South Carolina, east Tennessee and central Kentucky. Peanuts are grown most intensively in eastern Virginia and North

199

Beef Cow < 10 20 >

10 20 40 40

ha/cow ha/cow ha/cow ha/cow

[[]~ i---]

Fig. 31. Beef cow density in the United States.

Carolina, southwest Georgia and southeast Alabama and on sandy softs in central Texas and Oklahoma. The largest change in the Southeast is the beef cattle "cow-calf" enterprise which has so markedly changed the looks of the landscape. Beef cow density in the Southeast is far greater than in the west and is as great as in the Great Plains (Fig. 31). Furthermore, the trend is continuing. Most of this enterprise is a result of improved pasture and hay and, unlike the corn belt, grain plays a rather small part. In some parts of the region, cattle far o u t n u m b e r people. In one central Kentucky c o u n t y (Lincoln} there are five cattle for every person (Koepper, 1975}. Inputs and removals of nutrients in Kentucky are shown in Table 68. The total values are much lower than for Iowa, but the proportional removal is lower, especially with P and K. Kentucky would be typical of the Southwest in this respect. In addition to cattle, chickens (for frying) are concentrated in the Southeast with largest numbers in Georgia, Alabama, Florida and Arkansas. Egg production, on t h e other hand, is concentrated in the Northeast and California. Hogs are an important enterprise in the Southeast, with Kentucky and Georgia the most important states (Fig. 29). This reflects the importance of corn in the two states. In general, the Southeast produces too little corn for its livestock enterprises so that it is an importing region. Soybeans are produced in excess, however, and much of the crop is exported to Europe.

200

T A B L E 68 N u t r i e n t i n p u t s and removals in K e n t u c k y N Inputs

P (10 ~ k g )

K

Animal m a n u r e N-fixation Rain Fertilizer

134 115 117 110

32 --42

120 --95

Total

476

74

215

55 31 52 9 9

3 4 2 1 1

15 11 4 9 2

156

11

41

Removals

Meat, milk Corn Soybeans Tobacco Wheat Total

A locally important enterprise is vegetables and fruits. Florida is by far the most important state in this regard, but Virginia, North and South Carolina, Georgia and Texas also are important. Crops which are important are citrus, peaches, apples, vegetables and potatoes. Forests comprise about half the area and, since most are privately owned, provide considerable farm income. This is most important in the coastal plain from Virginia to Texas, where pine for building houses and making pulpwood is a large industry. Hardwood forests in the mountains supply t h e furniture industry. 6.10.3.4. The Northeast The Northeast comprises the dairy belt of the United States, with Wisconsin, New York, Pennsylvania, Maryland and Vermont being most important (Fig. 32). These areas are mostly in grass, alfalfa and corn where farmed, but forests comprise more of the land than all other uses put together. In addition to dairying and forage, there are many smaller areas of tree fruits, some tobacco and speciality crops such as cranberries in Massachusetts and dry beans in Michigan. In contrast to the other regions, the Northeast has lost cropland and not replaced it with pasture. Some states such as New Hampshire and Maine have a very small area cleared and are almost completely in forests. Other areas, such as northern Michigan and Minnesota have been cut over for timber and now are essentially used for hunting and fishing. The westernmost states in the dairy belt differ from the eastern states both in productivity and population. Wisconsin and Minnesota have large agricul-

201

Dairy C o w Density 5 0 ha/cow i---1 Fig. 32. Dairy cow density in the United States. rural enterprises and are n o t being inundated b y cities. However, in states such as New Jersey, the population density is as great as in western Europe and taxes and high land prices have forced much land o u t of farming and into speculative hands. The Delmarva peninsula is an interesting small area within the Northeast. It has been farmed continuously since the 1600's and is one of the finest farm areas in the United States. It is a cash grain (corn and soybeans) area, much like parts of the corn belt, and offers a great contrast with neighboring areas. However, even in that region, dairy is of great importance. 6.10.3.5. The Intermountain West Agriculture in the Intermountain West is dependent upon water collected in the mountains both for irrigation of crops and watering of livestock. Farming tends to be of a general crop-livestock nature except in the state of Arizona. There, the climate permits intensive cotton, citrus and vegetable growing. The area irrigated is n o t large, b u t the average family farm is more prosperous than in any other state. In most of the rest of the region large-scale livestock raising or fairly large irrigated farms with cash crops are the only economic farming enterprises. Small irrigated farms are limited to small grains by the short growing season, together with small areas devoted to potatoes, vegetables and sugar beets. In general, the small family farm does n o t support families without extra income. Because the area is so vast, many cattle and sheep are raised, b u t the density is extremely low (in Nevada, for example, there is only one beef cow per 100 ha). Therefore, the effects of animals on

202 nutrient cycling are almost unmeasureable except in irrigated areas, which make up only 2--3% of the land area.

6.10.3.6. Pacific region The Pacific Coast is the most diverse farming area in the United States since it produces all the products that are found in the rest of the nation and several others in addition. The heart of this region is the central valley of California which produces all the raisins and almonds, most of the lemons, prunes, apricots, canned peaches and wine and 10% of the cotton produced in the United States. In addition, there are important areas of rice, citrus, grain and vegetables. The determining reasons for this diversity are climate and people. Of these, climate is most important. It has been noted that the Pacific Coast has a Mediterranean climate, and thus many Mediterranean plants have been introduced. The diversity is also partly due to the kinds of people who settled the region. Japanese vegetable and flower growers, Italian grape growers and Texas cotton growers are examples of the groups of agriculturalists who have moved their technologies to California. In the Northwest, a similar transference has occurred in fruit and potato growing, in the grass seed business and in forestry. Perhaps the real reason for the more organized farming in the region is the fact that it has developed later than the other regions and many of their mistakes were avoided. The results of these activities are both prosperity and problems. The problems arise from the labor needs during harvest (imported from Mexico) and from local pollution problems far worse than those found in the rest of the nation. Examples are air pollution from burning grass fields, water pollution from nitrate and the building of piles of manure within city limits.

1C~United States

8

N/° 0

mtMili°nSofof 6 Nutrient 4 per Year

1950

o~P~O~__~1 f,.~/® i ~ ® . . K20 I

l

1960

I

i

..-I

1970

Year Fig.33. Consumption of fertilizer nutrients in the United States since 1950.

203

6.10.4. Fertilizer use Introduction Use of fertilizer nutrients in the United States has increased rapidly during the past 15 years (Fig.33), but it appears t h a t in most parts of the U.S., the rate applied per unit area of cropland has stabilized at levels which reflect the climatic and soil limitations to crop yield. It appears that unless a drastic change in the relationship between crop prices and fertilizer prices occurs, there will be very small changes in the amounts of nutrients applied per unit land area. Changes in the near future probably will be associated with increases or decreases in cropland used. 6.10.4.1. Rates o f fertilizer nutrients used on specific crops Corn. Corn (Zea mays L.) is grown on approximately 25 000 000 hectares in the United States (U.S.D.A., 1975). Every state except Alaska grows a significant a m o u n t of this crop. Two states, Illinois and Iowa, grow more than a third of the corn crop (9 000 000 ha) and use 13% of the nitrogen fertilizer in the U.S. Corn as a crop uses a third of the nation's total nitrogen. The average rate of nitrogen used on corn is 115 kg ha -~ (Fig. 34) and the use

United States 12E ~ °"'o/

/1,o~°

o N ~

°\o-

100 Nutrient Rate on ~ i1~11::$;~ Corn, kg/ha 501

K20 P205

2~ L

C1967

I

I

i

1970 Year

I

i

I

1974

Fig. 34. Average rates o f fertilizer nutrients used o n corn in the U n i t e d

States.

varies only by about + 15 kg ha -1 from state to state. The phosphorus rate is about 30 kg P ha -1 and has remained at near t h a t level for the past seven years. The potassium rate on corn is 67 kg K ha -1. The percentages of the U.S. total phosphorus and potassium used on corn are 36% and 43%, respectively. From the above data, it can be seen t h a t corn is the biggest single user of fertilizer of any crop grown in the United States. This is due both to its large hectarage and to the relatively high rate of fertilization used.

204

Wheat. Wheat (Triticum sativum L.) is also an extensively grown crop in the United States. Most states have a considerable area devoted to wheat, and the total hectares in wheat production are about the same as in corn (25 000 000). Two states, Kansas and North Dakota, grow a b o u t a third of the wheat grown in the United States. As contrasted to corn, most wheat is grown in a generally drier climate and because of that and lodging problems, fertilizer use is considerably lower than with corn. Average nitrogen, phosphorus and potassium rates on wheat are given in Fig. 35. The nitrogen rate is 53 kg h a - ' , a b o u t half that on corn, and phosphorus and potassium rates are also a b o u t half as high. Because of the large area devoted to wheat, however, the total use of fertilizer nutrients is high. The percentages of the total nitrogen, phosphorus and potassium used on wheat are 15%, 22% and 21%, respectively. United States 60 Nutrient Rdte on 40

Wheot,

~.Lo--~--o~o /

N o/°---'° P~Os

~-"li=~i'--~8_---e~o---=l~==~K20

kg/h8

20 t

1967'

I

19'70

I

I

1974

Yeor

Fig. 35. Average rates of fertilizer nutrients used on wheat in the United States.

Soybeans. Soybeans (Glycine max B.) are the third most important crop in terms of cropland, and usually second or third in importance economically. Soybeans are grown mostly in the midwestern and southern corn states, but hectarage is also heavy throughout the Mississippi delta. Total hectares cropped to soybeans are 20 000 000. As in the case o f corn, a b o u t a third of the crop is grown in the t w o states of Illinois and Iowa. However, Missouri and Arkansas, neither of which are important corn states, rank third and fourth in production of soybeans. Because soybeans are legumes, they show little response to fertilizer nitrogen and very little is used. Rather high rates of phosphorus and potassium are used, however. In the East North Central States, for example, the average use of N, P and K is 12, 20 and 55 kg h a - ' , respectively. In the United States as a whole, rates are similar, with N being 15 and P and K 20 and 51 kg ha -1, respectively. The percent of total fertilizer used on soybeans is 3.5% of the N, 19% of the P and 26% of the K. The sum of fertilizer used on the three main grain crops of corn, wheat and soybeans is 52.5% of the nitrogen, 77% of the P and 90% of the K. These three crops make up 70 000 000 hectares of cropland in the United States. This is approximately 54% of the harvested cropland in the country.

205

Grain sorghum. Grain sorghum (Sorghum vulgare L.) is grown widely as a corn substitute where the annual rainfall is less than 75 cm. Most of it is grown in the states of Texas, Oklahoma, Kansas and Nebraska. The total area devoted to sorghum for grain is more than 6 000 000 hectares. Fertilizer use on grain sorghum has n o t been tabulated, b u t an estimate would be 70 kg N, 21 kg P and 17 kg K h a - ' . Most soils on which grain sorghum is grown suffer from some drought every year so that yield expectations are rather lower than for corn. In addition, most of the soils are well supplied with potassium, and little yield response from that nutrient can be expected. Cotton. Cotton (Gossypium spp. L.) is grown on about 5 000 000 hectares, widely scattered from North Carolina in the east to California in the west. Texas, Mississippi, Arkansas and California are the largest producing states. Because of the diversity of climates (both imposed and natural) under which c o t t o n is grown, fertilizer use differs radically. For example, in parts of Oklahoma, no fertilizer is used, whereas under irrigation in Arizona, rates as high as 140 kg ha-' are used. Average fertilizer rates for cotton over the United States are 80 kg N, 24 kg P and 35 kg K ha-'. These figures correspond to 6% of the N, 6.5% o f the P and 5.5% of the K used nationwide. When the amounts of nutrients used on the crops of sorghum and cotton are added to those used on corn, wheat and soybeans, nearly all the K, 89.5% of the P, b u t only 63% of the nitrogen is accounted for. Hay. Hay of many different types makes up a huge area of the United States. Although very sparse information is available, bermudagrass, alfalfa and clover-grass hay make up most of the 25 000 000 hectares. Few data are available a b o u t the rates o f fertilizer applied to hay crops, b u t it is a safe conclusion that most of it contains nitrogen and phosphorus. It is also safe to conclude that the average rate of fertilizer used is very low. As an estimate, perhaps 10% of the nitrogen and 5% of the P is used on hay. Other crops. A number of other crops are important locally in the United States. Examples are sugar beets, potatoes, vegetables, sugar cane, tree fruits and tobacco. While all of these enterprises oceupy small areas, they all receive rather high rates of fertilization, especially nitrogen. Tobacco, for example makes up only 5% of the cropland in Kentucky, yet uses 20% of the nitrogen. Although exact figures are n o t available, it is probable that most of the rest of the nitrogen is used on speciality crops. A last use of fertilizer (mostly nitrogen) is for home lawns. 6.10.4.2. Rates of fertilizer on a total land basis Because of the unevenness of cropping intensity in the United States, the rates of fertilizer on a total land area are quite different. Fig. 27 is a map of the United States showing rates of nitrogen on a total land basis. The states of Indiana, Illinois and Iowa have the highest use, followed by Nebraska,

206

Kansas, Ohio and Delaware. States with very low use are most of New England, West Virginia and most of the mountain states.

6.10.5. Nutrient inputs and outputs o f agricultural systems Since farming systems in the U.S. vary from monoculture row crops to livestock alone, with all combinations in between, it is meaningless to compute nutrient budgets for an average integrated farm with row crops, forage crops and livestock. The only hope of calculating nutrient budgets is to break down the farm into its separate parts and make the computation for pure monoculture systems. Once this is done, the monocultures can be put back together in any combination desired and the appropriate nutrient budgets computed. Thus, the approach here is to consider nutrient budgets for specific crops and livestock systems which are most important in the U.S.

6.10.5.1. Annual crops Agronomists have run many experiments designed to determine optimum fertilization rates and have determined rates and amounts of nutrient uptake by various agronomic crops under a wide range of conditions. Thus, the amounts of nutrients harvested with these crops at various yield levels are relatively well known for most crops. The American Potash Institute has been instrumental in compiling data of this type from various sources and Romaine (1965) gave average N, P and K contents of 35 crops at given yield levels. Although the values given are only averages, a survey of data from different areas of the U.S. on composition of corn shows remarkable similarity in composition of the harvested product (Jordan et al., 1950; Chandler, 1960; Barber, 1964). Similar composition from various areas was also true for soybeans (Hammond et al., 1951; Henderson and Kamprath, 1970). Thus, the average composition of seed crops, in particular, can be used reliably to calculate nutrient removals by crops. There are reasonably good data available from the U.S.D.A. on the application of fertilizer nutrients in particular areas to given crops and data on average yields of these crops. This information can be combined with average nutrient composition, and the amounts of harvested nutrients and fertilizer efficiency can be computed for any selected system. This approach has been used by various authors (Stanford et ah, 1960; Frink, 1969, 1970; Welch, 1972; Gilliam and Terry, 1973) to compute the potential for water pollution from fertilizer nutrients. The unfortunate aspect of this type of calculation is that only averages are obtained and, as pointed out before (Frink, 1971), there are very severe limitations to using averages for nutrient budgets. This is particularly true if one is using these average figures to predict pollution potentials, because averages for a system can indicate no problems when there are localized areas where problems exist. However, even with their limitations, average nutrient budgets serve very well to get the proper perspective, and so they will be used in the following discussion of particular crops.

Northern Indiana

N.E. Arkansas

Central Kansas

Kern Co., Calif.

Maine

Corn (grain)

Soybean (grain)

Wheat (grain)

Cotton

Potatoes

289637

35006.

1720 s

16803

67841

Yield (kg ha -1 )

1687

179'

34 s

see t e x t (p. 208)

1121

1017

14'

135

193

301

2077

--

--

373

651

804

794

364

904

852

104

134

74

104

152

P

1174

304

64

224

202

K

N

K

N

P

Nutrients harvested (kg ha -~)

Nutrients applied (kg ha -~)

I Average yields and average fertilizer nutrients applied f r o m Worden et al. (1971). 2 Based on data f r o m Indiana by Barber (1964). Data f r o m Strickland and Harwell (1971). 4 N u t r i e n t c o n t e n t f r o m R o m a i n e (1965). s Based on data f r o m Miller (1971). 6 Seed c o t t o n yields f r o m Table 9 in Pawson (1973). 7 Data f r o m Ibach and Adams (1968).

Area

Crop

Average nutrient inputs and nutrients harvested with representative i m p o r t a n t annual crops

T A B L E 69

88

1004

-2

see t e x t (p. 208)

27

N

Difference (kg ha -1 )

91

1

6

9

15

P

-6

15

45

90

-30

K

o

208

Corn. The estimated average nutrient input from fertilizer and nutrients harvested with corn grain in the northern two thirds of Indiana are shown in Table 69. Approximately one-third of the fertilizer N used in the U.S. is applied to corn, the largest concentration of corn is in the Midwest, and Indiana data are typical of this region. The average fertility of these soils tends to increase with respect to P and K under continuous corn even when the P and K lost via water removal is considered (nutrient losses in water will be discussed in a later section. However, much of this area is on a corn-soybean rotation and a lower percentage of the area planted to soybeans is fertilized. Thus the average P and K increases of the soils are smaller in a corn-soybean rotation then they would be in continuous corn. The range of N applied to give the average rate is much greater than the range of P and K rates. Annual fertilization rates of 200 kg N ha -~ are not uncommon. This has important implications with regard to N which can be lost to drainage water. Average N inputs minus N harvested with the crop for an area will underestimate the average loss of N to drainage water or through denitrification. This will be discussed in more detail later. Soybeans. As discussed above, there is less fertilizer applied to soybeans than to corn in the U.S. This is the result of the frequently observed lack of soybean yield response to fertilization in fertile soils (Chandler, 1960). The growth of soybeans results in a loss of P and K from soils to the harvested crop when they are not fertilized, and a slight increase in P and K in fertilized soybeans. The N story for soybeans is complex and interesting and may vary greatly from region to region in the U.S. It has generally been assumed that most of the N harvested in soybeans came from N fixed by the legume bacteria. However, a recent thought-provoking paper by Johnson et al. (1975) indicates that approximately half of the N harvested in soybeans in Illinois comes from the soil. They concluded that soybeans were good scavengers for inorganic N in soils. It has long been known that available nitrogen reduced symbiotic fixation of N by legumes (Allos and Bartholomew, 1955). Others (Schertz and Miller, 1972; Mathers et al., 1975) have proposed the use of alfalfa to remove inorganic N from soil to minimize leaching losses, but the idea that growth and harvest of soybeans would decrease total soil N is new. This seems very possible in soils like those of the Midwest which can supply a relatively high amount of N to a crop. However, in sandy soils of the Southeast, the net effect of growing soybeans is likely to be no change or an increase in soil N. For example, in North Carolina Henderson and Kamprath (1970) harvested 240 kg N ha -1 in soybeans and returned 47 kg N ha -1 to the soil in the unharvested plant parts. On the soil used, the a m o u n t of N returned to the soil in the plant is at least equal to, and probably greater than, the amount of mineralized N absorbed b y the plant during the growing season. It is apparent that the amount of N fixed b y soybeans is dependent

209 on soil N status; however, the accepted figure of 105 kg N ha -~ y-~ which is frequently cited (Porter, 1975) may be a good average.

Wheat. Wheat equals corn in area harvested, with the greatest concentration of wheat land in the Great Plains area. A typical average balance for this area is given in Table 69. However, it should be pointed o u t that in contrast to the average data from the Great Plains, in many other wheat areas o f the U.S. there are more fertilizer nutrients applied than are harvested with the crop. This is particularly true for N. Cotton. Cotton is produced in all of the southern states of the U.S. under a wide range of environmental conditions. These conditions range from nonirrigated dry land in Western Texas where 250 kg lint ha -~ is a good yield, to non-irrigated land in the Mississippi delta where 750 kg lint ha -~ is expected, to irrigated land in California where yields average near 1000 kg lint ha -~. The example for c o t t o n given in Table 69 is typical of crops in the irrigated west where both fertilizer inputs and expected yields are high. This poses a problem with regard to N pollution in waters leaching below these softs and in irrigation return flows. In the arid region soils, the native soil K is high and K is added in irrigation water. Thus the balance given shows a loss of K from the soft. This situation would also exist for many of the finer-textured c o t t o n softs of the Mississippi delta where no response to K fertilizer is expected. Potatoes. Potatoes are used in Table 69 t o serve as an example for vegetable crops. These crops are, almost without exception, very heavily fertilized and a relatively small percentage of the applied nutrients is harvested with the crop. Fertilizer cost is such a small fraction of the total cost of production that large amounts of fertilizers are applied in an a t t e m p t to get maximum yields. Although the values would be slightly different, a large number of high value crops could be used in the place of potatoes in Table 70. Soils which have a history of this t y p e of crop have very high contents of both total and available P and K and the potential for water contamination by N from production of these crops is very high. 6.10.5.2. Perennial crops Fertilized grazed bluegrass pasture. Typical fertilizer application to this t y p e of pasture in western North Carolina is 168--24--46 kg ha -1 y-~ of N, P and K, respectively. Unpublished data of Gilliam indicate that approximately 151--20--150 kg ha -~ y-~ of N, P and K may be harvested by the grazing cattle in the forage. However, at least 75% of the N and P and 85% of the K passes through the animal and is excreted back to the land (Peterson et al., 1956; Azevedo and Stout, 1974). This means that a net of only 38--5--23 kg ha -1 y-1 of N, P and K is removed as animal product. Under the above fertilizer regime, much of the P and K would be expected to accumulate in the soft because, as will be discussed later, only a small

210 percentage is removed in water. The nitrogen picture is much more complex, and good data are not available to determine accurately what happens to the difference between the 168 kg N added in fertilizer plus approximately 10 kg N added in the rain minus the 38 kg ha -1 net harvested as animal product. It has frequently been estimated that 50% of the nitrogen returned in the waste is lost by NH3 volatilization (Peterson et al., 1956; Stewart et al., 1975). This is a very crude estimate, however, as admitted in informal conversations with some of the authors of cited publications. A considerable amount of the N may be incorporated into the soil organic matter. This is particularly true if the land has previously been used for cultivated crops. Giddens et ah (1971) reported substantial increases in soil organic N for rescue sod following corn in Georgia. However, after a time, the soil will tend to establish a new equilibrium level of organic nitrogen. At this time, no reliable figures can be placed upon the distribution of N excreted as waste between NH3 volatilization, denitrification, and N accumulation in the soil organic matter. Forests. Nutrient cycling is much more quantitatively defined for forest ecosystems than for annual crops. There are several good publications (Cole et al., 1967; Young and Carpenter, 1967; Carter and White, 1971; Switzer and Nelson, 1975; Wells and Jorgensen, 1975) which n o t only describe the total N, P and K contained in the standing crop b u t also give the relative distribution within the various important parts of the tree. Some studies (Cole et ah, 1967; Switzer and Nelson, 1972; Wells and Jorgensen, 1975} also give the annual transfer of nutrients from the soil to the tree and loss from the tree via litter fall and leaf washing. However, here we will limit our discussion to accumulation in the tree and potential harvest of nutrients. The amounts of N, P and K contained in several tree species are given in Table 70. The differences noted in annual accumulation not only reflect differences between species b u t also soil differences. For example, Switzer and Nelson (1975) estimate that the annual N demand of natural stands of loblolly pine in Mississippi varies from 23 to 57 kg ha -1 y-I depending upon site characteristics and cultural treatment. The same ranges for P and K were 1.3--5.2 and 11--29, respectively. The amount of nutrients harvested with the tree is given in Table 71 and represents the minimum input for continuous tree culture. As shown in Table 70 there are considerably greater quantities of nutrients cycling within the forest ecosystem but this does not represent a transfer of nutrients from one system to another. The t y p e of harvest system will have a definite influence upon the amount of nutrients harvested with the tree. The a m o u n t of nutrients harvested per year of growth would be a maximum when the whole tree is harvested at a relatively early age for silage. As the age of stands increases, the likelihood that only the stem would be harvested increases. In a North Carolina stand at 16 years, the stems contained 45% of the N, 48% of the P and 54% of the K (Wells and Jorgenson, 1975). As the age of the stand increases, the proportion of elements in the stem as compared to vege-

Miss. Miss. N.C. Wash. Maine Ala.

Loblolly pine

Switzer and Nelson, 1972 Switzer and Nelson, 1972 Wells a n d J o r g e n s e n , 1 9 7 5 C o l e et al., 1 9 6 7 Young and Carpenter, 1967 Carter and White, 1971

Source

Cole et ai.,1967

Y o u n g and Caxpenter, 1967

Carter and White, 1971

Maine

Ala.

Wells and Jorgensen, 1975

Wash.

Switzer and Nelson, 1975

N.C.

Source

Miss.

Area

9

27

37

16

403

Age (years)

complete

stem

stem

stem

partial

Tree utilization

103 20 ~ 16 37 27 9

Age (years)

23

3.4

10.3

7.2

11.6

11

6

1.12

10

11.3

12

-6.6

9.2

--4.1

0.3

2.2

0.3

1.7

0.9

0.7

Hatvested

0.69 0.45 1.8 -0.4 -0

Hatvested

Fron, soil I

0.9 0.9 1.9 6.6 0.9 2.2

P Rain input

7.5 6.2 19 12 -0

N

8.5 8.7 16 24 8.3 23

4.9 4.9 10.3 14.4 3.5 17.8

Tops

K

0.3

0.1

2

0.3

0.3

Rain input (kg ha -~ y - l )

Tops Forest floor ( k g h a -1 y - l )

Tops

Forest floor

P

N

1.9

0

1.7

0.6

0.4

From soil I

1.2 0.8 1.7 5.3 -0

Forest floor

17.8

1.6

10.5

5.6

7.3

Hatvested

K

4.0

3.0

0.82

4.0

4.0

Rain input

13.8

2.4

9.7

1.6

3.3

From soil 1

i These figures assume no loss by leaching or surface run-off which is obviously incorrect. The a m o u n t lost via these mechanisms would have to be added to the figure shown, Estimates for leaching in Miss. were 8.7, 0.6 and 2.7 kg ha -I y - l for N, P and K, respectively. Esthnate$ for Wash. were 0.6, 0.02 and 1 kg ha -I y-1. 2 These figures seem low to the authors of this publication but were included as estimates in the paper f r o m which the tree data were obtained. SThe data in Table 71 are f r o m a more productive site in Miss. than the data in Table 70.

Douglas fir White birch Cottonwood

Lobloliy pine Loblolly pine

Tree

Nutrients harvested annually with trees and sdurces of nutrients

TABLE 71

Loblolly pine D o u g l a s fir White birch Cottonwood

Area

Species

A n n u a l n u t r i e n t a c c u m u l a t i o n in r e p r e s e n t a t i v e f o r e s t s o f t h e U . S .

T A B L E 70

tO ~=~

212

tative parts increases. However, the annual rates of nutrient harvest would d e c r e ~ e with age because accumulation rates also decrease with age. The estimated annual demand from the soil in Table 71 assumes that no nutrients leave the forest ecosystem except by tree harvest. As will be discussed later in this paper, the amounts of N, P and K lost to runoff water are low when compared to losses from cultivated fields. However, when compared to annual demand b y the harvested crop, they are significant. For example, Switzer and Nelson (1975) estimated that 4.3 kg N ha -1 y-~ leached from their system and the annual accumulation in the harvested product was 11.6 kg N ha -I y-l.

6.10.5.3. Livestock systems The average annual inputs of N, P and K to selected livestock systems are shown in Table 72. Also shown are the amounts of these elements which are harvested with the respective products and the amounts excreted as manure. The data in this Table were obtained by computing the N, P and K fed in commercial agricultural enterprises in California, the average production and the average elemental content of the product and using the difference as being excreted as waste (Branson et al., 1973). Yeck et al. (1975) used a similar approach for N and obtained reasonably comparable values. The values are also close to those reported by Weber et al. (1968) who based their data upon amounts and composition of manure excreted. However, the variations encountered in published data are considerable and the data reported in Table 72 should be considered only as reasonable approximations. The data in Table 72 showing amounts of elements per animal excreted in manure can be combined with animal numbers for any sized system to c o m p u t e the amounts of elements contained in the waste. Computations of this t y p e have been made for the U.S. (Stewart et al., 1975) and for various areas of the midwestern U.S. (Midwest Plan Service, 1975). As will be discussed in more detail later, much of the P and K excreted b y the various animals is returned to the land as manure. However, much of the nitrogen is lost to the atmosphere as ammonia or through denitrification before it can be incorporated into the soil. There have been very few nutrient budgets calculated for integrated cropanimal systems where the efficiency of the utilization of the elements excreted in the manure is considered. Frink (1969, 1970) made calculations of this type for dairy farms in Connecticut (Table 73). His data indicate that only 16, 15 and 21% of the input N, P and K respectively were exported as product. It is interesting to compare these efficiencies with those calculated for dairy farms where only feed inputs were considered and no utilization of the manure was considered (Table 72). The efficiency of utilization of N, P and K in this system was 27, 28 and 6%, respectively. Thus with regard to efficiency of utilization of input N and P, the integrated crop-dairy animal system is less efficient than a dairy system where no consideration is given to efficiency of feed production or utilization of N and P in waste. It should be

11

39

0.43 0.27 0.83 2.6

12

56

0.82 1.10 2.12 8.7

46

166

0.39 0.83 1.29 6.1

28

44

120

0.21 0.27 0.52 1.80

5

8

28

0.09 0.03 0.15 0.28

3

3

8

Product

Intake

Excreted

Intake

Product

P (kg per head)

N (kg per head)

0.12 0.24 0.47 1.53

2

5

20

Excreted

0.20 0.29 0.53 1.94

26

21

118

Intake

0.04 0.02 0.06 0.19

1

1

12

Product

K (kg per head)

0.16 0.27 0.47 1.75

25

20

106

Excreted

1 Computations made from data contained in Weber et al. (1968), Salter and Schollenberger (1939) and Yeck et al. (1975).

Dairy cows Beef (225-475 kg) Beef (113-244 kg) Chickens Broilers Layers Turkeys Market hogs I

Class of livestock

Annual N, P and K balances for livestock systems (data, except hogs, from Branson et al., 1973)

TABLE 72

~o

214

T A B L E 73 N u t r i e n t b u d g e t s for dairy farms in C o n n e c t i c u t (after Frink, 1969) N

Input Feed Fertilizer Fixation Rainfall Total Output Milk Meat Total Difference (Input - Output)

P K (kg c o w -1 y - l )

81 50 90 4 225

18 22 --40

20 42 --62

31 5 36

5 1 6

8 1 9

189

34

51

noted that if the two systems are compared only with regard to imported N (N fixed by legumes and N in rain ignored), the N efficiency of the t w o systems is nearly identical. Frink (1971) noted a relatively large effect of farm size upon the efficiency of conversion of imported N into exported protein N. When the Connecticut farms had only 0.5 ha of land per cow, the efficiency of utilization was approximately 26%. When land area per c o w increased to 1 ha, the efficiency increased to approximately 40%. These large differences were attributed to high rates of N applied to crops on farms with smaller land area per cow in ~ttempts to get maximum production or to dispose of manure. 6.10.6. Nutrient losses via water and air

Quantitative estimates of nutrients lost from agricultural systems via water and/or air involve more assumptions and are less accurate than estimates of nutrient inputs and crop removal. Certainly, significant amounts of all three elements are removed with erosion losses from soils. Walker and Wadleigh (1968) estimated that the Mississippi River which drains 317 million ha of land carries approximately 450 million metric tons of sediment annually to the Gulf. It is simple to c o m p u t e an average yearly loss of 1.4 tons ha -1 of sediment; however, this average is almost meaningless because the range in annual sediment loss is from 0.03 to 96 tons ha -1 (Ursic, 1963). Much of the sediment loss to water is from cultivated lands which are the most fertile. The recent emphasis on water quality has resulted in a large a m o u n t of research designed to determine more accurately the quantities of nutrients lost under various situations. This is true particularly for N and P which are

215

generally considered to be of more environmental concern. However, as we hope to make clear in the following discussion, there are still large gaps in our knowledge. Nitrogen is especially a problem because significant amounts can be lost from the system via a great many pathways. Because the differences between elements are more significant than the differences between agricultural systems, the following discussion is by element rather than by t y p e of system.

6.10.6.1. Nitrogen There are very few agricultural systems in North America where N is accumulating in the soil. It is well d o c u m e n t e d that large amounts of N and organic matter have been lost from our soils as a result of cultivation of native grasslands. Although a plot of nitrogen loss vs. time shows that we are near steady state or are asymptotically approaching zero loss from soils, it is probable that a small net loss of nitrogen from cultivated soils is still occurring. If this basic assumption is accepted, then nitrogen lost from agricultural systems will be equal to or slightly greater than the N input. This means that in N-fertilized systems, the fertilizer N immobilized b y soil bacteria will be approximately equal to organic soil N mineralized. This assumption can be justified and greatly simplifies N balance considerations because mineralization and immobilization then do not have to be considered even though it is recognized that they are important soil processes. Previous sections discussed N removal with the harvested products and this section will be concerned with the fate of the unutilized nitrogen. As pointed out by Keeney and Walsh (1972) in a review article, this topic has been reviewed recently in at least ten different books, papers and symposia. 6.10.6.1.1. Nitrogen lost to surface waters Cultivated crops. Some examples of recent measurements of nitrogen losses from cultivated crops to waters are given in Table 74. These data are n o t :~tended to be a complete list of available data nor were they selected to give examples of extremes measured. However, they do indicate the range of values recently seen in the literature. One problem with evaluating literature values for an overview such as we are attempting is the non-uniform methods of measurement made b y different investigators. Some (Bolton et al., 1970) measured only the NO3-N removed b y tile drains and made no measurements of losses by surface runoff. Others (Keeney, 1973) made no measurement of organic nitrogen in surface runoff and some (Schuman et al., 1973) have only measured losses b y surface runoff. Most of the nitrogen removed by surface runoff is organic nitrogen associated with the sediment. It is possible to get significant losses of inorganic nitrogen in surface runoff if heavy rains immediately follow a surface application of fertilizer to a soil (Moe et al., 1967; Kilmer et al., 1974) b u t this mechanism of loss accounts for a small proportion of N loss from softs or of the fertilizer N applied. Viets (1971) has suggested that application of N

1Only inorganic N considered.

New Hampshire West Virginia Connecticut North Carolina Oklahoma Ontario, Canada Ontario, Canada Ontario, Canada Idaho Iowa Iowa Iowa North Carolina Oklahoma Oklahoma New York California

B o r m a n e t al., 1968 Aubertin and Patric, 1974 Frink, 1967 K i l m e r e t al., 1 9 7 4 O l n e s s e t al., 1 9 7 5 B o l t o n et al., 1 9 7 0 B o l t o n et al., 1 9 7 0 Nicholls and MacCrimmon, C a r t e r e t al., 1 9 7 1 S c h u m a n e t al., 1 9 7 3 Hanway and Laflen, 1974 B a k e r e t al., 1 9 7 5 G a m b r e l l e t al., 1 9 7 5 a , b O l n e s s e t al., 1 9 7 5 O l n e s s et al., 1 9 7 5 Jones and Zwerman, 1972 B i n g h a m e t al., 1 9 7 1 1974

Geographical area

Source

forest forest forest pasture pasture corn oats, alfalfa mixed mixed corn corn corn corn irr. c o t t o n wheat corn, wheat citrus

Crop

----23 3' -25 13 6 ---

Surface drainage

15 9 -33 -6 31 21 -. 18 64

.

Subsurface drainage

Loss (kg ha-' y-' )

Examples of nitrogen loss to surface waters from forest, pasture and cultivated lands

TABLE 74

.

-

--

-

1.8 0.8 3.4 8 6 --4 --9 -46 -.

Total

11--73 --

3--12 2--10 ----3--40 0.1--22 2--62 45--48 --

Range measured

t,~

217

fertilizers might even reduce the amount of N lost by surface runoff b y promoting a good ground cover, b u t application of N fertilizer will also tend to maintain the soil organic matter content at a higher level so that similar sediment losses will result in more organic nitrogen losses from the fertilized soils. This has been observed in North Carolina (Gambrell et al., 1975b). The availability of the organic N lost to the aquatic ecosystem in the receiving waters, and the ultimate fate of the N are poorly u n d e r s t o o d (Keeney, 1973). The N certainly can cause problems b u t it is less of a eutrophication problem than entry of inorganic N into the same system. The range of NO3-N reaching surface waters via tile drains or subsurface flow is very large as seen in Table 74. Hanway and Laflen {1974) reported that some of the tile drains that they monitored in fertilized corn fields contained essentially no nitrate. We (Gambrell et al., 1975a, b) have similar observations in North Carolina on some soils. However, there are other fields with similar management where large amounts of NO3-N are removed via subsurface drainage. The difference, as will be discussed later, is probably due to denitrification. The rate of fertilizer nitrogen applied definitely has an influence upon quantities of NO3-N leaving the field via subsurface water in many fields. Obviously the lower the percentage of applied N harvested with the crop, the greater the amount available for leaching. This effect upon the a m o u n t of N lost to water has been observed by several investigators (Bolton et al., 1970; Jones and Zwerman, 1972). One problem with using average N application rates and average N availability for leaching to calculate the water contamination is that the relationship between application rate and N availability for leaching is n o t linear. For example, there would be more N lost from the system via water or air if one field received no N and a similar field had a rate of 200 kg ha- 1 than there would be if both fields received a rate of 100 kg ha- 1. Thus the difference between average applied N and average product N shown in Table 69, underestimates the potential N delivered to water. Streams draining areas of intensive fertilizer use frequently do n o t reflect any differences in NO3-N content when compared to other streams in the same region where little fertilizer is used or to concentrations in the same stream measured many years before large amounts of fertilizer N were used (Bower and Wilcox, 1969; Thomas and Crutch field, 1974). In North Carolina, we have observed (unpublished data of Gilliam) that concentrations of NO3-N in native streams draining from areas with high concentrations of well drained cultivated soils where the tile drainage waters contain 15--20 mg NO3-N liter -1 are essentially the same as the concentrations in streams from poorly drained soils where the field drains contain very little NO3-N. There seems to be no d o u b t that fertilizer use on cultivated crops and intensive agriculture increases the input of nitrogen into surface waters. However, the magnitude of this increase and the effect that this may have upon nitrogen concentrations or biological activity in streams of the region is much less clear.

218

Forage crops. The amount of unharvested nitrogen leaving land used for forage crop production has been of much less concern and thus has received less attention. This is a result of higher percentages of applied nitrogen being harvested with the crop, less sediment loss from fields in forages and the quantities of N applied to forages being small in relation to other crops. Kilmer et al. ( 1 9 7 4 ) f o u n d an annual average of 12 kg ha -1 in drainage water leaving a fertilized bluegrass watershed in North Carolina. A similar unfertilized watershed lost 3 kg ha -1. Essentially all of the nitrogen lost was in the nitrate form from both watersheds. In the bluegrass region of Central Kentucky, Thomas and Crutchfield (1974) found much higher annual losses of NO3-N (approximately 25 kg ha-l). The high fertility of these soils probably accounts for this, since little fertilizer is used. Olness et al. (1975) reported annual losses of 2 and 10 kg ha -1 of N from t w o grazed rangeland watersheds in Oklahoma. In contrast to the North Carolina data, most of the N lost from the Oklahoma watersheds was organic N. These Oklahoma authors point o u t that the average N lost from the t w o grazed watersheds was approximately equal to the amount of N entering the watersheds in rain. Forests. The N lost to drainage waters from forested land represents the minimum loss for a particular soft or region for many reasons. There is a minimum of soft loss by erosion from forests, and in the majority o f forests, N is a growth-limiting factor. Thus, there is little inorganic N present under normal conditions. Also, much of the inorganic N present is in the reduced form which does not move as readily with percolating water as nitrate. Most work has shown that forests are N-accumulating systems in that more N is added in rain than is lost in water. Recent measurements of kg N ha -~ lost annually to surface waters have measured a range of 0.8--3.4 (Table 74). Although these values are from unfertilized forests and fertilization of forests is increasing slightly (Pritchett and Smith, 1975) work in North Carolina by Sanderford (personal communication, 1975) has detected no difference in N contents of water draining from a pine forest before and after fertilization. Animal systems. Although a large amount of research on the topic of pollution effects of animal waste is currently in progress in the U.S., there is absolutely no way that anyone can make an accurate quantitative estimate of N reaching surface water from animal wastes. Nitrogen in r u n o f f water from large beef feedlots in Nebraska has been measured (Gilbertson et al., 1970; McCalla et al., 1972) and values of 3--6% of the amount excreted were reported. Robbins et al. (1971) reported that 3% of the N defecated b y hogs on dry lots in North Carolina was found in a stream draining the area. These authors concluded that even where swine were raised on dry lots very poorly located with respect to streams, less than 10% of the waste would be removed with the drainage water. Although the above-quoted figures seem relatively quantitative, t h e y are by no means the whole story. Waste from animals fed in confinement must still be disposed of in some manner. Even after the manure is applied to the land which serves as the terminal acceptor of most animal waste, there is still

219 a danger of loss of N b y surface runoff before the N becomes incorporated with the soil. It is well recognized that manure applied to frozen soils is subject to runoff losses (Midgley and Dunklee, 1945; Stewart, 1970), and this practice is discouraged throughout the U.S. However, a significant amount of N applied in manure even during the warm season may be lost (Midgley and Dunklee, 1945) via surface runoff. Another problem leading to greater losses of N from manures to water is that many animal production units have very limited land. In the past this frequently has led to very high rates of manure application to land for disposal. These high rates invariably lead to a much higher loss of the N applied in the manure to water. The recent increase in fertilizer nitrogen prices has changed ideas with regard to manure disposal and N utilization. Before the price increases, manure was usually considered only a disposal problem. Now more farmers are interested in getting maximum utilization of the nutrients contained in the manure. This interest will lead to better management practices and consequently to less N lost to drainage waters. The above discussion is not intended to be either quantitative nor a complete description of the problem of animal waste and water quality. This has been the topic of many recent books and symposia and there are still very many unanswered questions. However, with the large a m o u n t of manpower and research m o n e y currently being spent on this problem, more definitive answers will soon be forthcoming.

6.10.6.1.2. Nitrogen lost to groundwater In spite of the large number of studies designed to determine the threat of groundwater contamination by NO3 from agricultural sources, there are very few areas where an accurate quantitative prediction can be made of the NO3 moving to groundwater. This is because there is currently no accurate way of quantifying denitrification under the wide range of soil conditions encountered within most regions. Almost everyone agrees that N is not accumulating in the soil, so total N input minus N in harvested crops minus N loss to surface water will equal N lost by denitrification plus N moving to deeper groundwater. It is the distribution between the latter two components which can be estimated only very crudely in most situations. As pointed out b y Viets (1974) in a discussion of denitrification, "We do not have balance sheets of nitrogen inputs and outputs in any situation". In some regions of the U.S. there is no apparent threat to deeper groundwater by the leaching of nitrate. In the Atlantic coastal region, Gilliam et al. (1974) in North Carolina, Peele and Gillingham (1972) in South Carolina, and Gillings (1973) in New Jersey have observed significant movement of fertilizer nitrogen applied to cultivated crops to shallow groundwater. However, the water tables in this region are relatively shallow and there seems to be little m o v e m e n t of nitrate from shallow to deeper groundwater. In North Carolina we have found that the lack of significant concentrations of nitrate in deeper groundwater is a result of several factors. There is only a small

220 a m o u n t of water movement downward in most areas due to nearly impermeable aquatards in the profile, and so most water movement is horizontal toward a stream. Also, much of the nitrate is reduced in the shallow groundwater in the field area. The fate of nitrate moving horizontally with the shallow groundwater is unknown. Gilliam et al. (1974) have speculated that much of it may be lost by denitrification under certain conditions in the lowland area where the water seeps to the land surface. Presumably the above factors are present in much of the southeastern U.S. Coastal Plain to prevent any significant nitrate concentration in deeper groundwater as a result of normal agricultural activity. In the hilly to mountainous portions of the Southeast, there is generally no true groundwater. Underground streams break out as springs and thereby contribute directly to surface water contamination. Values of NO3-N range from 0 to 6 p p m depending largely on the geology of the region. The high values are associated with limestone (Thomas and Crutchfield, 1974). In the midwestern U.S., significant amounts of nitrate have been found in transit between soil rooting zones and the groundwater. Gast et al. (1974) found in the soil profile from 14 to 50% of unutilized fertilizer N applied to corn on t w o soils over a period of 13 years. These authors presented evidence to show that the remainder was lost b y denitrification. Gentzsch et al. (1974) reported that the NO3-N content below the rooting zone in central Illinois was related to soil characteristics and agricultural activity. In poorly drained soils or soils with natric horizons, there was very little nitrate found below the rooting zone. In all other soils, the a m o u n t of nitrate found below the rooting zone was related to amount of fertilizer used or animal activity. Similar observations have also been made in Missouri (Linville and Smith, 1971) and Wisconsin (Olsen et al., 1970). Results similar to those in the midwestern states have also been made for the Great Plains and R o c k y Mountain areas. Although the fertilizer usage is much less per unit land area in the Plains region as compared to the Midwest, there are still areas of the Plains states where significant amounts of nitrate have been found moving below cultivated fields or feedlots. Stewart et al. (1967, 1972) sampled a number of sites in Colorado and reported the following averages of NO3-N in the profile: virgin grassland, 100 kg ha -1 ; dryland farming, 292 kg ha-l; irrigated farming, 566 kg ha-~; and feedlots, 1630 kg ha -~. Somewhat similar results have been reported from Kansas (Murphy and Gosch, 1972), Nebraska (Herron et al., 1968) and North Dakota (Power, 1970). These reports are also similar to the data from the Midwest where a variable b u t significant amount of the unutilized fertilizer or animal waste N could n o t be found and was presumed to be lost b y denitrification. The problem of leaching of nitrate to groundwater is greater in the irrigated areas of the western U.S. than in any other place in North America. There have been a number of investigations in California (Stout and Burau, 1967; Adriano et al., 1972 a,b; Nightingale, 1972; Pratt and Adriano, 1973; Lund et al., 1974), which have reported large amounts of nitrate between topsoils

221

and the underlying groundwater. One reason for the larger amounts of nitrogen found below the rooting zone in much of this region is that use of fertilizer is greater per unit area for the irrigated crops and much of the land utilized for agriculture is in crops which receive heavy applications of fertilizer regardless of the region where grown. Another reason is the lack of water for dilution. An example of the heavy fertilizer use and leaching loss is given b y Pratt and Adriano (1973) who reported losses of N from nine miscellaneous row crops ranging from 47 to 912 kg N ha -~ y-~ in southern California. However, these authors estimated that denitrification accounted for from 0 to 256 kg ha -~ y-1 of the N losses. As in other areas of the U.S., the amount of denitrification is related to known profile characteristics (Lund et al., 1974) b u t is very difficult to predict for all field situations. The estimated values may range from near zero percent reported b y Pratt and Adriano (1973) for some fields, to nearly 100% of the leached nitrates reported by Meek et al. (1969) in the Imperial Valley of California. In some areas of California, the concentration of dairy and other animals is so high that much concern is expressed a b o u t the leaching of nitrate and other ions from the excreted waste to the groundwater. Many of the data in Table 72 were compiled as a result of this concern. Consideration has been given to limiting the concentration of animals, based on the threat of movement of nitrate and other contaminants to groundwater, b u t no regulations have been passed. 6.10.6.1.3. Nitrogen lost to air The soil factors affecting the rate of denitrification are well k n o w n and there is currently a large amount of research effort directed toward soil denitrification investigations. However, personal conversations with a large percentage of these investigators in the last year have revealed that none is confident of accurately quantitatively estimating denitrification in most field situations. The extremes where little or no denitrification takes place or nearly all of the nitrate formed is lost b y denitrification are easy to predict. However, most soils are between these extremes and pose difficulty with regard to quantitative estimation. In the previous section, several examples were given of field estimates of denitrification obtained b y difference. These values ranged from zero to 100% of the unharvested fertilizer nitrogen applied. Nearly all of the direct measurements of denitrification have been conducted under laboratory or greenhouse conditions. Nitrogen recoveries in greenhouse crops and soil using ~SN-tagged sources range from 53 to 100% of the added N with an average reported loss of about 15% of the N (Hauck, 1969). Thus, the figure of 15% of the added N lost b y denitrification is very frequently used in computations o f N balances. In a recent informal meeting in the U.S. of researchers from the Southeast, Midwest and Far West who are working with denitrification, the figures of 10--15% were generally accepted as being as accurate as any. This would indicate that 10--20 kg N ha -~ of

222 cultivated land is lost through denitrification. These figures are obtained b y crude extrapolation of data such as those obtained in North Carolina (Gambrell et al., 1975 a,b). We measured essentially no denitrification on one moderately well drained soil and as much as 60 kg ha -1 on a poorly drained soil. It is obvious from available data that the amount of denitrification in softs is inversely related to drainage and directly related to the presence o f soil horizons which restrict water movement. It is also inversely related to such factors as proportion of the percolating water intercepted by artificial drains, as indicated by water below the drains containing a lower concentration o f nitrate than the water in the tile drain (Gilliam et al., 1974; Thomas and Barfield, 1974). The current knowledge of how to investigate all of the factors affecting denitrification in field situations is so limited that we are seemingly forced to accept the crude estimate of losses of 10--20 kg ha -1 y-l. The amount of nitrogen lost from animal waste during storage, treatment and handling has been estimated b y Vanderholm (1973) to range from 34 to 84% depending upon the treatment system used. Much of this N is lost as ammonia and very significant concentrations of ammonia have been measured in the atmosphere in the vicinity of large concentrations o f animals (Stewart, 1970; Luebs et al., 1973). Also, some of the nitrogen is oxidized to nitrate and then lost through denitrification. However, measurements of losses of nitrogen from manure from different farms under apparently similar conditions have been extremely variable. Thus, a figure of 50% of the excreted N being lost during handling and storage is usually used, although it is recognized that this is a very crude estimate (Stewart et al., 1975).

6.10.6.2. Phosphorus 6.10.6.2.1. Phosphorus lost to surface waters The concern about the contribution of P from agricultural sources to the eutrophication of surface waters has resulted in considerable attention to losses of P to drainage waters over the past few years. As pointed o u t b y Viers (1970), agronomists had not previously been concerned a b o u t loss of the very small amounts of P such as the 10--15 ppb in water (Sawyer, 1947; Luckey, 1961) necessary to get good algal growth. Since the increase in the awareness of the possibility of a problem, there have been several review articles (Stanford et al., 1960; Taylor, 1967; Holt et al., 1970; Ryder et al., 1973) summarizing the known information about P losses from soils. The review by Ryder et al. {1973) is thorough and a good overview of the current knowledge. Only a very small amount of P is lost apart from that lost with the eroding sediment. Since forested soils are usually low in fertility and erosion is low, the losses of P from forested watersheds are quite small (Table 75). The losses from range land and/or grazed forage watersheds are larger than from forested land b u t still quite low when viewed from a soil nutrient balance standpoint. The amounts of P lost from cultivated soils are extremely variable, as

New Hampshire Minnesota West Virginia Ontario, Canada Oklahoma N o r t h Carolina Iowa Oklahoma Michigan Iowa Indiana Alabama Ontario, Canada

Borman et al., 1968 Singer and Rust, 1975 Aubertin and Patric, 1974 Campbell and Webber, 1969 Olness et al., 1975 Kilmer et al., 1974 Hanway and Laflen, 1974 Olness et ah, 1975 Erickson and Ellis, 1971 S c h u m a n et al., 1973 Nelson, 1973 Scarseth and Chandler, 1938 Bolton et al.~ 1970

forest forest forest pasture pasture pasture cultivated cultivated cultivated cultivated fallow cultivated cultivated

Crop

1.06

Surface drainage

0.15

0.04

Subsurface drainage

Loss (kg ha -1 y - l )

0.02 0.09 0.12 0.08 2.9 0.21 1.10 5.5 1.0 0.7 6. 41 60 i

Total

1 These values o b t a i n e d in plot w o r k and all of the P n o t delivered to stream due to redeposition.

Geographical area

Source

Examples of phosphorus loss to surface waters f r o m forest, pasture and cultivated watersheds

T A B L E 75

----1.3--4.6 0.15--0.27 0.09--2.55 1.3--11.2 0.8--1.3 0.5--2.1 -_ 0.08--0.24

Range measured

tO b~ CO

224

illustrated in Table 75. Several authors have concluded that an average value for loss of P from cultivated lands is a useless number because of the tremendous variation between different fields and management systems. However, a large number of recent measurements have been in the range of 1--4 kg P ha-1 y-l, although one suspects that a large percentage of these measurements was not made in soils which are marginal for cultivated crops where erosion and thus P loss is the greatest. As stated earlier, when large losses of P are encountered, they are associated with large losses of sediment. There is a very good correlation between P loss and sediment loss on cultivated soils (Romkens et al., 1973). However, from a water pollution standpoint, there is a significant amount of P lost from fertilized, cultivated soils in the soluble form. Surface runoff water has been found to equilibrate rather rapidly with the surface soil so that the P concentration in the water is near the concentration in an equilibrium extract from the soil (Romkens et al., 1973). Thus a concentration of 200 ppb in solution of the water from fertile or recently fertilized soils is not u n c o m m o n (Nelson, 1973). Although an annual surface r u n o f f of 25 cm with concentration of 200 ppb would only remove approximately 0.5 kg P ha -1, this is above the concentration reported necessary for good algal growth (Luckey, 1961). It is true that this runoff water will be diluted b y runoff water from forested or grassed areas which have lower P concentrations. However, a share of the sediment carried b y the streams in agricultural areas is from the cultivated and more highly fertile soils. This sediment will tend to reach a new equilibrium with the water so that the concentration will be higher than the P concentration in the water from uncultivated areas and lower than the P concentration from the cultivated areas. Another complicating factor is that the sediment from the stream bank, etc. m a y have a high P absorptive capacity and reduce the equilibrium P concentration. This effect has been noted b y Kunishi et al. (1972). There is no d o u b t that fertilization of soils will increase the P lost to surface r u n o f f waters because the equilibrium P concentration may be increased as much as ten-fold (Baldovinos and Thomas, 1967) and the sediment lost by erosion will contain more P. If loss of P from cultivated soils is a significant problem with regard to water quality, this is going to be very difficult to control because it is difficult to conceive of reducing sediment loss to levels which would significantly reduce the equilibrium P concentration of the sediment with the drainage water. No mention has been made of loss of P to groundwater. Although obviously some P is lost by this pathway, the amounts are so small, except in unusual circumstances, from both a water quality and an agronomic viewpoint that they are insignificant. The quantities of P lost to drainage water from animal waste are significant under some conditions. As discussed in the nitrogen section, 3--10% o f the defecated waste may be lost via surface r u n o f f from some beef, dairy and hog operations. In the Midwest, much of the manure from cattle and hog opera-

New Hampshire West Virginia North Carolina Ontario, Canada Ontario, Canada Michigan Illinois Virginia

Borman and Likens, 1970 Aubertin and Patric, 1974 Kilmer et al., 1974 Bolton et al., 1970 Bolton et al., 1970 Erickson and Ellis, 1971 Kurtz, 1970 Rogers, 1941

forest forest pasture pasture cultivated cultivated cultivated cultivated

Crop

2831

Surface drainage

15

0.34 1.0

Subsurface drainage

Loss (kg ha "1 y - l )

Ii

1.7 2.7 4.9

Total

100"-5731

0.10--0.6 0.4--1.5 2--26

Range measured

1These values are for cultivated soil on slopes ranging from 5 to 25% where erosion removed 9 to 40 tons topsoil per ha, and represent the total K lost from plots. The other values given in this table represent only soluble or exchangeable K removed by water.

Geographical area

Source

Examples of potassium lost to surface waters from forest, pasture and cultivated watershed

TABLE 76

t~ t~ O1

226 tions is stored during the winter in lagoons and as much as 50% of the P may remain as sludge in the lagoon (Midwest Plan Service, 1975). With most other livestock operations, however, a large percentage of the P will eventually be returned to the land with the eventual result being essentially the same as if equal quantities of inorganic P fertilizer were added. 6.10.6.3. Potassium 6.10.6.3.1. Potassium lost to drainage waters The loss of K from agricultural systems has not received nearly as much attention in the past few years as the loss of N and P because there are no known problems caused by presence of K in waters with the exception of its minor contribution to excessive salts in some waters in the western states of the U.S. and Mexico. Even in the studies where loss of K has been measured, it has usually been a rather incidental measurement where N and P were of primary interest. Many of the estimates of leaching losses of K are based on old lysimeter work (Kurtz, 1970) and there has been little improvement on the estimates of average losses of 10--15 kg ha-' y - ' made by Truog and Jones (1938) (Table 76). Most of the recent measurements of K losses have been through tile drains or as soluble and exchangeable K in surface runoff. The total K losses reported would be much larger if the K incorporated in the mineral structure of the eroded material were included. Much of the most informative data on the fate of nutrients excreted in animal waste has come as a result of the environmental concern of the past few years. Since K has not been of environmental concern, few data have been obtained for K. The only exception to this is the potassium contained in chicken manure which has frequently caused animal problems when the waste was applied at high rates to forages. Considerable research on this topic has been conducted b y the research group of U.S.D.A.--A.R.S. at Wakinsville, Georgia. Essentially all of the K excreted b y poultry is applied to soils. Losses of potassium excreted b y other animals to waters would be similar to those of P except that more K would be leached toward the groundwater. We (Overcash et al., 1976) have found that approximately 25% of the K entering swine waste lagoons in North Carolina settled in the sludge and was not removed in the effluent. 6.10.7. Nutrient balances Classification. Eight nutrient balances were prepared as follows: Intensive arable. Reference: Thomas + Gilliam-1; corn for grain, northern Indiana, U.S.A., Table 77. Intensive arable. Reference: Thomas + Gilliam-2; soybeans for grain, northeastern Arkansas, U.S.A., Table 78. Intensive arable. Reference: Thomas + GiUiam-3; wheat, central Kansas, U.S.A., Table 79.

227 Intensive arable. Reference: Thomas + Gilliam-4; Irish potatoes, Maine, U.S.A., Table 80. Intensive arable. Reference: Thomas + Gilliam-5; cotton, California, U.S.A., Table 81. Intensive livestock. Reference: Thomas + Gilliam-6; grazed bluegrass, western north-California, U.S.A., Table 82. Extensive forestry. Reference: Thomas + Gilliam-7; loblolly pine, 40 years, Mississippi, U.S.A., Table 83. Extensive forestry. Reference: Thomas + Gilliam-8; Douglas fir, 37 years, Washington, U.S.A., Table 84.

Method of computation of nutrient flows of selected agro-ecosystems The data used in Tables 77--84 are mainly derived from sections 6.10.4-6.10.6. In particular, the following references were used:

Corn, soybeans, wheat, potatoes and cotton. The average composition of seed crops, which could be derived from the data of the authors mentioned in 6.10.5. was used to calculate nutrient removals by crops. There are reasonably good data available from the U.S.D.A. on the application of fertilizer nutrients in particular areas to given crops and data on average yields of these crops (Worden et al., 1971; Strickland and Harwell, 1971; Miller, 1971; Pawsen, 1973). This information was combined with the average nutrient composition of crops to obtain nutrients harvested with selected crops in a given year. The mineralization of soil organic fraction was estimated using data in Ibach and Adams (1968) giving yields when no fertilizer was used. The nutrients lost via water or air were estimated using data from a large number of research reports for the United States. These reports are listed in the bibliography.

Grazed bluegrass. The applied nutrients lost via surface runoff and the nutrients taken up by the grass are experimental values of Gilliam in cooperation with workers at Tennessee Valley Authority (Kil.mer et al., 1974). The nutrients passing through the animal as manure were based on reports by Peterson et al. (1956) and Azevedo and Stout (1974) that 75% of the N and P and 85% of the K passes through the animal and is excreted to the land. Other values were estimated or obtained by differences. Loblolly pine, Douglas fir. The data for the loblolly pine were taken from research by Switzer and Nelson (1972, 1975). A paper by Cole et al. (1967) provided the basic information for Douglas fir.

228

T A B L E 77 System type: Intensive arable

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -~ y - l )

T y p e o f farm or e c o s y s t e m or t y p e o f part o f a f a r m o r e c o s y s t e m , ref. n o . T h o m a s a n d G i l l i a m - 1

Corn for grain, N o r t h e r n Indiana, U.S.A.

Nutrient

N

P

K

-126

-22 ---

-111

--85 41 -126

--15 7 -22

--20 91 -111

0

0

0

Changes in a m o u n t of p l a n t c o m p o n e n t SUPPLIES:

29. 30t. 30r. 31.

Input by Transfer Transfer Input by

seeds or seedlings ............... by net uptake from soil ........... b y n e t u ~ t a k e f r o m soil . . . . . . . . . . . uptake trom atmosphere .......... TOTAL

REMOVALS:

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by plant production remaining on field . Transfer by seed for sowing .............. TOTAL SUPPLIES-REMOVALS

Changes in a m o u n t o f animal c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4.

Input by Input by Transfer Transfer

5. 6.

Output by animal products ............... O u t p u t b y l o s s e s f r o m m a n u r e t o air, b e f o r e application ......................... Output by manure .................... Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s o n g r a z e d areas . . . . . . . TOTAL

7. 8. 9,

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

. . .

--

SUPPLIES-REMOVALS Changes in a m o u n t o f total soil c o m p o n e n t SUPPLIES:

REMOVALS:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . b y seed f o r s o w i n g . . . . . . . . . . . . . . TOTAL

112 t -10 -41 -163

19. 20. 21. 22. 23. 28. 30.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... O u t p u t by organic m a t t e r , r e m o v e d b~ r u n - o f f . . Transfer by net uptake from soil by plant ..... TOTAL

15 t 1 5 6 -10 126 172

--t

22 25

--15 10 --111 136

-

+12.3

+24

SUPPLIES-REMOVALS

--

9

---30 --0.3 -7 -37.3

3 -t

-65 --4 -91 -160

229

TABLE 77 (continued) System type: Intensive arable

Summary of nutrient flows (units: kg ha-'

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no.Thomas and Gilliam-1

Corn for grain, Northern

Nutrient Changes in amount SUPPLIES:

8a. 9a. 10a.

11. 12. 13a. 14. 15. 16. 17. 26a. 27. REMOVALS:

19. 20. 21. 22. 23. 24. 25. 30t. 30r.

SUPPLIES:

REMOVALS:

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer Transfer Transfer

by application of manure and/or waste . by droppings on grazed areas ....... application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... b y w e a t h e r i n g o f soil m i n e r a l f r a c t i o n . . by mineralization of soil organic fraction by plant production remaining on field . by seed for sowing .............. TOTAL

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... T r a n s f e r b y f i x a t i o n i n soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n Transfer by net uptake by the plant ......... Transfer by net uptake by theplant TOTAL

N

P

Transfer Transfer Input by Input by Transfer Transfer

17. 28.

T r a n s f e r b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n Output by organic matter, removed by run-off.. TOTAL

C h a n g e s in a m o u n t 24. 16.

K

--

---30 ---0.3 --" 7 t -37.3

-112 t --10 50 t -172 15

---

t 15 6 t -(10) 126 -172 0

t 3 t --22 -25 12.3

--65 ---4 pm pm 91 -160 --15 10 t pro_ 111 -136 24

o f soil o r g a n i c m a t t e r

8b. 9b. 10b. 13b. 25. 26b.

by application and/or waste ........ by droppings on grazed areas ....... application of manure ............ application of litter, sludge and waste . b y i m m o b i l i z a t i o n i n soil o r g a n i c f r a c t i o n by plant products remaining on field . . TOTAL

SUPPLIES-REMOVALS

SUPPLY: REMOVAL:

Indiana, U.S.A.

o f a v a i l a b l e soil n u t r i e n t s

SUPPLIES-REMOVALS Changes in amount

y-~ )

--

(--10) 41 51 50 10 60

-----7 7 7 ~ 7

- 9

0

---

pm pm

--------0

o f soil m i n e r a l s T r a n s f e r b y f i x a t i o n i n soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y w e a t h e r i n g o f soil f r a c t i o n . . . . . . . SUPPLY-REMOVAL

pm pm

230

TABLE 78 System type: Intensive arable

Summary of nutrient flows (units: kg ha -I y-i )

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no. Thomas and Gilliam-2

Soybeans for grain, N.E. Arkansas, U.S.A.

Nutrient C h a n g e s in a m o u n t

N

P

K

-120

-37

120

-13 --13

--90 30 -120

--10 3 -13

22 15 -37

0

0

0

of plant component

SUPPLIES:

29. 30t. 30r. 31.

Input by Transfer Transfer Input by

seeds or seedlings ............... b y n e t u p t a k e f r o m soil . . . . . . . . . . . b y n e t u p t a k e f r o m soil . . . . . . . . . . . uptake Irom atmosphere .......... TOTAL

REMOVALS:

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by plant production remaining on field . Transfer by seed for sowing .............. TOTAL SUPPLIES-REMOVALS

C h a n g e s in a m o u n t SUPPLIES:

1.

2. 3. 4. REMOVALS:

5. 6. 7. 8. 9.

37 --

of animal component Input by Input by Transfer Transfer

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

. . .

Output by animal products ............... Output by losses from manure to air, before application ......................... Output by manure .................... Transfer by application of manure and/or waste . Transfer by droppings ongrazed areas ....... TOTAL

--

SUPPLIES-REMOVALS Changes in amount SUPPLIES:

REMOVALS:

o f t o t a l soil c o m p o n e n t

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . by droppings on grazed areas ....... application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . by seed for sowing .............. TOTAL

19. 20. 21. 22. 23. 28. 30.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off.. T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL SUPPLIES-REMOVALS

--123 --10 30 163

---19 ---0.3 3 -22.3

15

---

t 10 3 t 13 120 161 2

t 3 t t 13 16 6.3

--37 ---4 15 56 --15 10 t -37 62 -6

231

T A B L E 78 ( c o n t i n u e d ) System type: Intensive arable

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -~ y - i )

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref. n o . T h o m a s a n d G i l l i a m - 2

Soybeans for grain, N.E. Arkansas, U.S.A.

Nutrient

N

P

K

---19 ---0.3 -3 t -22.3

---

Changes in amount of available soil nutrients SUPPLIES:

REMOVALS:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer Transfer Transfer

19. 20. 21. 22. 23.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Transfer by fixation in soil mineral fraction .... Transfer by i m m o b i l i z a t i o n in soil organic fraction Transfer by net uptake by the plant ......... Transfer by net uptake by the plant ......... TOTAL

24.

25. 30t. 30r.

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by weathering of soil mineral fraction.. by mineralization of soil organic fraction by plant production remaining on field . by seed for sowing .............. TOTAL

--(123) --

-10 -15 t -148 15

---

t 10 3

SUPPLIES-REMOVALS

--15 10 t pm

t

t -. 120 -148

37 ---4 pm -15 -56

.

.

3 t -. 13 -16

0

6.3

. 37 -62 -6

Changes in a m o u n t o f soil organic m a t t e r SUPPLIES:

REMOVALS:

8b. 9b. 10b. 13b. 25. 26b.

Transfer Transfer Input by Input by Transfer Transfer

by application and/or waste ........ b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ application of litter, sludge and waste . by immobilization in soil organic fraction by plant products remaining on field . . TOTAL

17. 28.

Transfer by mineralization of soil organic fraction Output by organic matter, removed by run-off . . TOTAL

--

-----3 3

30 30 15 13 28

SUPPLIES-REMOVALS

2

3

---t --

3

----

0

0

pm pm

pm pm

t

Changes in a m o u n t o f soil minerals SUPPLY: REMOVAL:

24. 16.

Transfer by f i x a t i o n in soil m i n e r a l fraction . . . . Transfer by weathering of soil fraction ....... SUPPLY-REMOVAL

--

232

T A B L E 79 System type: Intensive arable

Summary of n u t r i e n t flows ( u n i t s : kg ha - I y - i )

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref. n o . T h o m a s a n d G i l l i a m - 3

Wheat, Central Kansas, U.S.A.

Nutrient

N

P

K

-56 --56

-10 --10

-50 --50

--36 20 -56

--7 3 -10

---

0

0

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

29. 30t. 30r. 31.

Input by Transfer Transfer Input by

seeds or seedlings ............... by net uptake from soil ........... by net uptake from soil ........... uptake from atmosphere .......... TOTAL

REMOVALS:

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by plant production remaining on field . Transfer by seed for sowing .............. TOTAL SUPPLIES-REMOVALS

6 44 -50 0

Changes in a m o u n t of animal c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4.

Input by Input by Transfer Transfer

5. 6.

Output by animal products ............... O u t p u t b y l o s s e s f r o m m a n u r e t o air, b e f o r e application ......................... Output by manure .................... Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s o n g r a z e d areas . . . . . . . TOTAL

7. 8. 9.

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

. . .

--

SUPPLIES-REMOVALS C h a n g e s in a m o u n t o f t o t a l s o i l c o m p o n e n t SUPPLIES:

REMOVALS:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers . . : ................. N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . by seed for sowing .............. TOTAL

19. 20. 21. 22. 23. 28. 30.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off . . Transfer by net uptake from soil by plant ..... TOTAL SUPPLIES-REMOVALS

---34 t -6 20 -60 5 t 4 1 t 4 56 70 -10

---13 ---0.1 3 -16.1 --t 3 t t 10 13 +3.1

--0 --2 44 -46 --5 5 t -50 60 -14

233

T A B L E 79 ( c o n t i n u e d ) System type: Intensive arable

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -1 y - i )

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref. n o . T h o m a s a n d G i l l i a m - 3

Wheat, Central Kansas, U.S.A.

Nutrient

N

P

K

--

---13 ---0.1 -3 t -16.1

Changes in a m o u n t o f available soil n u t r i e n t s SUPPLIES:

REMOVALS:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer Transfer Transfer

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by weathering of soil mineral fraction.. by mineralization of soil organic fraction by plant production remaining on field . by seed for sowing .............. TOTAL

19. 20. 21. 22. 23. 24. 25. 30t. 30r.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Transfer by f i x a t i o n in soil m i n e r a l fraction . . . . Transfer by immobilization in soil organic fraction Transfer by net uptake by the plant ......... Transfer by net uptake by the plant ......... TOTAL SUPPLIES-REMOVALS

34 t --

6 -28 t -68 5

---

-

0 --2 pm -44 -46

3

--5 5

--10 -13

t pm -50 -60

t 4 1 t -( 4) 56 -70

--

t t

2

3.1

-14

Changes in a m o u n t o f soil organic m a t t e r SUPPLIES:

8b. 9b. 10b. 13b. 25.

26b. REMOVALS:

17. 28.

Transfer Transfer Input by Input by Transfer Transfer

by application and/or waste ........ by d r o p p i n g s on grazed areas . . . . . . . application of manure ............ application of litter, sludge and waste . by immobilization in soil organic fraction by plant products remaining on field . . TOTAL

--

-( 4 )

28 4 32 -

8

Changes in amount of soil minerals SUPPLY: REMOVAL:

24. 16.

Transfer by fixation in soil mineral fraction .... T r a n s f e r b y w e a t h e r i n g o f s o i l f r a c t i o n . . .~ . . . . SUPPLY-REMOVAL

--

20 24

Transfer by mineralization of soil organic fraction Output by organic matter, removed by run-off . . TOTAL SUPPLIES-REMOVALS

----

--

---

3 3 3

----t 0

3

--0

0

0

t

234

TABLE 80 System type: Intensive arable

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -~ y - I )

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref. n o . T h o m a s a n d G i l l i a m - 4

Irish p o t a t o e s , Maine, U.S.A.

N

Nutrient

P

K

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

REMOVALS:

29. 30t. 30r. 31.

Input by Transfer Transfer Input by

seeds or seedlings ............... by net uptake from soil ........... by net uptake from soil ........... uptake from atmosphere .......... TOTAL

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by plant production remaining on field . Transfer by seed for sowing .............. TOTAL

1-45 --145

-16 --16

177 --177

--80 65 -145

--10 6 -16

--117 60 -177

0

0

0

SUPPLIES-REMOVALS Changes in a m o u n t o f animal c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4.

Input by Input by Transfer Transfer

5. 6.

Output by animal products ............... O u t p u t b y losses f r o m m a n u r e t o air, b e f o r e application ......................... Output by manure .................... Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s o n g r a z e d areas . . . . . . . TOTAL

7. 8. 9.

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

. . .

--

SUPPLIES-REMOVALS Changes in a m o u n t o f t o t a l soil c o m p o n e n t SUPPLIES :

REMOVALS:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27. 19. 20. 21. 22. 23. 28. 30.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . b y Seed f o r s o w i n g . . . . . . . . . . . . . . TOTAL

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off . . Transfer by net uptake from soil by plant ..... TOTAL SUPPLIES-REMOVALS

---168 t -6 65 -2-39

---101 ---0.1 6

---207 ---

107.1

270

---

--20 15

15 t 64 5

t

t 10 145 239

t t

0

3 60

5 t 16 21

-177 212

86

58

235

TABLE 80 (continued} System type: Intensive arable

Summary of n u t r i e n t flows ( u n i t s : kg h a - '

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref. n o . T h o m a s a n d G i l l i a m - 4

Irish p o t a t o e s , Maine, U.S.A.

Nutrient

N

y-' )

P

K

---101 ---0.1 -6 --107.1

--

Changes in a m o u n t o f available soil n u t r i e n t s SUPPLIES:

REMOVALS:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer Transfer Transfer

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by weathering of soil mineral fraction.. by mineralization of soil organic fraction by plant production remaining on field . by seed for sowing .............. TOTAL

19. 20. 21. 22. 23. 24. 25. 30t. 30r.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Transfer by fixation in soil mineral fraction . . .. Transfer by i m m o b i l i z a t i o n in soil organic fraction Transfer by net uptake by the plant ......... Transfer by net uptake by the plant ......... TOTAL

--168 t ---6 -65 --239 15

---

t 64 5

t

t -(10) 145 -239

t

SUPPLIES-REMOVALS

0

-207 --3 pm -60 -270

5

--20 15

--16 -21

t pm -177 -212

86

58

Changes in a m o u n t o f soil organic m a t t e r SUPPLIES:

REMOVALS:

8b. 9b. 10b. 13b. 25. 26b.

Transfer Transfer Input by Input by Transfer Transfer

by application and/or waste ........ b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ application of litter, sludge and waste . by immobilization in soil organic fraction by plant products remaining on field . . TOTAL

17. 28.

Transfer by mineralization of soil organic fraction Output by organic matter, removed by run-off.. TOTAL

---(10) 65 75 65 10 75

SUPPLIES-REMOVALS

0

Changes in a m o u n t o f soil minerals SUPPLY: REMOVAL:

24. 16.

Transfer by fixation in soil mineral fraction .... Transfer by weathering of soil fraction ....... SUPPLY-REMOVAL

---

------

---

6 6

-----

6 6

----

--

0

0

236

T A B L E 81 System type: Intensive arable

Summary of n u t r i e n t flows (units: kg ha -I y-1 )

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref. n o . T h o m a s a n d O i l l i a m - 5

Cotton, California, U.S.A.

Nutrient

N

P

K

-127 --

-19 --19

-67 -67

79 48 -127

--13 6 -19

30 37 -67

0

0

0

Changes in amount of plant component SUPPLIES:

REMOVALS:

29. 30t. 30r. 31. 3. 4. 18. 26. 27.

Input by Transfer Transfer Input by

seeds or seedlings ............... by net uptake from soil ........... by net uptake from soil ........... uptake from atmosphere .......... TOTAL

127

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by plant production remaining on field . Transfer by seed for sowing .............. TOTAL

--

SUPPLIES-REMOVALS

--

Changes in amount of animal component SUPPLIES:

1.

2. 3. 4. REMOVALS:

5. 6. 7. 8. 9.

Input by Input by Transfer Transfer

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

. . .

Output by animal products ............... O u t p u t b y l o s s e s f r o m m a n u r e t o air, b e f o r e application ......................... Output by manure .................... Transfer by application of manure and/or waste . Transfer b y d r o p p i n g s o n g r a z e d areas . . . . . . . TOTAL

--

SUPPLIES-REMOVALS Changes in a m o u n t o f total soil c o m p o n e n t SUPPLIES:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . by seed for sowing .............. TOTAL

REMOVALS:

19. 20. 21. 22. 23. 28. 30.

Output by denitrification ........ ; ....... Output by volatilization of ammonia . ....... Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off . . Transfer by net uptake from soil by plant ..... TOTAL SUPPLIES-REMOVALS

---179 t -50 3 48 -280

---14 --t t 6 -20

---0 --50 1 37 -88

20

---

83 50 t t 127 280

t 1 t t 19 20

--10 10 t -67 87

0

0

+1

t

237

TABLE 81 (continued) System type: Intensive arable

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -~ y - ~ )

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no. Thomas and Gilliam-5

Cotton, California, U.S.A.

Nutrient C h a n g e s in a m o u n t SUPPLIES:

REMOVALS:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer Transfer Transfer

19. 20. 21. 22. 23. 24. 25. 30t.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Transfer by fixation in soil mineral fraction .... T r a n s f e r b y i m m o b i l i z a t i o n in s o i l o r g a n i c f r a c t i o n Transfer by net uptake by the plant ......... Transfer by net uptake by the plant TOTAL

30r.

N

P

K

---

---14 --t t -6 t

---

-50 1 pm -37

20

88

---

o f a v a i l a b l e soil n u t r i e n t s by application of manure and/or waste . by droppings on grazed areas ....... application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . im'gation and flooding ........... dry and wet deposition ........... by weathering of soil mineral fraction.. by mineralization of soil organic fraction by plant production remaining on field . b y s e e d f o r sowingTOTAL ..............

179 t -50 3 -48 t 28--0 20

t

t

--127 -280

--19 -20

--10 10 t --67 -87

0

0

+1

--

--48 48

-----6 6 6

---

t 83 50

SUPPLIES-REMOVALS C h a n g e s in a m o u n t SUPPLIES:

REMOVALS:

Transfer Transfer Input by Input by Transfer Transfer

by application and/or waste ........ by droppings on grazed areas ....... application of manure ............ application of litter, sludge and waste . b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n by plant products remaining on field . . TOTAL

17. 28.

Transfer by mineralization of soil organic fraction Output by organic matter, removed by run-off., TOTAL

24. 16.

1

--

48 t

t

---

48

6

0

0

--

---

--

SUPPLIES-REMOVALS

SUPPLY: REMOVAL:

t

o f soil o r g a n i c m a t t e r

8b. 9b. 10b. 13b. 25. 26b.

Changes in amount

0

of soil minerals Transfer by fixation in soil mineral fraction .... Transfer by weathering of soil fraction ~. ..... SUPPLY-REMOVAL

--

238

TABLE 82 System type: Intensive livestock

Summary of nutrient flows (units: kg ha -I y-I )

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref. n o . T h o m a s a n d G i l l i a m - 6

Grazed bluegrass, Western North Carolina, U.S.A.

Nutrient

N

P

K

-151 --151

-20 --20

-150 --150

-151 --

-150 ---

151

-20 ---20

150

0

0

0

-150 150 23

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

29. 30t.

30r. 31. REMOVALS:

3.

4. 18. 26. 27.

Input by Transfer Transfer Input by

seeds or seedlings . . . . . . . . . . . . . . . b y n e t u p t a k e f r o m soil . . . . . . . . . . . by net uptake from soil ........... uptake from atmosphere .......... TOTAL

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by plant production remaining on field . Transfer by seed for sowing .............. TOTAL SUPPLIES-REMOVALS

Changes in a m o u n t o f animal c o m p o n e n t SUPPLIES :

REMOVALS:

1. 2. 3. 4.

Input by Input by Transfer Transfer

. . .

-151 151

---20 20

5. 6.

Output by animal products ............... Out~. u t b y l o s s e s f r o m m a n u r e t o air, b e f o r e application ......................... Output by manure .................... Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s o n g r a z e d areas . . . . . . . TOTAL

38

5

7. 8. 9.

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

--

SUPPLIES-REMOVALS

--

--

~3 151

---15 20

--127 150

0

0

0

Changes in a m o u n t o f t o t a l soil c o m p o n e n t SUPPLIES:

REMOVALS:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . by seed for sowing .............. TOTAL

-113 -168 pm --

19. 20. 21. 22. 23. 28. 30.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off . . Transfer by net uptake from soil by plant ..... TOTAL SUPPLIES-REMOVALS

-127 -46 ---

291

-15 -24 ---0.3 --39.3

5 98 -t 12

---0.2

----

2 151 268

t t 20 20.2

+23

+19.1

10 --

4 -177

6 t 150 156 +21

239

TABLE 82 (continued) System type: Intensive livestock

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -1 y - i )

T y p e o f farm or e c o s y s t e m or t y p e o f part o f a f a r m o r e c o s y s t e m , ref. n o . T h o m a s a n d G i l l i a m - 6

Grazed bluegrass, Western North Carolina, U.S.A.

Nutrient

N

P

K

C h a n g e s in a m o u n t o f a v a i l a b l e s o i l n u t r i e n t s SUPPLIES:

REMOVALS:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer Transfer Transfer

19. 20.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Transfer by f i x a t i o n in soil m i n e r a l fraction . . . . Transfer by immobilization in soil organic fraction Transfer by net uptake by the plant ......... Transfer by net uptake by the plant TOTAL

21.

22. 23. 24. 25. 30t. 30r.

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irn'gation and floodlng ........... dry and wet deposition ........... by weathering of soil mineral fraction.. by mineralization of soil organic fraction by plant production remaining on field . b y s e e d f o r s o w i n~ g . . . . . . . . . . . . . . TOTAL

-53 -168 pm --

-10 -24 ---0.3 -5 --39.3

10 48 -279 5 (98) -12 t -(13) 151 -279

SUPPLIES-REMOVALS

0

-127 -46 --4 pm ---177

--

--

--

--

--

--

0.2 t --20 -20.2

6 t pm -150 -156

+19

+21

--

--------

Changes in a m o u n t o f soil organic m a t t e r SUPPLIES:

REMOVALS:

8b. 9b. lOb. 13b. 25. 26b.

Transfer Transfer Input by Input by Transfer Transfer

by application and/or waste ........ by d r o p p i n g s on grazed areas . . . . . . . application of manure ............ application of litter, sludge and waste . by i m m o b i l i z a t i o n in soil organic fraction by plant products remaining on field . . TOTAL

17. 28.

Transfer by mineralization of soil organic fraction Output by organic matter, removed by run-off.. TOTAL SUPPLIES-REMOVALS

-60 --(13) -73 48 2 50 +23

Changes in a m o u n t o f soil minerals SUPPLY: REMOVAL:

24. 16.

Transfer by f i x a t i o n in soil m i n e r a l fracti'on . . . . Transfer by weathering of soil fraction ....... SUPPLY-REMOVAL

---

5 ----5 5 t 5 0

---0

240

T A B L E 83 System type: Extensive forestry

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -~ y - ~ )

J

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref. n o . T h o m a s a n d G i l l i a m - 7

Loblolly pine, 40 years, Mississippi, U.S.A.

Nutrient

N

P

K

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

REMOVALS:

29. 30t. 30r. 31.

Input by Transfer Transfer Input by

seeds or seedlings ............... by net uptake from soil ........... b y n e t u p t a k e f r o m soil . . . . . . . . . . . u p t a k e f r o m atTmOo~ph~re . . . . . . . . . .

-20.4

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer b y p l a n t p r o d u c t i o n r e m a i n i n g on field . Transfer by seed for sowing .............. TOTAL

2-0.4

-1.5 -1.5

--11.6 8.8 -20.4

--0.7 0.8 -1.5

SUPPLIES-REMOVALS

0

0

-9.4 9.4 -7.3 2.1 -9.4 0

Changes in a m o u n t o f animal c o m p o n e n t SUPPLIES:

1.

2. 3. 4. REMOVALS:

5. 6. 7. 8.

9.

Input by Input by Transfer Transfer

feed f o r l i v e s t o c k . . . . . . . . . . . . . . . litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

. . .

Output by animal products ............... O u t p u t b y l o s s e s f r o m m a n u r e t o air, b e f o r e application ......................... Output by manure .................... Transfer by application of manure and/or w~te T r a n s f e r b y d r o p p i n g s o n g r a z e d areas . . . . . . . TOTAL

-.

SUPPLIES-REMOVALS C h a n g e s in a m o u n t o f t o t a l s o i l c o m p o n e n t SUPPLIES:

REMOVALS:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . by seed for sowing .............. TOTAL

19. 20. 21. 22. 23. 28. 30.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off . . Transfer by net uptake from soil by plant ..... TOTAL SUPPLIES-REMOVALS

--

-------0.3 0.8 -1.1

-(8) --11 8.8 -27.8 1

---

----4 2.1 -6.1

-1.5 1.6

--2 3 t -9.4 14.4

-0.5

-8.3

t 1 3

t

t -20.4 25.4

t

2.4

--

1

241

TABLE 83 (continued) System type: Extensive forestry

Summary of nutrient flows (units: kg ha-'

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref. n o . T h o m a s a n d G i l l i a m - 7

y-' )

L o b l o l l y pine, 40 years, Mississippi, U.S.A.

Nutrient

N

P

K

----(8) --

-------0,3 -pm --0.3

Changes in a m o u n t o f available soil n u t r i e n t s SUPPLIES:

REMOVALS:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer Transfer Transfer

19. 20. 21. 22. 23. 24. 25. 30t.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Transfer by f i x a t i o n in soil m i n e r a l fraction . . . . Transfer by i m m o b i l i z a t i o n in soil organic fraction Transfer by net uptake by the plant ......... Transfer by net uptake by the plant ......... TOTAL

30r.

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by weathering of soil mineral fraction.. by mineralization of soil organic fraction by plant production remaining on field . b y s e e d f o r s o w i na g . . . . . . . . . . . . . . TOTAL

SUPPLIES-REMOVALS

11 -6 --25 1

4 --2.1 -6.1

---

t 1 3

-------

--2 3

t

t -pm 20.4 -25.4

1 t -pm 1.5 -2.5

--9.4 -14.4

-0.4

-1.3

-8.3

t

Changes in amount of soil organic matter SUPPLIES:

REMOVALS:

8b. 9b. 10b. 13b. 25. 26b.

Transfer Transfer Input by Input by Transfer Transfer

by application and/or waste ........ b y d r o p p i n g s on grazed areas . . . . . . . application of manure ............ application of litter, sludge and waste . by i m m o b i l i z a t i o n in soil organic fraction by plant produe~s remaining on field . . TOTAL

17. 28.

Transfer by mineralization of soil organic fraction Output by organic matter, removed by run-off . . TOTAL SUPPLIES-REMOVALS

-

8.8 8.8 6 -6 +2.8

Changes in amount of soil minerals SUPPLY: REMOVAL:

24. 16.

Transfer by f i x a t i o n in soil m i n e r a l fraction . . . . Transfer by weathering of soil fraction ........ SUPPLY-REMOVAL

---

----0.8 0.8 pm 0 +0.8

-----

242

TABLE 84 System type: Extensive forestry

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a - l y-~ )

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref. n o . T h o m a s a n d G i l l i a m - 8

D o u g l a s fir, 3 7 y e a r s , W a s h i n g t o n , U . S . A .

Nutrient

N

P

K

C h a n g e s in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

REMOVALS:

29. 30t. 30r. 31.

Input by Transfer Transfer Input by

seeds or seedlings ............... by net uptake from soil ........... by net uptake from soil ........... uptake from atmosphere .......... TOTAL

-35.1 --

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by plant production remaining on field . Transfer by seed for sowing .............. TOTAL

35.1

-6.2 --6.2

14.4

--10.3 24.8 -35.1

--1.7 4.5 -6.2

--10.5 3.9 -14.4

SUPPLIES-REMOVALS

0

0

14.4 --

0

Changes in a m o u n t of animal c o m p o n e n t SUPPLIES:

1. 2.

3. 4. REMOVALS:

5. 6. 7. 8. 9."

Input by Input by Transfer Transfer

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

. . .

Output by animal products ............... O u t p u t b y losses f r o m m a n u r e t o air, b e f o r e application ......................... Output by manure .................... Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s o n g r a z e d areas . . . . . . . TOTAL

--

SUPPLIES-REMOVALS Changes in a m o u n t of t o t a l soil c o m p o n e n t SUPPLIES:

REMOVALS:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . by seed for sowing .............. TOTAL

19. 20. 21. 22. 23. 28. 30.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off . . T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL SUPPLIES-REMOVALS

---

-------0.3 4.5 -4.8

----4 3.9 -7.9

1 35.1 39.1

----t t 6.2 6.2

--1 1 t -14.4 16.4

-4.3

-1.4

-8.5

-pm --

-10 24.8 -34.8 1 t 1 1 t

---

243

TABLE 84 (continued) System type: Extensive forestry

Summary of nutrient flows (units: kg ha -I y-i )

T y p e o f farm or e c o s y s t e m or t y p e o f part o f a f a r m o r e c o s y s t e m , ref. n o . T h o m a s a n d G i l l i a m - 8

D o u g l a s fir, 37 years, W a s h i n g t o n , U . S . A .

Nutrient

N

P

K

Changes in a m o u n t o f available soil n u t r i e n t s SUPPLIES:

REMOVALS:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer Transfer Transfer

by application of manure and/or waste . by d r o p p i n g s on grazed areas . . . . . . . application of manure ............ fertilizers .................... N-fixation application of litter, sludge and waste . irrigation and fiood~ng ........... dry and wet deposition ........... by weathering of soil mineral fraction . . by mineralization of soil organic fraction by plant production remaining on field . by seed for sowing .............. TOTAL

19. 20. 21. 22. 23. 24. 25. 30t. 30r.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Transfer by f i x a t i o n in soil m i n e r a l fraction . . . . Transfer by immobilization in soil organic fraction Transfer by net uptake by the plant ......... Transfer by net uptake by the plant . . . . . TOTAL SUPPLIES-REMOVALS

---

-------0.3 ----0.3

-pm -10 -pm --10 1

---4 pm -39 -7.9

--t t t --6.2 . . . 6.2

t 1 1 t --35.1 . . 38.1

---

.

-28.1

--1 1 t --14.4 . 16.4

-5.9

-

8.5

Changes in a m o u n t o f soil organic m a t t e r SUPPLIES:

REMOVALS:

8b. 9b. 10b. 13b. 25. 26b.

Transfer Transfer Input by Input by Transfer Transfer

by application and/or waste ........ -b y d r o p p i n g s o n g r a z e d areas . . . . . application of manure ............ -application of litter, sludge and waste . -by i m m o b i l i z a t i o n in soil organic fraction -by plant products remaining on field . . 24.8 TOTAL 24.8

17. 28.

Transfer by mineralization of soil organic fraction Output by organic matter, removed by run-off.. TOTAL SUPPLIES-REMOVALS

-1.0 1.0 23.8

Changes in amount of soil minerals

SUPPLY: REMOVAL:

24. 16.

Transfer by f i x a t i o n in soil m i n e r a l fraction . . . . Transfer by weathering of soil fraction SUPPLY-REMOVAL

--

.

.

-. . ---4.5 4.5 ---4.5

-. ----------

244 6.11. AGRO-ECOSYSTEMS IN SOUTH AMERICA (G.St. Husz)

6.11.1. Introduction

Both the extensiveness of the area and the lack of data at present do n o t allow a very accurate description of all agro-ecosystems existing in the continent of South America. Only 5% of the total area of Latin America is used for crop production, whilst 18% is used as extremely extensive pastures (Walter and Lieth, 1960; Cole, 1965; Ganssen and Hadrich, 1965; Schmithausen, 1968; Duckham and Masefield, 1970; Husz, 1973, 1974; De Geus, 1973). Technical and economic difficulties and the lack of an adequate infrastructure prevent the introduction of fertilizers and herbicides. Climatic waterbalances and soil moisture conditions are usually unfavorable for agricultural purposes. The rural population contributes a smaller a m o u n t to the gross national product (GNP), as ought to be expected by their numerical representation. At the same time, the capital investments in the rural region are relatively lower than its share of the gross domestic p r o d u c t . The need to increase agricultural production usually has not resulted in higher productivity but merely in the extension of arable land maintained by poor agricultural techniques. Consequently per capita productivity has remained low as shown by the following relative figures for South American and other countries: France Canada U.S.A.

100 150 216

Guatemala Venezuela

16 24

Argentina Columbia

69 34

Nevertheless, improved agricultural technology and increased productivity have been reported from many regions during the last 10--20 years. 6.11.2. Methods

The lack of certain kinds of data requires a special approach for calculating nutrient balances. The idea is to use a simple model which can be applied all over the continent and to obtain comparable figures. This model should allow the primary productivity of ecosystems to be estimated and the nutrient balances to be calculated on the basis of nutrient contents and environmental situations, especially climatic and soil conditions. We started from the equation: 10 ET a yield = - - Qs" Qv KT

245

where the yield is expressed in t ha-' and year, above ground dry matter, ETa = actual evapotranspiration (mm y - ' , being determined as the sum of monthly values, which have to be determined considering the actual water balances of each month), KT = m 3 of water transpired by the plant per t dry matter produced, Qs = soil quality index, Qv = shoot index. The amounts of nutrients absorbed are then calculated by multiplication, taking into consideration the average N, P and K content of the vegetation. The actual evapotranspiration is calculated from the observations of 280 weather stations. As long as water is available, the actual evapotranspiration equals the potential evaporation; thereafter the actual amount of available soil water is taken into account. The potential evapotranspiration, ETp (mm d a y - ' ), is calculated from data of 48 stations and equals: E T p = 0.1557 × T '''s69 where T is the m e a n monthly temperature (r2 = 0.946, F 1.46 = 813.2). The data points are s h o w n in Fig. 36. The shoot index is a function of precipitation surplus or deficit.It ranges from 0.4 for a deficit of 1000 m m per year, via 0.5 for equilibrium, to 0.6 for a surplus of 1000 m m per year.

S h o o t index (Qv) = 0.5 + 10 -4 • (Ny -- ETpy) where Ny = annual precipitation and ETpy = annual potential evapotranspiration. Shoot index is the quotient of above ground dry matter and total primary dry mass produced. b ~7

•

W "

y = 01557246 r 2 : 09465 r : 09729 F~4e: 813.19 n = 48

6 5

X

1156932

•

• • / •~.~o

•

• o ~o

,o ~ / . o exe

4

x

x

3

•

Xo

•

•

.

1

2

3

4

5

6

7

8

9

10 11

1; 1~1 115 16 117 18 lCj 20 21 22 213:24 × : t°C (~Mo)

Fig. 36. The potential evapotranspiration ETp (mm d a y - ' ) as a function of the temperature

246

0~ ~

~

08

,

0.6

/

J

/

85,10-4÷162.1£~4.x _.63.1d6x2

~

~

36.9 10-4 + 142.10-4. x _ 576.10-6. ×2

/

y= :36'910-4+11610-4-x-46 9 ' 10-6' x 2

05

.

0

.

.

.

.

10 20 30 40 50 60 70 80 90 100

V [°/o]

Fig. 37. The soil quality index Qs as a function of the soil texture and of the cation ex. change capacity (CEC) saturation degree.

Fig. 38. Soil quality indices.

247

T h e soil q u a l i t y index, Qs, is derived (Husz, 1 9 7 6 ) f r o m p r o d u c t i v i t y data. T h e c a t i o n e x c h a n g e c a p a c i t y s a t u r a t i o n degree is t h e m a i n variable, s e p a r a t e f u n c t i o n s b e i n g derived f o r sand, clay, s a n d y l o a m a n d l o a m . T h e e q u a t i o n s are: soil soil soil soil

quality quality quality quality

index index index index

(sand) (sandy loam) (loam) (clay)

= = = =

0.0051 0.0037 0.0085 0.0036

+ + + +

0.0079 0.0142 0.0162 0.0116

x x x x

-

0.000040 0.000058 0.000063 0.000047

x2 x2 x: x2

w h e r e x is t h e degree o f c a t i o n s a t u r a t i o n in %. T h e curves o b t a i n e d are s h o w n in Fig. 37. A m a p o f t h e soil q u a l i t y indices is p r e s e n t e d in Fig. 38.

6.11.3. Description of the systems N i n e a g r o - e c o s y s t e m s are c o n s i d e r e d , t w o o f w h i c h are split i n t o an arable p a r t a n d a l i v e s t o c k p a r t giving in t o t a l 12 balances calculated. T h e areas to w h i c h t h e s y s t e m s a p p l y are s h o w n in Fig. 39.

Fig. 39. Geographical distribution o f various e c o s y s t e m s . T h e numbers indicate the reference numbers.

248

6.11.3.1. Steppe and semi-desert of Patagonia Classification. Extensive livestock. Reference: Husz-1; Steppe and semi-desert of Patagonia, Table 86.

Location: East of ~he Andes, southeast of a line through 38 ° S and 71 ° W in the direction of the Gulf of San Jorge. This zone can be subdivided into three parts: the central region, the northwestern region (Sub-Andes) and southern Tierra del Fuego.

Central region Location: East of the Andes, between 38 ° and 47 ° SL; altitude, 0--1500 m. Climate and water regime: Mean annual temperature, 8--14°C; mean annual temperature amplitude, 13°C; annual precipitation, 10--20 cm. (The mean values for the three regions are: precipitation, 30.6 cm; potential evapotranspiration, 76.4 cm; actual evapotranspiration, 23.9 cm.) Soil: Plains with terraces and wide valleys. Soils not well developed as a result of dryness. In the north, aeolian sediments; near the Andes,Lithosols, partly as sandy Rhegosols, partly as calcareous Yermosols (without Argillic B horizon). In the valleys, development of saline softs (solontchaks and solonetz). In the south, tertiary marine sediments, also quarternary fluviatile and aeolian sediments. The older soils consist of reddish Yermosols with calcareous and saline horizons. Valleys are more fertile and productive than other areas (mean value for the three regions: productivity index Qs = 0.586, after improvement of the soil Qs = 0.9). Vegetation: Grass and shrub steppes: Chuquiraga avellanedae, Nassauvia

glomerulosa, Stipa humilis, Prosopis patagonica, Lycium ameghinoi, Berberis cuneata, Verbena ligustrina, Pleurophora patagonica, Haplopappus diplopappus, Grindelia chiloensis, Euphorbia portulacoides. Halophytes: Atriplex lampa, A. sagittifolia, Frankenia patagonica, L ycium ameghinoi, Prosopis patagonica. Shoot index: 0.454. Use: For all three regions, sheep.

Productivity and nutrient balance: Mean values for the three regions: calculated total dry matter production, 4672 kg ha-l; shoots, 2121 kg ha-l; roots, 2551 kg ha -1. Mean nutrient values for this t y p e of steppe vegetation (above ground): N, 0.011 kg kg -~ dry matter; P, 0.0018 kg kg -1 dry matter; K, 0.010 kg kg -1 dry matter. Although a dry matter production of 2121 kg ha -1 in well managed areas allows 5--6 sheep ha -~, the density is limited to less than 1 sheep ha -~ in this steppe due to the low nutrient content of the vegetation and the dry periods. Compared to Europe, the amount of nutrients in the excrements (urine + faeces) is low, expressed as kg per sheep per year:

N P K

Europe

Patagonia

15.0 2.5 8.9

7.9 3.8 7.2

249

Where the soil has been improved (Qs = 0.9), the production (above ground) increases to 3227 kg dry matter ha- ~ (Roemer and Scheffer, 1953; Schiller et al., 1967; De Geus, 1973; Ruhrstickstoff, 1974).

North-western region Data applicable to all three regions, see Central region. Location: Near the Andes between 38 ° and 47 ° SL. Altitude, 200--600 m. Climate: Mean annual temperature, 8--13°C; mean annual temperature amplitude, 13°C; mean precipitation, 2 0 - 6 0 cm. Soil: Intermediate region between steppes and semi-desert of central plain and grass and shrub vegetation of the Andes. Hilly landscape, soil types: Cambisols, Andosols, Rhegosols and Lithosols. Vegetation: Grass and shrub steppes: Mulinum spinosum, Nassauvia glomerulosa, N. aculeata, Berberis cuneata, Adesmia, Senecio filaginoides, Lycium tenuispinossum, Stipa patagonica, S. humilis, S. chrysophylla, Festuca monticola, Agrostis pyrogea, Deschampsia elegantula, Poa ligularis, Bromus macranthus, Danthonia. For most pastures: Juncus lesueurii, Carex gayana, C. nebularum, Acaena macrostemon. Use: Sheep. Southern Tierra del Fuego Data applicable to all three regions, see Central region. Location: South of 51 ° SL, the so-called Patagonian prairie. Altitude, 0--500 m. Climate: Mean annual temperature, 5--7°C; mean annual temperature amplitude, 5--9 C; mean annual precipitation, 20--50 cm. Soil: Tertiary marine sediment, also Pleistocene material. Well developed A-horizon, rich in undecomposed or partly decomposed organic matter and root material, partly ranker soils; in valleys also black A/C soils, comparable to Para-Rendzinas. Vegetation: Grass and shrub steppes: Mulinum spinosum, Nassauvia aculeata, Berberis cuneata, Festuca gracillima, Hordeum comosum, Poa ligularis, Agropyron magellanicum, Senecio patagonicus, Azorella.

0.0 (Import)

~;

( Export )

O0 060

23.

_

~_

[73 t

....

]T!~_c~ _

SOIL

Fig. 40. Nitrogen flow chart, grazed Patagonian steppe, system Husz-1, kg N h a - ' .

22.72

Total

N-balance

trace

7.32

15.40

Waste Fertilizers Uptake by vegetation Grazed Excrements Sold Private consumption

0.60

23.33

23.33

23.33

23.33

In

In

Out

Plant

Soil

23.32

7.92

15.40

Out

0

7.92

7.92

In

Animals

0

7.92

7.32 0.60 trace

Out

trace

In

Human

0

trace

Out

Simplified nitrogen balance, Patagonian steppe, system Husz-1 (above ground d w matter only)

TABLE 85

0

Import

0.60

0.60

0.60

Export

fj1 Q

251

Use: Sheep. Productivity and nutrient balance: Fig. 40 shows a simplified nutrient flow chart for this area; Table 85 shows the corresponding nutrient balance for nitrogen. (In a first draft of Husz' manuscript all areas were analyzed in this way, b u t because of the large amount of space required by such balances they are replaced by the usual nutrient flow tables in the final version.)

6.11.3.2. Argentinian shrub steppe (Monte) Classification. Extensive arable. Reference: Husz-2; Shrub steppe (Monte), Argentina, Table 87.

Location: Mid-Argentina, from the spurs of the Andes (northwestern part of the area) to the Gulf of St. Mathias on the Atlantic ocean (southeastern part). Altitude ranges from 0 to 1000 m. Climate: Mean annual temperature: 14--20°C; mean annual temperature range: 16°C; annual precipitation: 10--35 cm; mean value: 31.3 cm; potential evapotranspiration: 147.6 cm; actual evapotranspiration: 31.3 cm. Soil: The flattest and slightly hilly areas have soils of different age on loose sediments of a mainly sandy nature. The main soil formation can be described as " K a s t a n o z e m " (without Argillic B-horizon). It is associated with Rhegosols. These soil types are mostly calcareous. Moving southward, the humus percentage decreases. In this area, more Xerosols can be found. In the valleys, Fluvisols accompanied by Solonetz and gleyish Solonchaks occur. Productivity index, Qs = 0.69. Vegetation: Main vegetation types with characteristic shrub species: shrub steppe (Larrea divaricata, L. cuneifolia, L. nitida, Bougainvillea spinosa, Prosopis alpataco, P. strombulifera, P. globosa, Cassia aphylla, Atamisquea emarginata, Condalia microphylla, Cercidium australe, Tricomaria usillo, Monttea aphylla, Chuquiraga crinacea). Halophyte vegetation (Suaeda divaricata, A triplex lampa, A. sagittifolia, Cyclolepis genistoides, Frankenia patagonica, Salicornia ambigua, Heterostachys, Allenrolfia patagonica). Shoot index = 0.384. Use: Arable farming is impossible in the Monte without irrigation. With irrigation it is possible to cultivate wheat, corn, tobacco, vegetables and tomatoes, while special crops like grapevines can also be grown. The nutrient balance and system description refer to the non-irrigated areas. Productivity and nutrient balance: The composition of the vegetation on the extensive pastures is rather heterogeneous because of local salinity problems. The total dry matter productivity is 4095 kg ha -1 annually, b u t of the mean 2784 kg above-ground vegetation, only 30% or 835 kg can be used to feed cattle. This allows for a live weight of 116 kg cattle per ha. Phosphate is the factor limiting production. The animals have to consume 27 kg dry matter per kg live weight per year to meet their P requirements, that is, a b o u t three times as much as on well managed pastures. The potential above ground pro-

252

TABLE 86 System type: Extensive livestock

Summary of n u t r i e n t flows (units: kg h a - '

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref. n o . Husz-1

y-~ )

Steppe and semi-desert, Patagonia

Nutrient

N

P

K

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

29. 30t. 30r. 31.

Input by Transfer Transfer Input by

seeds or seedlings . . . . . . . . . . . . . . . b y n e t u p t a k e f r o m soil . . . . . . . . . . . by net uptake from soil ........... uptake from atmosphere .......... TOTAL

-23.3 20.4 t 43.7

REMOVALS:

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by p l a n t p r o d u c t i o n r e m a i n i n g on field . Transfer by seed for sowing .............. TOTAL SUPPLIES-REMOVALS

7.9 3-5.8 -43.7

-3.8 5.1 0 8.9

-21.2 25.5 0 46.7

-1.3 -7.6 -8.9

--

0

0

---7.9 7.9

----

7.2 39.5 -46.7 0

Changes in a m o u n t o f animal c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4. 5. 6.

7. 8. 9.

Input by Input by Transfer Transfer

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

. . .

Output by animal products ............... O u t p u t b y losses f r o m m a n u r e t o air, b e f o r e application . : ....................... Output by manure , ................... Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s o n g r a z e d areas . . . . . . . TOTAL SUPPLIES-REMOVALS

----

1.3

7.2 7.2

1.3

0.6

0.4

---

0.2

---0.9 1.3

7.3 7.9 0

0

-7.3 --

-0.9 ------

---7.0 7.2 0

Changes in a m o u n t o f total soil c o m p o n e n t SUPPLIES:

REMOVALS:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irn'gation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . by seed for sowing .............. TOTAL

2.5 35.8 -47.8

19. 20. 21. 22. 23. 28. 30.

O u t p u t by d e n i t r i f i c a t i o n . . . . . . . . . . . . . . . . Output by volatilization of ammonia ........ Output by leaching .................... O u t p u t by r u n - o f f o f available n u t r i e n t s . . . . . . Output by dust ...................... Output by organic matter, removed by run-off . . Transfer by net uptake from soil by plant ..... TOTAL

t 2.0 t t t t 43.7 45.7

SUPPLIES-REMOVALS

2.2 --

+2.1

t

--

7 ---t

7.6 -8.5 ---t t t 8.9 8.9 -0.4

39.5 -46.5 --(10) t t t 46.7 56.7 -10.2

253

TABLE 86 (continued) System type: Extensive livestock

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -1 y - i )

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no. Husz-1

Steppe and semi-desert, Patagonia

Nutrient

N

C h a n g e s in a m o u n t SUPPLIES:

REMOVALS:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer Transfer Transfer

19. 20. 21. 22. 23. 24. 25. 30t. 30r.

Output by denitrifieation ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y i m m o b i l i z a t i o n i n soil o r g a n i c f r a c t i o n Transfer by net uptake by the plant ......... Transfer by net uptake by the plant ......... TOTAL

by application of manure and/or waste . by droppings on grazed areas ....... application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... b y w e a t h e r i n g o f soil m i n e r a l f r a c t i o n . . b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n by plant production remaining on field . by seed for sowing .............. TOTAL

SUPPLIES-REMOVALS Changes in amount SUPPLIES:

REMOVALS:

12. Input by N-fixation by application and/or waste ........ by droppings on grazed areas ....... application of manure ............ application of litter, sludge and waste . b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n by plant products remaining on field . . TOTAL

Transfer Transfer Input by Input by Transfer Transfer

17. 28.

T r a n s f e r b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n Output by organic matter, removed by run-off., TOTAL SUPPLIES-REMOVALS

SUPPLY: REMOVAL:

24. 16.

K

--

--

------

-----

-2.5

t

----2.5 45 5.4 -55.4

7.0

t (1.0) 7.0 1.6 -9.6

t

--0

2.0

t

(20)

t 38 -65 --(10) t t

t t t

t t

-(10) 23.3 20.4 55.7

( )1.0 3.8 5.1 10.9

-21.2 25.5 64.7

- 0.3

-

+ 0.3

(1.0)

1.3

(8)

of soil organic matter

8b. 9b. 10b. 13b. 25. 26b.

C h a n g e s in a m o u n t

P

o f a v a i l a b l e soil n u t r i e n t s

--

2.2

---

4.8

0.9 --( 1.0) 6.0 7.9

-(TO) , 30.4 47.4 45 t

---

7.0 t

45

7.0

t --1.5 1.5 t t 0

+ 2.4

+ 0.9

+ 1.5

---

( (

1.0) 1.0)

(8.0) (20.0)

0

-12.0

o f soil m i n e r a l s T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y w e a t h e r i n g o f soil f r a c t i o n . . . . . . . SUPPLY-REMOVAL

0

254

T A B L E 87 System type: Extensive livestock

Summary of n u t r i e n t flows (units: kg h a - '

Type o f farm or e c o s y s t e m or type o f part o f a f a r m o r e c o s y s t e m , ref. n o . H u s z - 2

Shrub steppe (Monte) Argentina

Nutrient

N

y-' )

P

K

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

29. 30t. 30r. 31.

Input by Transfer Transfer Input by

seeds or seedlings . . . . . . . . . . . . . . . by net uptake from soil ........... by net uptake from soil ........... uptake from atmosphere .......... TOTAL

REMOVALS:

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. Transfer by plant production remaining on field . Transfer by seed for sowing .............. TOTAL

-16.7 -t 16.7

-3.3 --3.3

-33.4 --33.4

--

-1.0 -2.3 -3.3

-10.0 -23.4

5.0 -11.7 16.7

SUPPLIES-REMOVALS

0

0

33.4 0

C h a n g e s in a m o u n t o f a n i m a l c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4.

Input by Input by Transfer Transfer

5. 6.

Output by animal products ............... O u t p . u t b y losses f r o m m a n u r e t o air, b e f o r e application ......................... Output by manure .................... Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s o n g r a z e d areas . . . . . . . TOTAL

. • 9.

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

-. . . 5.0 5.0

--10.0 10.0

0.4

0.3

4.6 5.0

---0.7 1.0

9.8 10.0

0

0

-0.7 -----t 2.4 -3.1

-9.8 --

---

SUPPLIES-REMOVALS

---1.0 1.0

0

0.2 ---

Changes in amount of total soil component SUPPLIES:

REMOVALS:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . by seed for sowing .............. TOTAL

19. 20. 21. 22. 23. 28. 30.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off., Transfer by net uptake from soil by plant ..... TOTAL SUPPLIES-REMOVALS

-4.6 -2.5 -3 11.7 -21.8 t 2.3 t t t t

---

+28

t 23.5 -33.3

3.3 3.3

--t t t t 33.4 33.4

-0.2

-0.1

t t t t 16.7 19.0

---

255

ductivity (with soil improvement and fertilization) equals 3610 kg dry matter ha-1 y-1.

6.11.3.3. Table land, mid-Andes (Puna or altiplano) Classification. Extensive livestock. Reference: Husz-3; High table land, midAndes, 5% arable farming, 95% extensive livestock, Table 88.

Location: Situated between the t w o main crests of the mid-Andes (Peru, Bolivia), from a b o u t 5--27 ° SL. Altitude: 3400--4500 m. Climate: The mean annual temperature varies from 10 to 30°C, depending on the height and exposure. The mean annual range is 18--20°C. Annual precipitation, 10--75 cm, during the 3--4 summer months; mean precipitation: 69.3 cm; potential evapotranspiration: 91.8 cm; actual evapotranspiration: 53.4 cm. Soil: The landscape has a basin character. In large areas sediments can be found from former seas, which have disappeared as a result of tectonic movements. Everywhere the influence of volcanic ash and sand is obvious. Mollic Gleysols can be found in low-lying humid regions. In basins, salinization occurs and there is a build up of saline soils. On the flat slopes Mollic Andosols, Histosols and humic Cambisols predominate. In the basins, there are brown Kastanozems, whereas in the elevated parts Lithosols and Xerosols occur. The soils are mainly non-calcareous and mostly nutrient-poor (Ca, P). Soil productivity index, Qs = 0.425. Vegetation: Open shrub steppe, partly with "pillar" cacti and " t o l a " heath, 3400--4300 m (Fabiana densa, Psila boliviensis, Adesmia horridus cula, Junellia seriphoides, Baccharis incarum, Senecio viridus, Acantholippia hastulata, Tetrachlochin cristatum, NardophyUum armatum, Ephedra breana, Adesma spinosissima, Trichocereus pasacana, Parastrephia lepidophylla, Parastrephia phyllicaeformis). Open pastures (Pennisetum chilense, Festuca scirpifolia). Grass-steppes, > 4 3 0 0 m (Festuca ortophylla, Festuca chrysophylla, Poa gymnantha, Stipa ichu, Calamagrostis cabrera, Azoreila yareta, Apunthia atacamensis, Puya raimondis). Shoot index = 0.478. Use: Agriculture in the Puna is rather primitive, there is almost no import of fertilizers, seeds or herbicides, although it is n o t completely a self-sustaining system. Typical for the area is the weekly market where all kind of products are sold and bought, and this makes itdifficult to obtain reliable yield figures. A b o u t 5% of the area is used as arable land, partly applying fertilizers and herbicides, partly using lucerne, etc. The other 95% is used as extensive pastures with sheep, lama, and horned cattle. Phosphate is the factor limiting production. It allows only 183 kg (live weight) of animal growth ha -1, this figure being based on a P requirement of 15 g kg -1 live weight per year. On a yearly basis, o n l y 50% of the pastures are actually used: for the calculation of Table 88 therefore, only 91.5 kg live weight ha -1 is considered to be exported from the area.

256

TABLE 88 System type: Mixed farming

Summary of n u t r i e n t f l o w s ( u n i t s : k g h a -~ y - i )

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no. Husz-3

High table land, (Pura = altiplano, Paramos) 5% arable farming, 95% extensive livestock

Nutrient C h a n g e s in a m o u n t

N

P

K

-25.1 --25.1

-3.1 --3.1

-43.1 --43.1

0.5 11.9 0.8 11.9 -25.1

0.1 1.4 0.2 1.4 -3.1

1.5 20.6 0.4 20.6 -43.1

0

0

0

of plant component

SUPPLIES:

29. 30t. 30r. 31.

Input by Transfer Transfer Input by

seeds or seedlings ............... b y n e t u p t a k e f r o m soil . . . . . . . . . . . b y n e t u p t a k e f r o m soil . . . . . . . . . . . uptake from atmosphere .......... TOTAL

REMOVALS:

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products .............. T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g o n field . Transfer by seed for sowing .............. TOTAL SUPPLIES-REMOVALS

C h a n g e s in a m o u n t o f a n i m a l c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4.

Input by Input by Transfer Transfer

5. 6.

Output by animal products ............... Output by losses from manure to air, before application~li, ......................... Output by manure .................... Transfer by application of manure and/or waste . Transfer by droppings on grazed areas ....... TOTAL

7. 8. 9.

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

-. . .

--0.1 1.4 1.5

0.5 11.9 12.4 1.1

0.7

t -t 11.2 12.3

SUPPLIES-REMOVALS

--t 0.7 1.4

0

0

-1.5 20.6 22.1 0.4 --t 21.7 22,1 0

C h a n g e s in a m o u n t o f t o t a l soil c o m p o n e n t SUPPLIES:

REMOVALS:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . by droppings on grazed areas ....... application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . by seed for sowing .............. TOTAL

19. 20. 21. 22. 23. 28. 30.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off., T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL SUPPLIES-REMOVALS

0.25 11.2 -t 3 t -3.0 11.9 t 29.4

0.1 0.7 -t -t

0.12 21.7 -t -t

-t 1.4 t 2.2

t

--0

t 20.6 t 42.4

t t t 25.1 28.5

t t t 3.1 3.1

--t t t t 43.1 43.1

+0.9

-0.9

-0.7

3 0.5

257 Productivity and nutrient balance: The total dry matter production is 7558 kg ha-' y - ' , of which the above-ground part equals 3613 kg. With soil improvement and manuring the above-ground part rises to 7650 kg ha -~ y-1. 6.11.3.4. Shrub and tree savanna, Brazil The whole area is used for mixed farming. A distinction is made between areas receiving fertilizers and soil improvement, and areas without fertilizers and soil improvement. Both these areas are again split into a livestock part and an arable part. Thus in total, 6 systems have been defined. Classifica rio n: Mixed farming, Reference: Husz-4; Shrub and tree savannas, Central Brazil, no use of fertilizers or soil improvement, 25% cropped land and 75% grazed area, Table 90. Mixed, arable part. Reference: Husz-5; Shrub and tree savannas, Central Brazil, arable part of system Husz-4, Table 91. Mixed, livestock part. Reference: Husz-6; Shrub and tree savannas, Central Brazil, livestock part of system Husz-4, Table 92. Intensive mixed farming. Reference: Husz-7; Shrub and tree savannas, Central Brazil, with soil improvement and fertilizers, 50% cropped land, 50% livestock area, Table 93. Intensive, mixed, arable part. Reference: Husz-8; Shrub and tree savannas, Central Brazil, arable part of system Husz-7, Table 94. Intensive, mixed, livestock part. Reference: Husz-9; Shrub and tree savannas, Central Brazil, livestock part of system Husz-7, Table 95. Location: Central Brazilian plateau, mid-Brazil, Altitude 200--600 m. Climate: Mean annual temperature: 24--27°C; average temperature range: 5°C; annual precipitation: 110--220 cm; mean precipitation: 127.2 cm; potential evapotranspiration: 330.2 cm; actual evapotranspiration: 24.9 cm. Soil: Although the landscape is geologically older, the tertiary erosion products and sediments (frequently sandstone from the upper Cretaceous) predominate at the soil surface. The tertiary sediments are extremely weathered. The soils on this material are Acric Ferrasols ~md they belong to the oldest known soil formations. The soils formed from the sandstone of the Cretaceous sediments are developed as Lithosols or ferralic Arenosols. During the Quarternary period, the old landscape was altered once again. The soils resulting from sediments which were rearranged in the youngest geological era would appear to be Cambic or Argillic B-horizons. Main soils: Orthic Acrisols together with Ferric Luvisols, Eutric Nitrosols, Chromic Luvisols and Dystric Cambisols. Productivity index Qs = 0.50. Vegetation: Savannas of the "Campos Cerrados" (characteristic sorts of trees and shrubs) and gallery woods. Use: From a climatic point of view the production potential is high. However, the precipitation of 1200 mm annually and its distribution limit produc-

258 tion. The mean shoot index is 0.478. The area is covered with savannas and gale forests; agriculture is only possible on selected areas, where the production of tropical and subtropical crops such as coffee, citrus, c o t t o n and sugar cane is possible. Intensive fertilizer dressings are used on the plantations, b u t on the areas belonging to small sociological units (families) fertilization practices vary enormously. The main products of the small farms are fruit, corn, beans, potatoes, and sweet potatoes. Livestock consists of horned cattle, pigs, horses and poultry. Productivity and nutrient balance: Nutrient balances have been prepared for the small farms; irrigated areas and plantations are n o t considered. No data for nutrient balances for separate farms are available, so that values again had to be calculated. For the system described by Husz-4 (no fertilizers, no soil improvement), Qs was taken to be 0.50, giving an above-ground dry matter production of 8266 kg ha -1 . For the system Husz-5 (with fertilizers and soil improvement), Qs was set at 0.85, giving an above-ground dry matter production of 14052 kg ha-~. To calculate the figures in the nutrient balance tables, the nutrient content of the crops was taken as: 10 kg N, 1.2 kg P and 12 kg K per 1000 kg dry matter. The percentage of plant parts remaining in the field was set at 20%, a further 57% went to the market, and the share of animal and human consumption was 22% and 1%, respectively. The actual figures for nitrogen are presented in Table 89, and the mutual relationships between the fluxes are shown in Fig. 41. An analysis of the nitrogen fluxes of system Husz-4, Tables 90--92, shows a shortage of nitrogen on the livestock area. This results from the assumption that an important part of the excrements are transferred to the arable area. If this is not done, the shortage of nitrogen occurs on the arable part of the farm. In such situations it is customary to alternate the arable land and the pastures from time to time. System Husz-5, Table 91 (see also Tables 89, 93, 94 and 95), shows a flow of nitrogen, in the form of feed for cattle, from the arable part to the pastures. The return flow (application of manure to arable land) is absent, resulting in a nitrogen deficit for the arable part of the farm, in spite of the

561 (Import)

j

(Export)

SOIL

Fig. 41. Nitrogen flow chart, small farm, central Brazil (system Husz-7). Values are in kg and refer to 0.5 ha pasture plus 0.5 ha cropped land.

1.46 35.95 45.65 97.11

Total

14.05

Uptake by vegetation Feed for cattle Crops sold Private consumption (crops) Remaining on field Grazing Uptake by livestock Livestock sold Private consumption (meat) Waste Excrements Input fertilizers 97.11

26.86

70.25

97.11

26.86

70.25

In

In

Out

Plant

Soil

97.11

26.86

15.45 40.04 0.71

Out

42.31

26.86

14.05

15.45

In

Animal

42.31

35.95

5.61 0.75

Out

1.46

0.75

0.71

In

Human

1.46

1.46

Out

45.65

45.65

Import

45.65

5.61

40.04

Export

Nitrogen balance of small farms, central Brazil (system Husz-7 ). The ratio between arable land and pastures is 1:1. Note that the values are expressed per ha total area, so that the actual values per ha arable land or pasture have to be doubled. E.g. the uptake is 140.5 kg N ha -1 (twice the 70.25 kg of the table)

TABLE 89

t,O ¢J1 ¢O

260

TABLE 90 System type: Extensive mixed farming

Summary of nutrient flows (units: kg ha-'

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no. Husz-4

S h r u b a n d t r e e s a v a n n a s , C e n t r a l Brazil, 25% cropped land, 75% livestock area

Nutrient C h a n g e s in a m o u n t SUPPLIES:

REMOVALS:

29. 30t. 30r. 31. 3. 4. 18. 26. 27.

y-' )

N

P

K

t

t

t

of plant component Input by Transfer Transfer Input by

seeds or seedlings ............... b y n e t u p t a k e f r o m soil . . . . . . . . . . . b y n e t u p t a k e f r o m soil . . . . . . . . . . . uptake from atmosphere .......... TOTAL

56.9 -t

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ............. Output by primary products . Transfer by plant production remaining'on'fieid ~ Transfer by seed for sowing .............. TOTAL

9.5 -t

95.1 -t

56.9

9.5

95.1

2.3 40.3 11.0 3.3 -56.9

0.3 7.4 1.4 0.4 -9.5

2.8 74.4 13.7 4.2 -95.1

SUPPLIES-REMOVALS

0

0

0

C h a n g e s in a m o u n t o f a n i m a l c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4.

Input by Input by Transfer Transfer

. . .

1.7 40.3 42.0

--0.2 7.5 7.7

5. 6.

Output by animal products ............... Output by losses from manure to air, before application~ . . . . . . . . . . . . . . . . . . . . . . . . . Output by manure .................... Transfer by application of manure and/or waste . Transfer by droppings on grazed areas ....... TOTAL

9.6

3.3

7. 8. 9.

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

---

--

SUPPLIES:

REMOVALS:

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

19. 20. 21.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust ...................... Output by organic matter, removed by run-off., T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL

22.

6.3

t 1.7 30.7 42.0

-t

0.9 3.5 7.7

1.4 68.7 76.4

0

0

0

2.3 30.6 --6.0

1.0 3.5 ----

2.2 68.7 ---t -t 4.1 t 75

o f t o t a l soil c o m p o n e n t

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

23. 28. 30.

2.1 74.3 76.4

--

t

SUPPLIES-REMOVALS C h a n g e s in a m o u n t

---

by application of manure and/or waste . by droppings on grazed areas ....... application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste irrigation and flooding .......... : dry and wet deposition ........... by plant products remaining on field . . by seed for sowing .............. TOTAL

SUPPLIES-REMOVALS

t

t --

-6.0 3.3

t

t 0.4 t

48.2

4.9

1.0 3.7 t t t t

--t t t t

--t t t t

56.9 61.6

9.5 9.5

95.1 95.1

-13.4

-4.6

-20.1

261

T A B L E 91 S y s t e m t y p e : Extensive m i x e d f a r m i n g

S u m m a r y of n u t r i e n t flows (units: kg ha - I y - i )

T y p e o f f a r m or e c o s y s t e m or t y p e o f p a r t o f a f a r m or e c o s y s t e m , ref. no. Husz-5

S h r u b and tree savannas, Central Brazil, N balance arable part o f s y s t e m Husz-4

Nutrient

N

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

29. 30t. 30r. 31.

Input by Transfer Transfer Input by

seeds or seedlings . . . . . . . . . . . . . . . by n e t u p t a k e f r o m soil . . . . . . . . . . . by n e t u p t a k e f r o m soil . . . . . . . . . . . uptake from atmosphere .......... TOTAL

t 66.1 --66.1

REMOVALS:

3. 4. 18. 26. 27.

T r a n s f e r b y c o n s u m p t i o n o f h a r v e s t e d crops . . . T r a n s f e r b y grazing o f forage . . . . . . . . . . . . . Output by primary products . . . . . . . . . . . . . . T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g on field . T r a n s f e r b y seed for s o w i n g . . . . . . . . . . . . . . TOTAL

9.0 -43.9 13.2 -66.1

SUPPLIES-REMOVALS

0

Changes in a m o u n t o f a n i m a l c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4.

I n p u t b y feed for livestock . . . . . . . . . . . . . . . I n p u t by litter used indoors . . . . . . . . . . . . . . Transfer by consumption of harvested crops T r a n s f e r by grazing of forage . . . . . . . . . . . . . TOTAL

5. 6.

Output by animal products . . . . . . . . . . . . . . . O u t p u t b y losses f r o m m a n u r e to air, b e f o r e application . . . . . . . . . . . . . . . . . . . . . . . . . Output by manure . . . . . . . . . . . . . . . . . . . . Transfer by application of manure and/or waste . T r a n s f e r b y d r o p p i n g s on grazed areas . . . . . . . TOTAL

7. 8. 9.

. . .

SUPPLIES-REMOVALS Changes in a m o u n t o f total soil c o m p o n e n t SUPPLIES:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

R E M O V A L S : 19. 20. 21. 22. 23. 28. 30.

T r a n s f e r b y application o f m a n u r e a n d / o r waste . T r a n s f e r b y droppings on grazed areas . . . . . . . I n p u t by application o f m a n u r e . . . . . . . . . . . . I n p u t by fertilizers . . . . . . . . . . . . . . . . . . . . I n p u t by N-fixation . . . . . . . . . . . . . . . . . . . . I n p u t by application o f litter, sludge and w a s t e . I n p u t b y irrigation and flooding . . . . . . . . . . . I n p u t by d r y and w e t d e p o s i t i o n . . . . . . . . . . . T r a n s f e r by p l a n t p r o d u c t s r e m a i n i n g on field . . T r a n s f e r by seed for sowing . . . . . . . . . . . . . . TOTAL

--51.7 -t t t 5.3 13.2 -70.2

O u t p u t b y denitrification . . . . . . . . . ~. . . . . . . O u t p u t b y volatilization o f a m m o n i a . . . . . . . . O u t p u t b y leaching . . . . . . . . . . . . . . . . . . . . O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . O u t p u t by dust . . . . . . . . . . . . . . . . . . . . . . O u t p u t by organic m a t t e r , r e m o v e d b y r u n - o f f . , T r a n s f e r by n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL

t

SUPPLIES-REMOVALS

3 1 t t t 66.1 70.1 0

P

K

262

T A B L E 92 S y s t e m t y p e : Extensive m i x e d f a r m i n g

Summary of n u t r i e n t flows (units: kg ha -~ y-~ )

T y p e o f f a r m or e c o s y s t e m or t y p e of p a r t of a f a r m or e c o s y s t e m , ref. no. Husz-6

S h r u b and tree savannas, Central Brazil, N balance livestock part o f s y s t e m Husz-4

Nutrient

N

P

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

29. 30t. 30r. 31.

I n p u t by seeds or seedlings . . . . . . . . . . . . . . . T r a n s f e r by n e t u p t a k e f r o m soil . . . . . . . . . . . T r a n s f e r b y n e t u p t a k e f r o m soil . . . . . . . . . . . I n p u t by u p t a k e f r o m a t m o s p h e r e . . . . . . . . . . TOTAL

-53.7 --

REMOVALS:

3. 4. 18. 26. 27.

T r a n s f e r by c o n s u m p t i o n o f h a r v e s t e d crops . . . T r a n s f e r by grazing o f forage . . . . . . . . . . . . . O u t p u t by p r i m a r y p r o d u c t s . . . . . . . . . . . . . . T r a n s f e r by p l a n t p r o d u c t i o n r e m a i n i n g on field . T r a n s f e r by seed for s o w i n g . . . . . . . . . . . . . . TOTAL

-

53.7 53.7 -t 53.7

SUPPLIES-REMOVALS

0

Changes in a m o u n t o f animal c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4.

I n p u t by feed for livestock . . . . . . . . . . . . . . . I n p u t b y litter used indoors . . . . . . . . . . . . . . T r a n s f e r b y c o n s u m p t i o n o f harvested crops T r a n s f e r by grazing o f forage . . . . . . . . . . . . . TOTAL

5. 6.

O u t p u t by animal p r o d u c t s . . . . . . . . . . . . . . . Out~.ut b y losses f r o m m a n u r e to air, b e f o r e application . . . . . . . . . . . . . . . . . . . . . . . . . O u t p u t by m a n u r e . . . . . . . . . . . . . . . . . . . . T r a n s f e r b y application o f m a n u r e a n d / o r waste . T r a n s f e r by droppings on grazed areas . . . . . . . TOTAL

7. 8. 9.

2.2 -. . .

SUPPLIES-REMOVALS

53.7 55.9 12.9 -17.2 2.3 23.6 55.6 t

Changes in a m o u n t o f total soil c o m p o n e n t SUPPLIES :

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

R E M O V A L S : 19. 20. 21. 22. 23. 28. 30.

T r a n s f e r b y application o f m a n u r e a n d / o r w a s t e . T r a n s f e r b y droppings on grazed areas . . . . . . . I n p u t b y application o f m a n u r e . . . . . . . . . . . . I n p u t by fertilizers . . . . . . . . . . . . . . . . . . . . I n p u t b y N-fixation . . . . . . . . . . . . . . . . . . . . I n p u t b y application o f litter, sludge and w a s t e . I n p u t b y irrigation a n d flooding . . . . . . . . . . . I n p u t b y d r y and w e t d e p o s i t i o n . . . . . . . . . . . T r a n s f e r b y p l a n t p r o d u c t s r e m a i n i n g on field . . T r a n s f e r b y seed for s o w i n g . . . . . . . . . . . . . . TOTAL

2.3 23.6 --8.0 t t 7.0 -t 40.9

O u t p u t by denitrification . . . . . . . . . . . . . . . . O u t p u t b y volatilization o f a m m o n i a . . . . . . . . O u t p u t by leaching . . . . . . . . . . . . . . . . . . . . O u t p u t by r u n - o f f o f available n u t r i e n t s . . . . . . O u t p u t b y dust . . . . . . . . . . . . . . . . . . . . . . O u t p u t by organic m a t t e r , r e m o v e d b y r u n - o f f . , T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL

t t t t

SUPPLIES-REMOVALS

t 4.0

53.7 57.7 -17.2

K

263

T A B L E 93 System type: Intensive mixed farming

Summary of n u t r i e n t f l o w s ( u n i t s : k g ha - I y - i )

T y p e o f f a r m o r e c o s y s t e m or t y p e o f p a r t o f a f a r m or e c o s y s t e m , ref. no. Husz-7

S h r u b a n d t r e e s a v a n n a s , Central Brazil, w i t h soil i m p r o v e m e n t a n d fertilizers, 50% arable f a r m i n g , 50% l i v e s t o c k f a r m i n g

Nutrient

N

P

K

t

t 177.1 --

97.1

t 17.6 --17.6

16.1 26.9 40.0 14.1 -97.1

3.9 5.0 7.2 2.5 -18.6

21.3 84.3 52.2 193 -177.1

C h a n g e s in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

REMOVALS:

29. 30t. 30r. 31.

Input by Transfer Transfer I n p u t by

seeds or seedlings . . . . . . . . . . . . . . . by n e t u p t a k e f r o m soil . . . . . . . . . . . by n e t u p t a k e f r o m soil . . . . . . . . . . . uptake trom atmosphere .......... TOTAL

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . Transfer by grazing of forage . . . . . . . . . . . . . Output by primary products .............. T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g on field . Transfer by seed for sowing . . . . . . . . . . . . . . TOTAL

97.1 --

SUPPLIES-REMOVALS

0

177.1

t

0

C h a n g e s in a m o u n t o f a n i m a l c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4.

Input by Input by Transfer Transfer

5. 6.

O u t p u t by a n i m a l p r o d u c t s . . . . . . . . . . . . . . . O u t p u t by losses f r o m m a n u r e to air, b e f o r e application . . . . . . . . . . . . . . . . . . . . . . . . . O u t p u t by m a n u r e . . . . . . . . . . . . . . . . . . . . Transfer by application of manure and/or waste . T r a n s f e r by d r o p p i n g s on g r a z e d areas . . . . . . . TOTAL

7. 8. 9.

feed f o r l i v e s t o c k . . . . . . . . . . . . . . . l i t t e r used i n d o o r s . . . . . . . . . . . . . . by consumption of harvested crops by grazing of forage . . . . . . . . . . . . . TOTAL

--

--

t . . .

SUPPLIES-REMOVALS

t 15.4 26.9 42.3 5.7

3.8

0.8 36 42.5

--0.2 3.8 7.8

---

t

-t

2.8 5.0 7.8

20.4 84.3 104.7 7.1 --0.6 97.0 104.7

0

0

0.3 3.8 -11 -t -t 2.5 t 17.6

1.6 97 -59.3 --

C h a n g e s in a m o u n t o f total soil c o m p o n e n t SUPPLIES:

8.

9. 10. 11. 12. 13. 14. 15. 26. 27. R E M O V A L S : 19. 20. 21. 22. 23. 28. 30.

Transfer Transfer Input by Input by Input by Input by I n p u t by Input by Transfer Transfer

by a p p l i c a t i o n o f m a n u r e a n d / o r w a s t e . by d r o p p i n g s on g r a z e d areas . . . . . . . application of manure . . . . . . . . . ... fertilizers . . . . . . . . . . . . . . . . . . . . N-fixation .................... a p p l i c a t i o n o f litter, sludge a n d w a s t e . irrigation and flooding . . . . . . . . . . . dry and wet deposition . . . . . . . . . . . b y p l a n t p r o d u c t s r e m a i n i n g on field . . b y seed f o r s o w i n g . . . . . . . . . . . . . . TOTAL

O u t p u t by d e n i t r i f i c a t i o n . . . . . . . . . . . . . . . . O u t p u t by v o l a t i l i z a t i o n o f a m m o n i a . . . . . . . . O u t p u t by l e a c h i n g . . . . . . . . . . . . . . . . . . . . O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . Output by dust ...................... O u t p u t by o r g a n i c m a t t e r , r e m o v e d b y r u n - o f f . , T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL SUPI~LIES-REMOVALS

1.5 36.0 -45.7 21 t -10 14.1 t 128.3 2 18 1 t t t 97.1 118.1 10.2

t -t 19.3 t 177.2

--0 t t t 17.6 17.6

--t t t t 177.1 177.1

0

+ 0.1

264

T A B L E 94 S y s t e m t y p e : Intensive m i x e d f a r m i n g

Summary of n u t r i e n t . f l o w s (units: kg ha -1 y-~ )

T y p e o f f a r m o r e c o s y s t e m or t y p e o f part o f a f a r m or e c o s y s t e m , ref. no. Husz-8

S h r u b and tree savannas, Central Brazil, with soil i m p r o v e m e n t and fertilizers, N balance arable part o f s y s t e m Husz-7

Nutrient

N

P

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

29. 30t. 30r. 31.

I n p u t b y seeds or seedlings . . . . . . . . . . . . . . . T r a n s f e r b y n e t u p t a k e f r o m soil . . . . . . . . . . . T r a n s f e r b y n e t u p t a k e f r o m soil . . . . . . . . . . . Input by uptake from atmosphere . . . . . . . . . . TOTAL

-141 --141

REMOVALS:

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . T r a n s f e r b y grazing o f forage . . . . . . . . . . . . . Output by primary products Transfer by plant production remaining on field . Transfer by seed for sowing . . . . . . . . . . . . . . TOTAL

--113 28 -141

SUPPLIES-REMOVALS

0

Changes in a m o u n t of animal c o m p o n e n t SUPPLIES:

1. 2. 3. 4.

Input by Input by Transfer Transfer

REMOVALS:

5. 6.

Output by animal products . . . . . . . . . . . . . . . Output by losses from m a n u r e to air, before application . . . . . . . . . . . . . . . . . . . . . . . . . Output by m a n u r e . . . . . . . . . . . . . . . . . . . . T r a n s f e r by application o f m a n u r e a n d / o r w a s t e . T r a n s f e r b y droppings on grazed areas . . . . . . . TOTAL

7. 8. 9.

feed for livestock . . . . . . . . . . . . . . . litter used indoors . . . . . . . . . . . . . . b y consumption of harvested crops . . . by grazing of forage . . . . . . . . . . . . . TOTAL

SUPPLIES-REMOVALS Changes in a m o u n t o f total soil c o m p o n e n t SUPPLIES:

8. T r a n s f e r b y application o f m a n u r e a n d / o r w a s t e . 19"0. T r a n s f e r by d r o p p i n g s on grazed areas . . . . . . . I n p u t by application o f m a n u r e . . . . . . . . . . . . 11. I n p u t by fertilizers . : . . . . . . . . . . . . . . . . . . 12. I n p u t b y N-fixation . . . . . . . . . . . . . . . . . . . . 13. I n p u t by application o f litter, sludge and w a s t e . 14. I n p u t by irrigation and flooding . . . . . . . . . . . 15. I n p u t b y d r y and w e t deposition . . . . . . . . . . . 26. T r a n s f e r b y p l a n t p r o d u c t s r e m a i n i n g on field • . 27. T r a n s f e r by seed for s o w i n g . . . . . . . . . . . . . . TOTAL

R E M O V A L S : 19. 20. 21. 22. 23. 28. 30.

-91 17 --10 20 -138

O u t p u t b y denitrification . . . . . . . . . . . . . . . . O u t p u t b y volatilization o f a m m o n i a . . . . . . . . O u t p u t b y leaching . . . . . . . . . . . . . . . . . . . . O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . O u t p u t by dust . . . . . . . . . . . . . . . . . . . . . . O u t p u t b y organic m a t t e r , r e m o v e d b y r u n - o f f . . T r a n s f e r by n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL

2 15 1 ---141 159

SUPPLIES-REMOVALS

-21

K

265

T A B L E 95 S y s t e m t y p e : Intensive m i x e d f a r m i n g

S u m m a r y of n u t r i e n t flows (units: kg ha - l y - l )

T y p e o f f a r m or e c o s y s t e m o r t y p e o f p a r t o f a f a r m or e c o s y s t e m , ref. no. Husz-9

S h r u b and tree savannas, Central Brazil, with soil i m p r o v e m e n t and fertilizers, N-balance livestock p a r t o f s y s t e m Husz-7

Nutrient

N

P

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

29. 30t. 30r. 31.

I n p u t b y seeds or seedlings . . . . . . . . . . . . . . . T r a n s f e r by n e t u p t a k e f r o m soil . . . . . . . . . . . T r a n s f e r by n e t u p t a k e f r o m soil . . . . . . . . . . . I n p u t by u p t a k e f r o m a t m o s p h e r e . . . . . . . . . . TOTAL

-54 --54

REMOVALS:

3. 4. 18. 26. 27.

T r a n s f e r by c o n s u m p t i o n o f h a r v e s t e d crops . . . T r a n s f e r b y grazing o f forage . . . . . . . . . . . . . O u t p u t by p r i m a r y p r o d u c t s . . . . . . . . . . . . . . T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g on field . T r a n s f e r b y seed for s o w i n g . . . . . . . . . . . . . . TOTAL

-54 --

SUPPLIES-REMOVALS

0

-54

Changes in a m o u n t o f animal c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4.

I n p u t b y feed for livestock . . . . . . . . . . . . . . . I n p u t by litter used i n d o o r s . . . . . . . . . . . . . . T r a n s f e r by c o n s u m p t i o n o f h a r v e s t e d crops T r a n s f e r b y grazing o f forage . . . . . . . . . . . . . TOTAL

5. 6.

Output by animal products . . . . . . . . . . . . . . . O u t p u t b y losses f r o m m a n u r e to air, b e f o r e • application . . . . . . . . . . . . . . . . . . . . . . . . . Output by manure . . . . . . . . . . . . . . . . . . . . T r a n s f e r b y application o f m a n u r e a n d / o r w a s t e . T r a n s f e r b y droppings on grazed areas . . . . . . . TOTAL

7. 8. 9.

. . .

SUPPLIES-REMOVALS

31 --54 85 11 -2 72 85 0

Changes in a m o u n t o f t o t a l soil c o m p o n e n t SUPPLIES:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

R E M O V A L S : 19. 20. 21. 22. 23. 28. 30.

T r a n s f e r by application o f m a n u r e a n d / o r waste . T r a n s f e r by droppings on grazed areas . . . . . . . I n p u t by application o f m a n u r e . . . . . . . . . . . . I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . I n p u t b y N-fixation . . . . . . . . . . . . . . . . . . . . I n p u t by a p p l i c a t i o n o f litter, sludge and w a s t e . I n p u t by irrigation and flooding . . . . . . . . . . . I n p u t b y d r y and w e t deposition . . . . . . . . . . . T r a n s f e r b y p l a n t p r o d u c t s r e m a i n i n g on field . . T r a n s f e r b y seed for s o w i n g . . . . . . . . . . . . TOTAL O u t p u t b y denitrification . . . . . . . . . . . . . . . . O u t p u t b y volatilization o f a m m o n i a . . . . . . . . O u t p u t b y leaching . . . . . . . . . . . . . . . . . . . . O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . O u t p u t b y dust . . . . . . . . . . . . . . . . . . . . . . O u t p u t b y organic m a t t e r , r e m o v e d b y r u n - o f f T r a n s f e r by n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL

2 72 -25 -10 -109 2 20 1 --

.

SUPPLIES-REMOVALS

.

54 77 32

K

266

fact that the fertilizers are applied to the arable area and n o t to the livestock area. Literature: Jenny, 1941, 1964; Fried and Broeshart, 1967; Stevensen, 1965.

6.11.3.5. Arid and mesophytic transitional woods Classification: Mixed livestock. Reference: Husz-10; Arid and mesophytic transitional woods, S. America, all kinds of products ; ratio pastures : cropped land = 4:1, Table 96. Location: The arid woods and transitional forms to mesophytic woods are widely spread over this continent, on low plateaus and western slopes of the Andes (northern Chile, southern Peru), at altitudes of 500--1500 m. They also occur in the central Chaco from Santa Cruz de la Sierra, Bolivia, to Mar Chicita in Argentina (altitude 60--400 m), on the western edge of the Chaco (Argentina and Bolivia, altitude 100--500 m), in the eastern Chaco (altitude 60--200 m), in the area of the Parana (Paraguay and Uruguay, altitude 20-100 m), in the area between the Rio Negro and Cordoba in mid-Argentina (0--400 m), in the Caatinga area (northwestern Brazil, 0--500 m) and in the Caribbean coast area, both in the valleys of the Andes with a semi-arid character and the coast area from northern Peru to southern Ecuador. Climate: Mean annual temperature: 16--29°C; mean annual range: 14°C; annual precipitation: 30--150 cm; mean precipitation: 76.8 cm; mean potential evapotranspiration: 187.8 cm; actual evapotranspiration: 75.8 cm. Soil: Most sediments of these plateaus are weathered parts of an old mountainous area. They form the present-day soil, although the original material (mainly of a sandy nature), which is usually displaced, has been changed a great deal due to tectonic movements and weathering. On the western slopes of the Andes Orthic Ferralsols, Xanthic soils, Albic Arenosols and Plinthic Acrisols are found (altitude: 60--400 m, temperature: 16--21°C + 15, annual precipitation: 50--80 cm). Apart from the frequently occurring transition forms, the soils are mainly Acric Ferralsols, Orthic Acrisols and Ferralic Arenosols over the main part of the area, and, in the valley plains, both Ferric Luvisols and Gleysols within the reach of groundwater. The well known "Caatinga-lat sol" can be equated to an Orthic Ferralsol. In eroded areas, where ancient soils are removed, Rhodic Ferralsols and Eutric Nitrosols (= "Terra R o x a Estructurada") can be found, occurring on older geological material on solid rock {basalt). Vegetation: To describe the vegetation types, it is necessary to specify areas which can be distinguished. (a) Southwestwards from the Andes in northern Chile and in Peru. Altitude: 500--1500 m. Climate: mean annual temperature, 16--21°C + 7; precipitation 3 0 - 1 0 0 cm. Main vegetation: open arid brushwood with "pillar" cacti. Use: firewood; with irrigation: sugar-cane, cotton, rice, lucerne, maize.

267 (b) Arid woods of the Central Chaco. (The Central Chaco runs from Santa Cruz de la Sierra, Bolivia, to the Mar Chiquita, Argentina.) Altitude: 100--400 m. Climate: mean annual temperature, 20--24°C; mean annual range, 15°C; annual precipitation, 50--80 cm. Main vegetation: "Algarrobowood". Use: forestry, charcoal ("Fannin"), cattle, goats, sheep, cotton, maize, lucerne. (c) Arid woods to rather fresh woods of the eastern part of the Chaco (eastern Chaco in Paraquay and Argentina). Altitude: 60--200 m. Climate: mean annual temperature, 24--25°C; mean annual range, 6°C; annual precipitation, 110--120 cm. Main vegetation: Quebracho-wood, Schinopsis balansae (Quebracho colorado diaque~o), Schinus molle (molle, pimiento), Copernicia australis (caranday), plus vegetation as in the Central Chaco. Use: as in the Central Chaco. (d) Mesophytic transitional woods of the western Chacorandes (western edge of the Chaco in Argentina and Bolivia). Altitude: 100--150 m. Climate: mean annual temperature, 19--20°C; mean annual range, 13°C; annual precipitation, 70--100 cm. Main vegetation: Tala-Mistol wood. Use: forestry, sugar-cane, maize, lucerne, potatoes, tobacco, citrus, vegetables. (e) Park landscape of Entre Rios (Parque mesopot~mico) (eastern Chaco border area in reach of the Parana, Paraguay and upper Uruguay). Altitude: 20--100 m. Climate: mean annual temperature, 17--21°C; mean annual range, 12°C; annual precipitation, 100--140 cm. Main vegetation: subtropical woods, gallery woods, semi-arid and arid woods, palm woods, savannas within reach of the groundwater, rush-moors. Use: forestry, cattle, sheep, rice, cotton, jute, tobacco, fruit, wheat, maize, oats, lucerne, ground-nuts, sunflowers. (f) Arid woods of the Espinales and transition from arid woods to Monte vegetation (mid-Argentina between Rio Negro and Cordoba). Altitude: 0--400 m. Climate: mean annual temperature, 14--18°C; mean annual range, 14°C; annual precipitation, 30--60 cm. Main vegetation: arid woods, palm woods, Monte shrub-steppe. Use: firewood, cattle, horses, lucerne. (g) Vegetation of arid valleys of the Andes (valleys of the Andes from northern Argentina to Venezuela). Altitude: 400--2000 m.

268 Climate: mean annual temperature depending on latitude and height, between 16 and 27°C; annual precipitation, 30--80 cm. Main vegetation: in Argentinian and Bolivian part: algarrobo woods and halophyte vegetation; in Peruvian, Ecuadorian, Columbian and Venezuelian part: arid woods. Use: firewood, cattle, goats, sheep, maize, wheat, rice, cotton, cocoa, fruit, vineyards. (h) Caribbean arid woods, mainly thorn bushes and cactus bushes (Caribbean coastal area of Columbia, Venezuela and neighbouring islands). Altitude: 0--500 (1000) m. Climate: mean annual temperature, 24--29°C; mean annual range, 1--2°C; annual precipitation, 30--80 cm. Main vegetation: thorn bushes, cacti, brushwoods. Use: firewood, cattle, goats, maize, cotton. (i) Caatinga (northeastern Brazil). Altitude: 0--500 m. Climate: mean annual temperature, 24--26°C; mean annual range, 1°C; annual precipitation, 30--80 cm. Main vegetation: arid woods and arid bushes of the Caatinga, gallery woods, arid grassland, savannas. Use: forestry, palm culture, palm oil, cattle, goats, sheep, hogs, donkeys, mules. (j) Agreste woods (between Atlantic coastal mountains and Caatinga). Altitude: 0 - 5 0 0 (1000) m. Climate: mean annual temperature, 25°C, mean annual range, 1°C; mean annual precipitation, 30--80 cm. Main vegetation: Agreste arid woods, palms. (k) Espinal of the mouth of the Plata (lower Parana, with delta). Altitude: 0--100 m. Climate: mean annual precipitation, 17°C; mean annual range, 12°C; annual precipitation, 80--100 cm. Main vegetation: thorn brushwoods, willow woods, tessaria woods, pithecolobium woods, saphium woods, erythrina woods, palm woods. Use: fruit culture. Productivity and nutrient balance: In this whole area forestry is important: the nutrient balance applies however to the (extensive) mixed farming which is carried out near villages. The ratio between pastures and cropped land can be taken as 4:1. The calculations are based on a mean yield of 5945 kg ha-' above-ground dry matter, and a soil productivity index Qs of 0.605. The total dry matter production is 14 940 kg ha-' without soil improvement (shoot index Qv = 0.398).

269

T A B L E 96 System type: Extensive mixed farming

Summary of n u t r i e n t f l o w s ( u n i t s : kg ha -1 y - i )

T y p e o f f a r m or e c o s y s t e m or t y p e o f p a r t o f a f a r m or e c o s y s t e m , ref. no. Husz-10

A r i d + mesot~hytic t r a n s i t i o n a l w o o d s , S. A m e r i c a , all k i n d o f p r o d u c t s , r a t i o past u r e s : c r o p p e d land = 4 : 1

Nutrient

N

P

K

-40.9 --

-68.4 --

40.9

-6.9 --6.9

1.6 29.0 7.9 2.4 -40.9

0.2 5.4 1.0 0.3 -6.9

2.0 53.5 9,9 3.0 -68,4

C h a n g e s in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES :

29. 30t. 30r. 31.

Input by Transfer Transfer Input by

s e e d s or s e e d l i n g s . . . . . . . . . . . . . . . by n e t u p t a k e f r o m soil . . . . . . . . . . . b y n e t u p t a k e f r o m soil . . . . . . . . . . . uptake irom atmosphere .......... TOTAL

REMOVALS:

3. 4. 18. 26. 27.

Transfer by consumption of harvested crops . . . Transfer by Gazing of forage . . . . . . . . . . . . . Output by primary products .............. T r a n s f e r by p l a n t p r o d u c t i o n r e m a i n i n g on field . T r a n s f e r by seed f o r s o w i n g . . . . . . . . . . . . . . TOTAL SUPPLIES-REMOVALS

68.4

0

0

0

--1.2 29.0 30.2

--0.2 5.4 5.6

6.9

2.4

--1.2 22.0 30.1

--0.6 2.5 5.5

+0.1

+0.1

0

1.7 21.9 -t 8 t t 15 2.4 t 49

0.7 2.5 --

1.6 49.5 --

C h a n g e s in a m o u n t o f a n i m a l c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4.

Input by Input by Transfer Transfer

5. 6.

Output by animal products ............... O u t p u t b y losses f r o m m a n u r e to air, b e f o r e application~i ......................... O u t p u t by m a n u r e . . . . . . . . . . . . . . . . . . . . Transfer by application of manure and/or waste . T r a n s f e r by d r o p p i n g s o n g r a z e d areas . . . . . . . TOTAL

7. 8. 9.

feed f o r l i v e s t o c k . . . . . . . . . . . . . . . l i t t e r used i n d o o r s . . . . . . . . . . . . . . by c o n s u m p t i o n o f h a r v e s t e d crops by g r a z i n g o f f o r a g e . . . . . . . . . . . . . TOTAL

.

.

.

SUPPLIES-REMOVALS

-1.5 53.5 55,0 4,5 --1.0 49.5 55

C h a n g e s in a m o u n t o f total soil c o m p o n e n t SUPPLIES:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

R E M O V A L S : 19. 20. 21. 22. 23. 28. 30.

Transfer Transfer Input by Input by Input by Input by Input by I n p u t by Transfer Transfer

by application of manure and/or waste . b y d r o p p i n g s on g r a z e d areas . . . . . . . application of manure . . . . . . . . .... fertilizers . . . . . . . . . . . . . . . . . . . . N-fixation .................... a p p l i c a t i o n o f litter, sludge and w a s t e . irrigation and flooding . . . . . . . . . . . dry and wet deposition . . . . . . . . . . . b y p l a n t p r o d u c t s r e m a i n i n g on field . . by seed f o r s o w i n g . . . . . . . . . . . . . . TOTAL

Output by denitrification ................ O u t p u t by v o l a t i l i z a t i o n o f a m m o n i a . . . . . . . . O u t p u t by l e a c h i n g . . . . . . . . . . . . . . . . . . . . O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . Output by dust ...................... O u t p u t by organic matter, removed by r u n - o f f . , T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL SUPPLIES-REMOVALS

t

t

t --

t t t

-t t t

0.3 t

3.0 t

3.5

54.1

5 t t t t 40.9 45.9

--t t t t 6.9 6.9

--t t t t

+3.1

-3.4

-14.3

68.4 68.4

270

6.11.3.6. Arable farming o f a tropical and sub-tropical nature, fruit and horticulture included This system can be divided into two subsystems. -- Plantation system on 80% of the total agricultural surface -- Small farm system on 20% of the total agricultural surface. Classification: Intensive arable. Reference: Husz-11; Tropical and subtropical arable farming, small farm system, Table 97. Intensive arable. Reference: Husz-12; Tropical and subtropical arable farming, plantation system, Table 98. Location: All over the continent, as far as ecological and topographical conditions and the traffic situation make it possible. The total surface involved is small (about 2%). It is distributed, with few exceptions along the coast of south and east Brazil, the Caribbean coasts and river oases in the arid zone of the Pacific coast. Climate: The climate is heterogeneous within the framework of tropical conditions and varies from a humid-warm equatorial to a sub-tropical desert climate (with irrigation). However, high temperatures of more than 25°C always last for at least 6 months, and mean temperatures do n o t fall below 14°C. Most of the time, rainfall periods and dry periods can be clearly distinguished. Mean precipitation, 156.3 cm; mean potential evapotranspiration, 203.4 cm; mean actual evapotranspiration, 146.9 cm. Soil: As a result of the widespread occurrence of this ecosystem, the softs are also very heterogeneous. However, in general, there are fertile well situated soils, under a mixture of arable farming and plantation culture. These soils are mainly on younger deposits of terraced landscapes (Riverside soils or colluvial soils) and flat-conical deposits from river systems: Eutric Fluvisols, Eutric Regosols, Ochric, Humic or Calcic Gleysols, Saline Vertisols, Eutric Planasols, Phaeozems. The oldest geological formations in southeast Brazil consist of acid crystallines (granite, gneiss, quartzite) encysted by red sandstone. They form acid, less fertile red soils (Ferric Luvisols, Humic Cambisols, or Acrisols). However, under the influence of spurs of the central Brazilian mountains (basic crystalline), weakly acid to neutral soils could be developed (Rhodic Ferrasols, Humic Ferrasols). In the neighbourhood of the coast, marine deposits also form soil (Xanthic Ferrasols and Orthic Acrisols). Mean productivity index, Qs, 0.512 (0.9 on irrigated soils). Use: The plantations cover a b o u t 80% of the agricultural area, the small farms occupy a b o u t 20%; livestock is almost absent. Productivity and nutrient balance: The plantations are very well fertilized, b u t the small farms, noticing the high yields on the plantations, also use more fertilizers than usual on such small farms in South America. The mean shoot index is 0.453 (0.56 on irrigated soils). The mean yield is 11 360 kg ha-' above-ground dry matter, and with irrigation 19 960 kg ha-'. For optimal

271

T A B L E 97 S y s t e m t y p e : Intensive arable

S u m m a r y of n u t r i e n t flows (units: kg h a -1 y - l )

T y p e of f a r m or e c o s y s t e m or t y p e of p a r t o f a f a r m or e c o s y s t e m , t e l no. H u s z - l l

Tropical and sub-tropical arable farming, small farm s y s t e m , S. A m e r i c a

Nutrient

N

P

K

t

90.9

t 18.2 -t 18.2

t 181.5 -t 181.5

34.1 -34.1 22.7 -90.9

6.8 -6.8 4.6 -18.2

68.0 -68.0 45.5 -181.5

0

0

0

Changes in a m o u n t of p l a n t c o m p o n e n t SUPPLIES:

REMOVALS:

29. 30t. 30r. 31. 3. 4. 18. 26. 27.

I n p u t b y seeds or seedlings . . . . . . . . . . . . . . . T r a n s f e r b y n e t u p t a k e f r o m soil . . . . . . . . . . . T r a n s f e r b y n e t u p t a k e f r o m soil . . . . . . . . . . . I n p u t by u p t a k e f r o m a t m o s p h e r e . . . . . . . . . . TOTAL

90.9 -t

T r a n s f e r b y c o n s u m p t i o n o f h a r v e s t e d crops . . . T r a n s f e r b y grazing o f forage . . . . . . . . . . . . . O u t p u t by p r i m a r y p r o d u c t s . . . . . . . . . . . . . . T r a n s f e r b y p l a n t p r o d u c t i o n r e m a i n i n g on field . T r a n s f e r b y seed for s o w i n g . . . . . . . . . . . . . . TOTAL SUPPLIES-REMOVALS

Changes in a m o u n t o f animal c o m p o n e n t SUPPLIES:

REMOVALS:

1. 2. 3. 4.

I n p u t b y feed for livestock . . . . . . . . . . . . . . . I n p u t b y litter used indoors . . . . . . . . . . . . . . T r a n s f e r b y c o n s u m p t i o n o f h a r v e s t e d crops T r a n s f e r b y grazing o f forage . . . . . . . . . . . . . TOTAL

5. 6.

O u t p u t by animal p r o d u c t s . . . . . . . . . . . . . . . O u t p u t b y losses f r o m m a n u r e to air, b e f o r e appncation . . . . . . . . . . . . . . . . . . . . . . . . . . . Output by manure . . . . . . . . . . . . . . . . . . . . T r a n s f e r by application o f m a n u r e a n d ] o r w a s t e . T r a n s f e r by droppings on g r a z e d areas . . . . . . . TOTAL

7. 8. 9.

. . .

SUPPLIES-REMOVALS Changes in a m o u n t o f total soil c o m p o n e n t SUPPLIES:

8. 9. 10. 11. 12. 13. 14. 15. 26. 27.

T r a n s f e r by application o f m a n u r e a n d / o r waste . T r a n s f e r by droppings on grazed areas . . . I n p u t b y application o f m a n u r e . . . . . . . . . . . . I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . I n p u t b y N-fixation . . . . . . . . . . . . . . . . . . . . I n p u t b y application o f litter, sludge a n d w a s t e . I n p u t b y irrigation and flooding . . . . . . . . . . . I n p u t b y dry and w e t deposition . . . . . . . . . . . T r a n s f e r b y p l a n t p r o d u c t s r e m a i n i n g o n field • . T r a n s f e r b y seed for sowingTOTAL ........ ' .....

R E M O V A L S : 19. 20. 21. 22. 23. 28. 30.

O u t p u t b y denitrification . . . . . . . . . . . . . . . . O u t p u t b y volatilization o f a m m o n i a . . . . . . . . O u t p u t by leaching . . . . . . . . . . . . . . . . . . . . O u t p u t by r u n - o f f o f available n u t r i e n t s . . . . . . O u t p u t by dust . . . . . . . . . . . . . . . . . . . . . . O u t p u t b y organic m a t t e r , r e m o v e d b y r u n - o f f . . T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL SUPPLIES-REMOVALS

34.1 . . 12.5 30.0

. t t t

12.0 22.7 11--1.3

6.8 . . 2.5 8.0 --

.

t t t

68.0 . 25.0 58.0 -t t t

4.6

45.5

21.9

196.5

--0

--10

t 20 5 t

t

t

t

t

t

t 90.9 115.9

t 18.2 18.2

t 181.5 191.5

- 4.6

3.7

+ 5

272

TABLE 98 System type: Intensive arable

Summary of nutrient flows {units: kg ha -I y-1 )

Type of farm or ecosystem or type of part of a farm or ecosystem, ref. no. Husz-12

Tropical and sub-tropical arable farming, p l a n t a t i o n s y s t e m , S. A m e r i c a

Nutrient C h a n g e s in a m o u n t SUPPLIES:

29. 30t.

30r. 31. REMOVALS:

3. 4. 18. 26. 27.

N

P

K

-111 -111

-25.0 --25.0

-228 --228

t

t

t

84 27 -111

-18.7 6.3 -25.0

171 57 -228

of plant component Input by Transfer Transfer Input by

seeds or seedlings ............... b y n e t u p t a k e f r o m soil . . . . . . . . . . . b y n e t u p t a k e f r o m soil . . . . . . . . . . . uptake from atmosphere .......... TOTAL

Transfer by consumption of harvested crops . . . Transfer by grazing of forage ........ - ..... Output by primary products .............. Transfer by plant production remaining on field . Transfer by seed for sowing .............. TOTAL SUPPLIES-REMOVALS

0

0

0

C h a n g e s in a m o u n t o f a n i m a l c o m p o n e n t SUPPLIES:

1. 2. 3. 4.

REMOVALS:

5. 6. 7. 8. 9.

Input by Input by Transfer Transfer

feed for livestock ............... litter used indoors .............. by consumption of harvested crops by grazing of forage ............. TOTAL

. . .

Output by animal products ............... O u t p u t b y losses f r o m m a n u r e t o air, b e f o r e application ......................... Output by manure .................... Transfer by application of manure and/or waste . Transfer by droppings ongrazed areas ....... TOTAL

--

SUPPLIES-REMOVALS C h a n g e s in a m o u n t SUPPLIES:

REMOVALS:

o f t o t a l soil c o m p o n e n t

8, 9, 10. 11, 12. 13. 14. 15. 26. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer

by application of manure and/or waste . by droppings on grazed areas ....... application of manure ............ fertilizers .................... N-fixation .................... application of litter, sludge and waste . irrigation and flooding ........... dry and wet deposition ........... by plant products remaining on field . . by seed for sowing .............. TOTAL

19. 20. 21. 22. 23. 28. 30.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... Output by run-off of available nutrients ...... Output by dust .................. •. . . . Output by organic matter, removed by run-off . T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL SUPPLIES-REMOVALS

t

t --

t 94 t t 10 5 28 -137

t 15.7 -t 3.0 t 6.3 -25

t

-t 101 -t 40 5 57 -203

--0

20 5 .

t --

--35

t t

t t

t t

t

t

t

111 136

25 25

228 263

+ 1

0

-60

273

TABLE 98 (continued) S y s t e m t y p e : Intensive a r a b l e

Summary of n u t r i e n t flows (units: k g h a - I y - J )

Type of farm or ecosystem or type of part of a f a r m o r e c o s y s t e m , ref. n o . H u s z - 1 2

Tropical and sub-tropical arable farming, p l a n t a t i o n s y s t e m , S. A m e r i c a

Nutrient

N

P

K

C h a n g e s in a m o u n t o f available soil n u t r i e n t s SUPPLIES:

REMOVALS:

8a. 9a. 10a. 11. 12. 13a. 14. 15. 16. 17. 26a. 27.

Transfer Transfer Input by Input by Input by Input by Input by Input by Transfer Transfer Transfer Transfer

19. 20. 21. 22. 23. 24. 25. 30t.

Output by denitrification ................ Output by volatilization of ammonia ........ Output by leaching .................... O u t p u t b y r u n - o f f o f available n u t r i e n t s . . . . . . Output by dust ...................... T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n Transfer by net uptake by the plant ......... Transfer by net uptake by the plant ......... TOTAL

30r.

by application of manure and/or waste . b y d r o p p i n g s o n g r a z e d areas . . . . . . . application of manure ............ fertilizers . . . . . . . . . . . . . . . . . . . . N-fixation .................... a p p l i c a t i o n o f litter, sludge a n d w a s t e . irrigation and floodlng ........... dry and wet deposition ........... b y w e a t h e r i n g o f soil m i n e r a l f r a c t i o n . . b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n b y p l a n t p r o d u c t i o n r e m a i n i n g o n field . b y seed f o r s o w i n g . . . . . . . . . . . . . . TOTAL

--

--

60

pm+60 ---

--

pm

SUPPLIES-REMOVALS

+60

C h a n g e s in a m o u n t o f soil o r g a n i c m a t t e r SUPPLIES:

8 b . T r a n s f e r b y a p p l i c a t i o n a n d / o r Waste . . . . . . . . 9 b . T r a n s f e r b y d r o p p i n g s o n grazed a r e a s . . . . . . . Input by application of manure ............ 1 3 b . I n p u t b y a p p l i c a t i o n o f litter, sludge a n d w a s t e . 25. T r a n s f e r b y i m m o b i l i z a t i o n in soil o r g a n i c f r a c t i o n 2 6 b . T r a n s f e r b y p l a n t p r o d u c t s r e m a i n i n g o n field . . TOTAL 10b.

REMOVALS:

17. 28.

T r a n s f e r b y m i n e r a l i z a t i o n o f soil o r g a n i c f r a c t i o n Output by organic matter, removed by run-off.. TOTAL SUPPLIES-REMOVALS

C h a n g e s in a m o u n t o f soil m i n e r a l s SUPPLY: REMOVAL:

24. 16.

T r a n s f e r b y f i x a t i o n in soil m i n e r a l f r a c t i o n . . . . T r a n s f e r b y w e a t h e r i n g o f soil f r a c t i o n . . . . . . . SUPPLY-REMOVAL

---

60 -60

274

T A B L E 99 S y s t e m t y p e : Intensive m i x e d

S u m m a r y of n u t r i e n t flows (units: kg ha -1 y-~ )

T y p e o f f a r m or e c o s y s t e m or t y p e of part o f a f a r m or e c o s y s t e m , ref. no. Husz-13

Mixed s y s t e m , t e m p e r a t e zone, S. A m e r i c a 33% arable farming, 67% livestock f a r m i n g

Nutrient

N

P

K

t 21.5 -t 21.5

t 187 -t 187

95 29.2 10 -134

t 14.9 4.9 1.7 -21.5

1.0 132 40.1 14 -187

0

0

0

Changes in a m o u n t o f p l a n t c o m p o n e n t SUPPLIES:

REMOVALS:

29. 30t. 30r. 31.

I n p u t b y seeds or seedlings . . . . . . . . . . . . . . . T r a n s f e r by n e t u p t a k e f r o m soil . . . . . . . . . . . T r a n s f e r b y n e t u p t a k e f r o m soil . . . . . . . . . . . I n p u t by u p t a k e f r o m a t m o s p h e r e . . . . . . . . . . TOTAL

t34 1

3. 4. 18. 26. 27.

T r a n s f e r b y c o n s u m p t i o n o f h a r v e s t e d crops . . . T r a n s f e r b y grazing o f forage . . . . . . . . . . . . . Output by primary products . . . . . . . . . . . . . . T r a n s f e r by p l a n t p r o d u c t i o n r e m a i n i n g on field . T r a n s f e r by seed for sowing . . . . . . . . . . . . . . TOTAL

t

-t 134

SUPPLIES-REMOVALS Changes in a m o u n t of animal c o m p o n e n t SUPPLIES:

1. 2. 3. 4.

REMOVALS:

5. 6. 7. 8. 9.

I n p u t by feed for livestock . . . . . . . . . •. . . I n p u t by litter used indoors . .. . . . . . . T r a n s f e r by c o n s u m p t i o n o f harvested c r o p s . . . T r a n s f e r b y grazing o f forage . . . . . . . . . . . . . TOTAL

. .

.

. 1 95 96

. .

.

. .

.

. 0.1 14.9 15

. .

. 1 122 123

O u t p u t by a n i m a l p r o d u c t s . . . . . . . . . . . . . . . 10.5 1.6 3.5 O u t p u t by losses f r o m m a n u r e to air, b e f o r e application . . . . . . . . . . . . . . . . . . . . . . . . . . . . Output by manure . . . . . . . . . . . . . . . . . . . . . . . T r a n s f e r b y application o f m a n u r e a n d / o r w a s t e . 1 0.1 -T r a n s f e r b y droppings on grazed areas . . . . . . . 85 13.3 119 TOTAL 96 15 123 SUPPLIES-REMOVALS

0

0

1 84

0.1 13.3 t 6.4 -t t t 1.7 t 21.5

0

Changes in a m o u n t of total soil c o m p o n e n t SUPPLIES:

8. 9.

10. 11. 12. 13. 14. 15. 26. 27. R E M O V A L S : 19. 20. 21. 22. 23. 28. 30.

T r a n s f e r by application o f m a n u r e a n d / o r waste . T r a n s f e r by droppings on grazed areas . . . . . . . I n p u t b y application o f m a n u r e . . . . . . . . . . . . I n p u t b y fertilizers . . . . . . . . . . . . . . . . . . . . I n p u t b y N-fixation . . . . . . . . . . . . . . . . . . . . I n p u t b y application o f litter, sludge and waste . I n p u t b y irrigation and flooding . . . . . . . . . . . I n p u t b y d r y and w e t d e p o s i t i o n T r a n s f e r b y p l a n t p r o d u c t s r e m a i n i n g on field . . T r a n s f e r by seed for s o w i n g . . . . . . . . . . . . . . TOTAL

t 15 25 t t 20 10 t 155 4 15 2

----

0 119 t 49 -t t t 14 t 182

O u t p u t b y denitrification . . . . . . . . . . . . . . . . O u t p u t b y volatilization o f a m m o n i a . . . . . . . . O u t p u t by leaching . . . . . . . . . . . . . . . . . . . . O u t p u t by r u n - o f f o f available n u t r i e n t s . . . . . . O u t p u t by dust . . . . . . . . . . . . . . . . . . . . . . O u t p u t by organic m a t t e r , r e m o v e d b y r u n - o f f . , T r a n s f e r b y n e t u p t a k e f r o m soil b y p l a n t . . . . . TOTAL

---

t t t 134 155

t t t 21.5 21.5

6 t t t 187 193

SUPPLIES-REMOVALS

+ 0

0

-11

275 conditions (soil improvement and irrigation) a yield of 33 600 kg ha -1 seems possible. The main products are maize, rice, potatoes and sweet potatoes, sugar-cane, bananas, pineapple, coffee, cacao, pulses, tropical and sub-tropical fruits (mango, cherimoya, avocado) (Husz, 1968).

6.11.3.7. Arable farming in a temperate climate, with green fodder and meadows (intensive grasslands and dairy) Classification: Intensive mixed. Reference: Husz-13; Mixed system, temperate zone, S. America, 33% arable farming, 67% livestock farming, Table 99. Location: Eastern part of mid-Argentina from Rio Uruguay to Bahia Blanca (plain, pampa) and Uruguay and south Brazil (hill, pampa): from the east side of the Rio Uruguay to the Atlantic coast. Climate: Mean annual temperature: 14--19°C; mean annual range: 12°C; annual precipitation: 60--130 cm; mean precipitation: 93.4 cm; mean potential evapotranspiration: 148.9 cm; mean actual evapotranspiration: 91.9 cm. Soil: The pampas extend over a b o u t 500 000 km 2 and are mainly covered with quaternary deposits. They represent the present land surface and are soil-forming. The soils are loess-like silty loamy soils. Loam and clay loam occur only in basins or on river beds. The deposits are calcareous and rich in plagioclas, hornblende, pyroxenes and volcanic glass (influence of volcanic ash from the youngest geological era). The rather humid zone of the hill pampas in the north contains fine granular material. Phaeozems with an argillic B horizon have been formed, and when the texture is very fine, vertisols can be found. The argillic B horizon is absent in the western part, as it is more arid here and the texture of the basic material is coarser, so that sand dunes are sometimes formed. The Phaeozems without a B horizon can be found in combination with Rhegosols. In the lowlands mainly saltic gleys and pseudogleys occur (gleyic solontschaks). The salinization is more intensive in the eastern pampa, where the natural drainage of the soil is bad and where lakes have formed in flat places. In this area, Mollic Solonetz, Mollic Planosols and Mollic Gleysols can be found. In the south-east, softs with a hardened CaCO3-horizon are predominant, and in this area, where deposits (mostly o f aeolic origin) slightly cover this CaCO3-horizon, Phaeozems and Planosols have been formed; in the basins Solonetza. In eroded places, the CaCO3-horizon lies at the soil surface and is soil-forming; then rendzinas are developed. Soil quality index, Qs = 0.742. Use: With the exception of the plantations on the tropical and sub-tropical areas, these systems are the most intensively used ones. The yields are low and can be compared to those of Europe in the thirties. Pastures and arable land alternate as a result of a special renting system which requires lucerne to be sown at the end of a renting period of a few years. It can then be used as a pasture for 5--10 years, practically without any further application of fertilizers. Thereafter, the soil is ploughed again; maize, wheat, sunflowers and linseed are the main crops.

276 Productivity and nutrient balance: The climatic conditions favour symbiotic nitrogen fixation. For lucerne, it is estimated that from 50 to 650 kg of nitrogen ha -1 can be fixed annually. If 150 kg N ha -~ is taken as a mean and it is assumed that lucerne covers 25% of the pastures, the mean nitrogen fixation on grassland is 37.5 kg N ha -~. With 2/3 pastures and 1/3 arable land, the mean nitrogen fixation is 25 kg ha ~1. The systems appear to be in equilibrium with applications of 45 kg of fertilizer N ha -~ arable land (15 kg N ha -~ agricultural area). The shoot index Qv = 0.444. This is 10 100 kg shoot dry matter ha -~, or 12 250 kg ha -~ with soil improvement (FAO and UNESCO, 1967; Duckham and Masefield, 1970; Fried and Broeshart, 1967).

277

Chapter 7 G E N E R A L DISCUSSION

7.1. I N T R O D U C T I O N

At the start of the symposium Dr Geertsema expressed the hope that the discussions would shed more light on the possibilities of increased food production for human society without wastage of resources and energy, and without undue damage to the environment. It was also hoped that areas of well defined knowledge, matters of divided opinion, and needs for future research might be identified. In this chapter an attempt is made to assess the contribution of the symposium towards these problems. In an experimental excercise of this kind generalizations are inevitable and any tentative conclusions reached here should be carefully considered for specific systems, and reconsidered in the light of subsequent new knowledge. At the symposium, Kolenbrander presented an analysis of the relationship between farm inputs and product (consumable) o u t p u t which is an assessment of production efficiency. A modified approach is discussed in the section which follows, on nutrient balances, by Frissel and Kolenbrander, together with their conclusions regarding losses of nutrients. Floate, in the section on changes in pool sizes, has attempted to identify c o m m o n features among the set of systems, and to analyse, for those systems losing nutrients from the total soil pool, the source of that loss from the subsidiary pools within the soft. From this analysis he has attempted to draw conclusions regarding the state of soil organic matter, and the fate of applied fertilizers. The possible manipulation of systems through use of fertilizers is discussed and the section concludes with a review of the needs for further research. 7.2. T H E N U T R I E N T B A L A N C E S ; S U M M A R I Z I N G G R A P H S A N D T A B L E S

(Frissel and Kolenbrander) A summary of the inputs and consumable outputs is shown in Table 100. This table also contains a qualitative indication of the state of balance of the nutrients N, P and K. The symbols +, 0 or - indicate whether the system gains, is in balance or loses the nutrient. Details are shown in Figs. 42--52 and Tables 101 and 102. Both inputs vary over wide ranges, which made it necessary to use logarithmic scales. In the figures which relate consumable outputs, losses to the atmosphere and leaching losses to the farm inputs, lines are drawn with equal outputs or equal losses, both being expressed as a percentage of the farm input. Figures which show the consumable outputs versus the farm inputs also contain lines (the d o t t e d ones) with equal absolute losses (in kg nutrient ha- i y - 1 ). In fact, all values refer to a period of one year; this is n o t indicated in order to avoid overloading the figures.

I

.

J 0'J

0

[~ ~l

Z

alq~mnsuoa

;

N

Zo I

l~O~L

,. . n _,-Tu :

~

[~o&

s'InduT,aoq~. 0

"~'[OZ.II!'~JOJ'T

olq~mnsuoo

t

i

I

I

IZ

I

I

I

~

I Z

i

I

o

~

i

i

+

~

,~ ~

J

i

I

I

,

I

I

i

i

I

i

i

i

J

I

I

I

I

tZ

I +Z

t

t

I +

+

I ZZ

I Z

I

I

[

14-

I

~ ~

i

I

tZZ

14"

i i

I

t

I

I

I

~

I

I Z

~ ~

I

~ ~; ~: ,-~ ~o

'~

"~

I

I

I

r

I

I "~

I

l~O.T,

~u!-n=u- i~',.o~,

~

c~ c~ ~

~

~

~

~

c:>

~

~

~

~

~J

i

~ndu! ~aq~ 0

~OZl[l~lO~[

Ind~.no

olqemnsuo~

I

I

I

I

"~ ~

~

I

I

I

I

cn

I

I

oo

I

co..

I

~

I

I

I

I

~

le~Oj,

i

i

~-d

paaT t°+UORlOt~n~

I

I

I

i

i

I

I

i

I

J

,--d

I

I

r

I

i

I

t'~

I

I

I

i

I

J

I

I

I

I

"0

~ ~ ~

~

, ~ i

~,~

~

.-

__

+++

++

++++~

=, ~ o o o ~

"~ =, ~_ :~ ' ~ ' ~ ' ~ o ~ o o ~

'~ ~ ~ ~ ~,~= ~ ~

~ . . . . . .

~ o

0 ~

+

~

c~ o ,-, ~ ,-,, ~, ,..., o~, . .~, . . =.~ o ~ o.= o,.~ ~.~

zz~:zzzz~=~5=5=~z~

_

, ~= _

200

Jacquard-4 Jacquard-3 Noy-Meir + Harpaz-5 Jacquard-5 Henkens-3 Newbould + Floate-9 Thomas + Gilliam-5 Thomas + Gilliam-4 Jacquard-6 Noy-Meir + Harpaz-6 Yatazawa-4 Huszol2 Thomas + Gilliam-1 Yatazawa-2 Thomas + Gilliam-2 Yatazawa-1 Kolek-1 Husz-8 Henkens-4 Henkens-5 Yatazawa-6 Yatazawa-3 Henkens-6 Yatazawa-5 Jacquard-7

42 369

-

-

158

19 26

8

14 17 53 6

5

12 6 9 10 20 57 10 43

6 14 17

5 5 15 10 7 10 42 27 10 14 14 132 7 14 5 -

-

-

-

-

14 20.3

95 400 672 115 232 172 800 95 209 106 122 72 10 138 211 101 783 319 293 265 346 105 800

6 33 343 100 42 40 59 178 61 57 55.7 43 200

14 66.2

5 20

5

21 31 50 60 5

55 123 40 44 18 20 20 80 -

-

-

-

-

120 4.7 50 5 120 10 50

134 71 50 11 153 353 150 42 40 59 178 61 57 76.7 74 250 60 100 400 672 120 232 172 800 100 229 106 122 127 133 178 256 119 783 319 313 285 346 185 800 126 137 162 166 175 400

81 82 84 85 88 90 96 82 113

77 79 80

66

29.2 43.9 40 49

34.1 36 36

11

2.3

80

70 72

17 115 -

-

-

-

60 63

5.7

38 10.5

19 17.0 20 9.6 24 26 30

19 19.3 20 20.6 24 26 30 34.1 36 36 38 39.7 43.9 45.7 49 60 63 66 70 72 77 79 80 80 81 82 84 85 88 90 96 99 113 115 126 137 162 166 175 400 24 31.8 79.9 30 45.8 150

48 15.7 30 37.7 19 45 100

25 14 101 160

80

75 100

11

50 50 8 13 79 24 6.4

10.4

-

.

.

-

.

. -

-

-

-

.

5 56.1 50 8 .13.1 79 24.3 6.4

1 13.1

11 6.1 6.1 75 100 . 80 38 38 0.3 25.3 14 0.1 101.1 160 . 0.2 48.2 3 18.7 0.3 30.3 0.2 37.9 0.3 19.3 3.1 48.1 13.7 114 . . 87 87 1 25 18.1 49.9 0.2 81.1 1 31 0.2 50 150

0.3

0.1

5 5.1

1 2.7

.

.

.

10 18.7 15 12.1 10 21.9 18.9 . 22 25 11 22.7 31 15 70

12 14 16.8 13 10 28

11 9.5 11 4

4 4.3 7 4.7 5 5 8 6.8 7 5 5 6.5 .

47

200 200 . 400 42 207 800 . 143 101 65 62 37 74 189 . 142 89 I 206 189 I 106 ~800

. 59.3

80 100 58 149 46 49

-

-

.

4 45 4 14 4 44 34

.

75 3 50 3

.

47

2 4 4

13 12

169 5 28 14 5 4 -

-

-

-

-

-

-

-

.

5 5.5

. 169 147 117 220 194 110 800

147 146 69 76 41 118 223

400 76 45 50 210 800

59.3 47 200 200

13 92 100 58 2 153 50 49

-

5 53

59.3 34 16 16

5 2.3 8 20 6 2 16 68 6 25 23 43.6

29 107 58 193 154 145 480

70 171 20 70 22 131 50

18 18 64 30 117 32

M e a n i n g o f s y m b o l s u s e d i n t h i s c o l u m n ; +, s y s t e m g a i n s n u t r i e n t e l e m e n t ; 0 , s y s t e m is in s t e a d ' s t a t e w i t h r e s p e c t t o n u t r i e n t e l e m e n t ; - , s y s t e m l o o s e s n u t r i e n t e l e m e n t ; N, data not provided.

96 143 91 400 305 161 256 332 100 800

90 400 400 98 179 168 800 90 204 94 112 65

-

Damen-2

37.9

300 100 30 34 50 168 41 45.7

-

Henkeas-1 Kolek-2 Jacquard-1 Husz-4 Henkens-2 Newbould + Floate-8 Jacquard-2 Husz-ll Thomas + Gilliarn-3 Jacquard-8 Thomas + Gilliam-6 Husz-13 Husz-5 Huszo7

+

+ + + +

+

+

+ + + + 0 0 + + + +

+ 0 0 + 0 +

+ -

+ + N + + + 0 + + N + 0 + + + + + N + + + + + + +

+ N 0

+

+

+ N + ' + + +

N + + + + ~ + N + ! + 4-

}"

280

7.2.1. Nitrogen T h e o u t p u t s o f c o n s u m a b l e n i t r o g e n v e r s u s t h e f a r m i n p u t s f o r a r a b l e systems, livestock systems and mixed systems, are shown in Figs. 42, 43 and 44, r e s p e c t i v e l y . A s e x p l a i n e d in C h a p t e r 4, c o n s u m a b l e p r o d u c t s c o m p r i s e p r o d u c t s s u c h as g r a i n s , r o o t s , t u b e r s , l e a v e s (in t h e c a s e o f v e g e t a b l e s a n d t e a ) , consumable

farm

output,

kg N / h a

~00

e f f i c i e n c y 200

300 200-

arable systems ~

O0

100

66

bO°/~

/~ ~ 3 o 20

:

50

30

//

20

z

10

1

.3

I

i ....

5

I I

I

I

I

10

50

100

250

5 0 0 kg l o s s / h a

2 0 0, farm

5,0 0r . . . . .1 0 0 0 i n p u t , kg N / h a

,

10

2'0

'

, 5 0, . . . . 1. 0 0

Fig. 42. The output o f consumable nitrogen vs. the farm input of nitrogen of arable systems. Forestry systems are indicated with an arrow. The shapes o f the symbols indicate the authors, consistently used for Figs. 42--45 and 47--52. [] Newbould + Floate o Husz o Damen Thomas + Gilliam Noy-Meir + Harpaz v Henkens Yatazawa a Ulrich DWilliams Jacquard Kolek Closed symbols: system with a nitrogen fixation above 35 kg N ha -1 y - I . Open symbols: nitrogen fixation is below 35 kg N ha -~ y-1 or unknown. The full lines connect points with equal efficiencies (100 x output/input). The d o t t e d lines connect points with equal absolute losses (kg N ha -~ y - I ).

281 consumable farm output, kg N/ha 500200

200300

livestock systems

/

oo.

Y

100 66 5 0

~

/77

,o

3o

10

0.5

30 ~1o

20

/I

3

/

I

o

~'

1

io

(

.

)

/

/50

100

2o ' ~ b i ~ o

1

250

500kg

loss/ho

260 5oo10bo farm input,kgN/ha

Fig. 43. The o u t p u t of consumable nitrogen vs the farm input of nitrogen of livestock systems. F o r an explanation of the symbols and lines see Fig. 42.

hay, milk and meat, b u t n o t straw and plant residues remaining on the field. For forests, w o o d which is carried off is considered. The farm input includes fertilizers, manure and inputs via irrigation and rain, b u t also the input via biological nitrogen fixation. Systems in which biological nitrogen fixation exceeds 35 kg ha- ' y- ~ are indicated with closed symbols. Mineralization of the initial a m o u n t of soil organic matter is n o t considered as a farm input. Fig. 42 shows that the o u t p u t of all arable systems is between 30 and 100% of the input, the only exception with a considerably lower o u t p u t being the system Newbould and Floate-6 (Meathop Wood) which appears to have a very high nitrogen fixing capacity (100 kg N ha- ' y- 1 ~. Up to a farm input of 150 kg N ha- 1 y- ' , the o u t p u t efficiencies are often close to the 66% efficiency curve. For inputs above 150 kg N hay-~, the outputs are scattered around the 50% efficiency curve, indicating slightly lower efficiencies at higher farm inputs. Fig. 43 shows the same type of graph for the livestock systems. Scattering of data points is much wider than for arable systems. A b o u t half of the points are within the efficiency range of 10 to 30%. A few systems have a better efficiency (Husz-6, Jacquard-1 and -3). Eight systems have efficiencies

282

between 3 and 10% and one system reaches an efficiency of no more than 1%. This system, Damen-1, describes the livestock part of a Dutch farm in 1800. The low efficiency can be explained by the fact that the main task of that part of the farm was not food production, but production of manure which amounted to 35 kg N ha- ' y- ' The absolute nitrogen losses of livestock systems are much higher than those of arable systems. In three cases the losses are even higher than 500 kg N ha- 1 y- 1 (Jacqaurd-6, Henkens-3 and -4). The surprising fact that these systems have efficiencies similar to systems with much lower inputs, can partly be explained by the fact that the input is mainly in the form of feed (158 and 369 kg N ha- 1 y- 1 for systems Henkens-3 and-4, respectively). Fig. 44 shows the results of the mixed systems. As could be expected, the results are intermediate between those of arable and livestock systems; extreme values are missing. A remarkable exception is system Husz-4 with an efficiency of 200% (input 11 kg N ha- ' y- ' , o u t p u t 20.6 kg N ha- ~ y- ~ ). Underestimation of the biological nitrogen fixation (estimated at 5 kg N ha-~ y-1 ) or mineralization of soil organic matter can explain this high efficiency.

consumable farm output~ kg N/ha 500-

efficiency

200

100

I

300200-

m i x e d systems

/

o

I

/,"/

66 50 a/o ///

I

//}~'~.//f/'~ 3o ///~ / / 20

lOO

20

/

lo

7"

,/.,/

// o/ /

/i

0 " 5 t4

/ , /

"C "

I

- /

/!

! /i

Hi

"50

I J

I 1 J/', /' /i i/

/

/,~

I

y

100

I

ii i

l

250

,

I'', ', i

,

5 0 0 kg loss/ha

/

.... ~b

20 ' ' s b " i ~ o

200 Sdo' iO'oo farm input, kgN/ha

Fig. 4 4 . The o u t p u t o f c o n s u m a b l e n i t r o g e n vs t h e f a r m i n p u t o f n i t r o g e n o f m i x e d syst e m s . F o r a n e x p l a n a t i o n o f t h e s y m b o l s a n d lines see Fig. 4 2 .

283

nitrogen leached kg N/ha leaching 200

100

100

66 50

30

20

10°lo

o,,

30-

,

5 ' ' ' lb

r 20

'

'Sb'

' '1~

' 260

3

~00'

' 10100

form input kg N/ha Fig. 45. The leaching o f nitrogen vs the farm i n p u t o f nitrogen. The full lines connect

points with equal leaching percentages (100 x leaching/farm input). Leaching values below 1 kg N h a - ' y - ' are grouped near the abscissa and indicated with < 1. The shapes

of the symbols indicate the authors; see also Fig. 42. Closed symbols: nitrogen fixation above 35 kg N ha-' y - ' . Open symbols: nitrogen fixation below 35 kg N ha-' y-' or unknown.

Nitrogen leaching data are shown in Fig. 45. They range from 1 to 100% of the farm input and rise to 90 kg N ha- 1 y- ~. Highest values are reported for the systems Thomas and Gilliam-5, Kolek-1 and Yatazawa-3 and -6 (products: cotton, mixed farming products, vegetables and tea, respectively). From a few systems, reported leaching losses are below 1 kg N ha- ~ y - ' . For some other systems no leaching data are given. These are all grouped near the abscissa of Fig. 45 and indicated with < 1 . A careful study of the original data, on which Fig. 45 is based, shows that the leaching data of Jacquard (symbol ~ ) are rather rough estimates and probably are less reliable than the other leaching data for farm inputs below 200 kg N ha --~ y- 1. The data of the systems Henkens-3 and -4 (symbols v on the extreme right-hand side of Fig. 45) are difficult to compare with the other data because the share of imported feed proteins for cattle is so high. If the mentioned values are disregarded, it appears that leaching losses for farm inputs below 150 kg N ha -~ y-1 are scattered around the 10% leaching curve, while for inputs above 150 kg N ha- 1 y- 1, they are scattered around the 20% leaching curve. Biological nitrogen fixation does n o t seem to influence the leaching percentage. Although for a particular site the a m o u n t leached per ha is, from a pollution point of view, decisive, this need n o t be true if the food production is considered o n a world-wide scale. On the latter basis, the ratio kg N leached: hg N in consumable output is more important. These ratios are listed in Fig. 46. The extreme ratios belong to the extensive livestock systems. For inputs

284

ratio

N, leached N,consumable output

3tt3oo 20-

251t9•,

~5

o

18-

•

16 14 e 12 o 10

o

08

•

o ,p

o

ooO

•

04

o

o

02

o°ooo

~ T

o o '

'

';

oo

.... 1'o

oo '

~, o o

'

¢

o

0.6

oo °

o

• o

o

' ~;o'",';oo nitrogen f a r m input, k g N / h o

r s ; ' " i ; o

Fig. 46. The ratio of leached N: consumable output N vs the farm input o f nitrogen. Ratios derived from leaching values below 1 kg N ha-' y - ' are grouped near the abscissa and indicated with < 0.1. Circles: arable systems; diamonds: livestock systems. Closed symbols: nitrogen fixation above 35 kg N ha -1 y - I . Open symbols: nitrogen fixation below 35 kg N ha-' y - ' or unknown.

above 150 kg N ha- 1 y- 1, almost all ratios are between 0.3 and 0.7. The nitrogen fixation systems Williams-l, Damen-1 and Newbould + Floate-7 show much higher ratios than other systems with comparable farm inputs. There is no indication that systems with high farm inputs show systematically higher ratios than systems with low farm inputs. Even if the data points based on the data of Jacquard and Henkens-3 and -4 are n o t considered, Fig. 46 does not provide a different pattern. Nitrogen losses to the atmosphere are shown in Table 101 and Fig. 47. Table 101 shows the losses by volatilization of ammonia as well as those by denitrification. It should be noted that fewer data are available for this source of loss than for leaching and even when figures are available they are often best estimates only. Fig. 47 presents the combined effect of both processes. Open symbols indicate that volatilization of ammonia dominates, and closed symbols that denitrification dominates. For a number of systems no or very low losses to the atmosphere were reported. These systems are grouped near the abscissa and indicated with < 1. For most of the livestock systems, losses are between 20 and 66% and volatilization of ammonia dominates. For arable systems m o s t losses axe between 3 and 30% and denitrification dominates. The highest loss reported for volatilization of ammonia equals 98 kg N ha- 1 y- 1 (system Thomas + Gilliam-6), the highest value for denitrification equals 192 kg N ha- 1 (system Henkens-4), N 2 0 production

285

TABLE

101

Losses by denitrification

and volatilization

System

System input, exclusive N-fixation (kg ha -1 )

Noy-Meir + Harpaz-1 Husz-2 Husz-1 Damen-1 H u s z -3 Kolek-2 Williams Thomas + Gilliam-8 Husz-9 Thomas + Gilliam-7 Husz-6 Husz-10 Newbould + Floate-7 Henkens-1 Henkens-2 Newbould + Floate-8 Husz-ll Thomas + Gilliam-3 Thomas + GUliam-6 Husz-13 Husz-5 Damen-2 Henkens-3 Newbould + Floate-9 Thomas + Gilliam-5 Thomas + Gilliam-4 Yatazawa-4 Husz-12 Thomas + Gilliam-1 Yatazawa-2 Kolek-1 Thomas + Gilliam-2 Yatazawa-1 Husz-8 Henkens-4 Henkens-5 Yatazawa-6 Yatazawa-3 Henkens-6 Yatazawa-5

of ammonia

Input by N-fixation ( k g h a -~ )

5 3 2.5 23 3 66.2

5 2.5 2.2 80 3 4.7 65

-10 41 11 9.2 15 153 14 33 343 42 40 178 61 57 43 572 115 232 172 209 106 122 72 211 10 138 101 783 319 293 265 346 105

1 Denitrification (kg ha -1 )

Volatilization (kg ha -I )

----

5 2.3 2 46 3 10.42 43 -20 -4 5 12 14 17 14 20 -98 15 3 -55 18 ---20 --243 --15 80 ------

16 -9.1 --

-25 8 8 8 150 120 120 10 -----31 -5 --20 --55 44 123 40 18 --20 20 -80

1 5 1 ---49 51 --5 5 4 -20 169 -20 15 30 -15 30 47 15 70 2 192 71 30 30 71 20

From 23 systems no losses by denitrification or volatilization reported. Unaccounted l o s s e s l i v e s t o c k s y s t e m 3 4 . 5 k g N h a -~ . 3 Unaccounted losses livestock system 23 kg N ha -2 .

of ammonia

have been

286

to atmosphere,kg N/ha

IOSS

1000

loss to atmosphere 200

100 % 66

500

011 s y s t e m s

so

300

30

200

20

100-

1o

5O 30-

3

20-

52 32

1-

__

l . . . . . .

,%~

2NO NO

+ 03 --> NO2

+ 02

03 + h v -> 0+02 NO2 +O--~NO+O2 Net results: 203 -~ 302 (Crutzen and Ehhalt, 1977). ( 0 ( 1 D) is atomic oxygen in an electronically excited state, which is produced from ozone and radiation; ), ..< 310 nm). It has been estimated that a global increase in nitrous oxide production by 20% will decrease the total ozone by 4% (Crutzen, 1974) and this, in turn, would result in an 8% increase in skin cancer (Grobecker et al., 1975). With the data available at present it is difficult to make a rigorous assessment of the magnitude of the impact on the ozone layer of nitrous oxide produced from nitrogen fertilizers. The problem is, however, receiving considerable attention, and WMO has r e c o m m e n d e d further studies on the nitrogen cycle (WMO, 1976). Only by a better understanding of all the facets of the global nitrogen cycle can the importance of N2 O production from fertilizers be evaluated. N2 O also contributes to the "greenhouse e f f e c t " by reducing the escape of thermal heat to the outer atmosphere, and it has been estimated that a doubling of the N 2 0 concentration will result in an increase by 0.7°K in the global surface temperature (Wang et al., 1976). There is a lack of data on in situ rates of denitrification and on the proportion of N2 O v s N2 in the end p r o d u c t from all types of soil. It can be hoped that recently published results on the inhibition of nitrous oxide reduction by acetylene (Balderston et al., 1976; Yoshinari and Knowles, 1976) will lead to the development of new techniques for determining denitrification rates in natural environments. Sulphur is also lost from soil to atmosphere under anaerobic conditions through the reduction of sulphate to gaseous Hydrogen sulphide. Bloomfield (1969) reported that 20--40% of the sulphate added to two topsoils was released as hydrogen sulphide. Sulphur gases are also evolved from animal manure, b u t the total amounts seem to be small (Banwart and Bremner, 1975). On a global scale, the release of gaseous sulphur c o m p o u n d s is in the order of 7.5 kg S ha- ' y- 1 (Sim~m and Jansson, 1976a). Most of this does, however, originate from swamps and marshy areas and it seems as if decomposing terrestrial plant litter supplies only 0.1--0.3 kg S ha- 1 y- 1 (Granat et al., 1976). In addition, 0.1--0.3 kg S ha- 1 y- 1 is lost in the form of organic sulphur c o m p o u n d s from soils (Hitchcock, 1975). The release of or-

302

ganic volatile sulphur compounds from agricultural soils seems to be very small (Banwart and Bremner, 1976). It has been shown that gaseous SO2, H2 S, NO~ and NH3 can be used as sole sulphur and nitrogen sources for higher plants (Failer, 1972). 7.4.4. Vegetation--soil as sinks and sources o f air pollutants

The importance of vegetation and soil as a sink for atmospheric pollutants has been pointed o u t by several authors (e.g., Hill, 1971; Smith et al., 1973; Munn and Phillips, 1975; Ghiorse and Alexander, 1976). These sinks are important n o t only for cleaning the atmosphere, b u t also because many of the pollutants can be used as nutrients by plants and micro-organisms (e.g. SO2 and NH3 ). Sulphur dioxide enters plant leaves through the stomata and at low concentrations photosynthesis can be stimulated (Knabe, 1976). Higher concentrations, however, cause both acute and chronic injuries to the vegetation (op. cit.). From data presented by Hill (1971), it can be calculated that vegetation around SO2 -emitting smelters in Sudbury, Ontario, could remove ca. 1 kg S ha- 1 day- ~ over an area of 225 ha. Nitrogen dioxide (NO2) is emitted during combustion and cm~ reach high concentrations, as for example in the Californian South Coastal Basin. As NO2 is rapidly converted to nitrate in plant cells, it can be used as a nitrogen source and the uptake of NO2 by alfalfa in the Los Angeles area could average as much as 0.28 kg N ha- ' day- x {Hill, 1971). N o t only vegetation b u t also soils absorb pollutants/nutrients (e.g. Smith et al., 1973; Ghiorse and Alexander, 1976) such as NH3, SO2, NO2. The vegetation could in some instances also act as a source of air pollutants. Miller and McBride {1975) when reviewing the effects of air pollutants on forests, pointed o u t that photochemically reactive hydrocarbons are emitted by the worlds' forests in the order of 175 × 106 tons y- ' , whereas man emits only 27 × 106 tons. It should be noted that the processing of phosphate rock for fertilizer production liberates particulate fluorides that can reduce crop yields (Rich, 1975). 7.5. MANIPULATIONS (Frissel)

There are many opportunities for man to manipulate or control nutrient cycles in agricultural ecosystems as described in Chapter 3. Because the data presented here deal almost entirely with the three main elements used in fertilizers, discussion was centred on several aspects of the use of fertilizers. These included (a) where in the world should fertilizer best be applied? (b) are fertilizers more effective in crops or livestock systems? (c) h o w can fertilizer efficiency be improved? and (d) which of the three major elements should receive most attention?

303

7.5.1. Future application of fertilizers The discussion was limited to agro-technological possibilities; political aspects -- for instance, h o w such a planning should be realized -- were n o t discussed. It was considered that one key question is: where s h o u l d w e apply fertilizers in the future, in developed countries or in developing ones? The idea on which this question is based is that developing countries, with their agricultural production at a lower point on the "diminishing returns curve" than developed countries, may obtain a higher fertilizer efficiency than the developed countries. The answer to the question also depends, without doubt, on the goal which is strived for; social, economical or environmental arguments will probably provide different answers. Apart from that, the question is n o t quite clear; does developing refer to a certain climate or land use, or to the a m o u n t of mechanization available, or to the economic structure which must be available to transport and sell the products? Therefore it is better to re