The Role of Livestock for Sustainability in Mixed Farming: Criteria and Scenario Studies Under Varying Resource Allocation J.B

Agriculture, Ecosystems and Environment 90 (2002) 139–153

The role of livestock for sustainability in mixed farming: criteria and scenario studies under varying resource allocation J.B. Schiere a, M.N.M. Ibrahim b,∗, H. van Keulen c a Animal Production Systems Group, Wageningen Institute of Animal Sciences (WIAS), Wageningen Agricultural University, P.O. Box 338, 6700 AH Wageningen, The Netherlands b Department of Animal Science, Faculty of Agriculture, University of Peradeniya, Peradeniya, Sri Lanka c Research Institute for Agrobiology and Soil Fertility (AB-DLO), P.O. Box 14, 6700 AA Wageningen, The Netherlands Received 8 November 1999; received in revised form 30 January 2001; accepted 30 January 2001

Abstract Cropping, when possible, tends to become more important than animal production because, in general, it can feed more people per area unit in terms of calories and protein. In such systems, the role of wasteland grazing as a source of energy for agriculture through animals for traction and dung is often taken over by the use of resources from fossil reserves. This changing role of animals in the sustainability of agriculture is addressed in this paper to discuss options and constraints for animal production in newly developing farming systems. Based on a brief literature review, this paper discusses how and in which way ruminant livestock has played or can continue to play a role in (newly developing forms of) sustainable agriculture. The role of livestock in different modes of agriculture ranging from expanded agriculture (EXPAGR), and high external inputs agriculture (HEIA) to low external inputs agriculture (LEIA), and new conservation agriculture (NCA) are elaborated. It is argued that even when fossil reserves based external inputs such as oil and fertilisers become more widely used, they should still be used with care to save money and finite resources as well as to avoid problems of waste disposal. However, in conditions with limited access to resources, it continues to be difficult to obtain inputs from fossil reserves. Under these conditions, the major options to increase system sustainability by reducing pollution problems and dependency on external resources are (a) to adjust ways and objectives of production systems to the access to resources, and (b) to achieve increased use and recycling of resources within the system itself. Definitions for sustainability are given and translated into four criteria, i.e. food production and degree of self-sufficiency in the short term based on energy, protein, clothing, shelter, etc.; food production and degree of self-sufficiency in the long term expressed in the form of soil organic matter (SOM) content; reduced dependence of external inputs (=nitrogen use); and aspects of resilience, stability and equity in crop–livestock systems. The results of scenario studies concerning use of grass and legume leys for livestock production illustrate options and trade-offs for different crop–livestock combinations in terms of these criteria for sustainability. © 2002 Elsevier Science B.V. All rights reserved.

Keywords: Crop–livestock systems; Sustainability; Food production; Resource ﬂuxes

1. Introduction

Traditionally, animals and particularly ruminants ∗ Corresponding author. Tel.: +94-8-387180; were an asset to society by converting biomass from fax: +94-8-388041. vast grazing areas into products useful for humans, E-mail address: [email protected] (M.N.M. Ibrahim). e.g. dung, draught, milk, meat and security. However,

0167-8809/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved. PII: S0167-8809(01)00176-1 140 J.B. Schiere et al. / Agriculture, Ecosystems and Environment 90 (2002) 139–153 growing human populations cause increased and Table 1 shifting demands for food and other products. This Approximate number of people fed per hectare of land in areas results in the conversion of natural forests and grazing where cropping is possible (adapted from Spedding, 1979) land into arable land for crop and fodder production, Protein Energy thus leading to quantitative and qualitative changes Crops in biomass availability for human food and livestock Maize (Zea mays) 5.2 10.4 feed (Winrock, 1978). Where cropping is possible, it Wheat (Triticum aestivum) 6.3 8.4 can feed more people in terms of calories and protein Rice (Oryza sativa) 7.0 14.0 than what is possible with animal production. This Potatoes (Solanum tuberosum) 9.5 16.5 is shown in Table 1 (Spedding, 1979) with data for Livestock specific conditions that reflect the general principle. Chicken meat 2.5 1.0 Lamb meat 1.0 1.0 However, there are soils and climates where cropping Beef 1.0 1.0 is not very successful or very risky such as on the Pork 1.4 2.0 wet peat soils in Western Europe, in high mountain Milk 3.0 2.5 ranges or in arid regions (Fig. 1). Apart from their inferior caloric output, compared to crops, animals are also associated with defor- Poelhekke, 1984; Hecht, 1993). In the present day, the estation and erosion (Durning and Brough, 1991). strong argument against keeping of livestock is that the However, historically, deforestation tended to start in requirement for cropland is increasing through expan- response to the requirement for timber for fuel and sion of grain-based beef, dairy and poultry production construction (Ponting, 1991). Forest was cultivated in the USA, Western Europe, in peri-urban dairies of with crops and grassland for food production through developing countries, and recently in the Pacific Rim shifting cultivation, permanent cropping or simply and China (Winrock, 1978). Combined with changing as a method of occupying land (Ruthenberg, 1980; human food patterns, this has increased the demand

Fig. 1. Carrying capacity in terms of human population based on crop and animal production in areas where cropping is possible (adapted from Spedding, 1979). J.B. Schiere et al. / Agriculture, Ecosystems and Environment 90 (2002) 139–153 141 for crop land relative to grazing land (Alexandratos, 2. Livestock and sustainability of 1988). As a result, even marginal grazing areas are agricultural systems converted into crop land and overgrazing of the re- maining areas becomes the rule rather than the excep- 2.1. Role of livestock tion (Jodha, 1986). Land scarcity starts to occur, even in pastoral areas. This upsets existing ethnic balances, Livestock, and particularly ruminants, traditionally and can result in animosity between pastoralists and graze on natural pasture, forest areas, roadsides, fal- arable farmers who peacefully co-existed to mutual low lands, crop re-growth or crop residues such as benefit in the past (Powell and Waters-Bayer, 1985; straws, brans, oilseeds, and other by-products. When Grijseels, 1988). abundant feed is available, livestock can be considered The use of external inputs can increase the carry- a form of wealth, power and security, a perception ing capacity of some range-land systems (Breman and based on the conversion of solar energy captured in De Wit, 1983). However, such external inputs are not biomass into products valuable for human society. available or not affordable to all farmers. Hence, over Therefore, not surprisingly, strong linguistic links exploitation (i.e. mining) of land without the use of between the words for cattle and capital exist in lan- external inputs tends to be the result (Van Der Pol, guages all over the world (Schiere, 1995). For exam- 1992). This threatens the sustainability of these sys- ple, the Spanish ‘ganado’ is related with ‘ganar’, and tems, which is defined here in simple terms as “the similar relations exist in African and Asian languages. capacity to continue production”. Too liberal use of Indeed, under conditions of abundant biomass, cattle external inputs, on the other hand, causes waste dis- were often a decisive factor in the survival (sustain- posal problems or increased political dependency on ability) of a system. However, ways and objectives of external supplies (De Haan et al., 1997; Schiere and keeping livestock are changing as a cause and result of van Keulen, 1999). changing access to feed (Crotty, 1980; Palthe, 1989; In general, animals are often considered to be the De Leeuw and Rey, 1995; Schiere, 1995; Ifar, 1996). cause for unsustainability in both high and low exter- Often, animal production is associated with problems nal input agricultural systems (HEIA and LEIA). In of unsustainability. This may be true in some cases, LEIA, animals are blamed for scavenging whatever is in others it is definitely not. left, and in HEIA, the role of animals as waste utilis- ers has been reverted to a role as polluters and con- 2.2. Benefits of livestock verters of prime resources. Rather than being an asset to sustainability, livestock keeping has become a lia- Livestock were components of systems with long bility (Durning and Brough, 1991; Kaasschieter et al., term sustainability. For example, the keeping of live- 1990; Rifkin, 1992). stock was essential for survival in divergent systems The objective of this paper is to show that livestock such as those of the pastoralists in Africa, and those can play a positive role in sustainable systems. The on peat soil pastures of the low countries and on paper reassesses the controversial role of animals in mountain ranges unsuitable for cropping. Animals sustainable agriculture based on scenario studies and have long been essential in sustaining crop yields in literature. Specific objectives are (1) to describe a set the infield–outfield systems of Western Europe and of historical conditions where livestock has been es- other parts of the world, where dung and draught sential for the sustainability of existing farming sys- from wasteland grazing (outfields) was used for crop tems, particularly in mixed crop–livestock systems, (2) cultivation on the infields around the homesteads to outline a classification of livestock farming systems (Chayanov, 1926; Willerding, 1980; Bieleman, 1987). that ranges from predominantly animal production via In a more intricate way, animals helped to sustain mixed crop–livestock systems to predominantly crops crop yields by increasing the rate of nutrient flows at different ratios of relative access to land, labour and in the mixed crop–livestock systems of the Norfolk capital and (3) to provide some definitions and cri- and the Flemish systems (Slicher van Bath, 1963), teria for sustainability that can be operationalised in or by allowing farmers to include crops that ei- scenario studies. ther fix atmospheric nitrogen, release immobilised 142 J.B. Schiere et al. / Agriculture, Ecosystems and Environment 90 (2002) 139–153 phosphorus, or enhance soil organic matter (SOM, 3.1. Matrix to classify crop–livestock systems Hoffland, 1991). Grazing by livestock usually follows rather than The vertical columns of the matrix reflect the precedes deforestation and/or cropping. In fact, ani- degree of mixing between animals and crops, from mals, such as the goat, are one of the last means of predominantly livestock, via mixed systems to pre- survival for large numbers of poor people on bare, ex- dominantly crops (Table 2). The horizontal rows hausted, and/or arid lands. However, in spite of the represent four major modes of agriculture that tend importance of animals for the poor classes of farmers, to succeed gathering and hunting. The modes of the advocates for continued animal production on ex- agriculture are explained as follows. hausted soils should acknowledge that livestock can tip • Expansion agriculture (EXPAGR), where land is the final balance in delicate ecosystems (Schiere and abundant, i.e. where shortage of land or local fer- Grasman, 1997). Interestingly, Jodha (1986) notices tility is overcome by migration or expansion into that in the Nepalese hills, the goat can even be an other regions (Ponting, 1991). indicator of unsustainability. • Low external input agriculture (LEIA), where short- The following section provides a conceptual age of land cannot be overcome by migration. Lack framework to indicate when and where livestock of access to external inputs (capital) implies that can play a beneficial role in enhancing system only increased use of labour and skills offers a way sustainability. out. This in turn implies modified practices, where demand is adjusted to resource availability (Schiere 3. Conceptual framework to address livestock and De Wit, 1993). If not managed properly this can and system sustainability result in mining of soils and/or collapse of systems (Van Der Pol, 1992; Schiere and Grasman, 1997). • High external input agriculture (HEIA), based on Age-old systems can become unsustainable under high fluxes of external resources such as in the green changing conditions, alternatives and different objec- revolution. Basically, in this mode, the demand for tives of production may be required for survival of the output determines use of inputs (Schiere and De existing population (Hayami and Ruttan, 1985; Van Wit, 1993). The use of external resources can reach Der Ploeg and Long, 1994; Schiere and De Wit, 1995). such high levels that the environment is affected In that context, shortages of food and feed biomass, or by emissions from the crop and/or animal produc- even threats to sustainability can be tackled by a va- tion systems, ultimately leading to waste/disposal riety of methods (Boserup, 1965; Ruthenberg, 1980; problems, and also over-dependence economically Palthe, 1989; Schiere, 1995) as follows: (Kaasschieter et al., 1990; Rerat and Kauchik, 1995; 1. expansion of cultivated land through migration or De Haan et al., 1997; De Wit et al., 1997; Schiere shortened fallow cycles; and van Keulen, 1999; Van Keulen et al., 1999). 2. adjustment of consumption patterns and/or popu- • New conservation agriculture (NCA), is a mode lation growth; of farming where production goals are matched as 3. increased recycling of scarce resources; close as possible to the resource base. This ap- 4. reliance on (liberal) use of external inputs; proach represents a mix between HEIA and LEIA, 5. a combination of (1), (2), (3) and/or (4). and may be the archetype reasoning behind ecological farming (Altieri, 1991; Kingwell and Pannell, Based on the above biophysical strategies, it is 1987; NRC, 1989; Van Keulen et al., 1999). possible to classify farming systems. The classification presented in Table 2 is based on a matrix in which population density, access to land and inputs 3.2. Options and constraints of mixed change relative to each other. In more common terms, crop–livestock systems the classification is based on the relative availability of the production factors land, labour and capital This paper focuses on the options and constraints (Schiere and De Wit, 1995). of increasing the sustainability of mixed systems by J.B. Schiere et al. / Agriculture, Ecosystems and Environment 90 (2002) 139–153 143 144 J.B. Schiere et al. / Agriculture, Ecosystems and Environment 90 (2002) 139–153 utilising the animal component. Table 2 addresses fertility/nutrient deposits and rain are depicted in the both pastoral and pure crop systems, but it also empha- central box of the top row. From there, the resources sises the mixed crop–livestock system. This was not flow to either a short term deposit on the right, rep- addressed in the classification of Durning and Brough resenting biomass in forests, roadsides and grazing (1991). The latter argue against pastoral systems areas, to long term stocks on the left representing with associated overgrazing and against specialised fossil reserves from which “industrial” inputs such systems with associated waste disposal problems. as “improved” seeds and fertilisers are also manufac- Unfortunately, they insufficiently explain and explore tured, or they flow directly to the crop system. The the advantages of the mixed crop–livestock systems livestock subsystem, on the right “feeds” mainly on in terms of opportunities for waste recycling and for short term biomass deposits. The crop sector “feeds” optimal use of resources available on and between directly on solar energy, inherent soil fertility, on long farms. The following section discusses the constraints term deposits and/or indirectly on short term reserves and options in the design of mixed crop–livestock sys- that provide power and nutrients through livestock. tems of the NCA mode. Importantly, mixing can oc- The crossed broken lines are included to indicate cur within and between farms and this implies a high that livestock can “feed” on inputs of fossil reser- degree of integration of functions rather than mere ves through medicines, steel tools, etc. Livestock can diversification, where livestock and crops exist side further obtain food from cropping in the form of crop by side without being related to a significant extent. residues, failed crops and fodder production from leys, i.e. cultivated fallow. Feed resources from the cropping sector in mixed systems play an important 4. Changing relations between crops role, since in NCA they replace waste land grazing and livestock from EXPAGR as a source of feed in NCA (Table 2). The boxes “losses” indicate that not all resources are The main relations between crops and livestock transformed into a form that is directly beneficial to in mixed systems are simply depicted in Fig. 2. Ex- human society (Fig. 2). ternal resources such as solar energy, inherent soil The relative importance of resource flows between crops and livestock changes as systems move from one row to another in the matrix, or even between columns (Table 2). This is illustrated with a qualitative discussion of the changes in resource flows when mixed crop–livestock systems move from EXPAGR to HEIA (Fig. 3A) and from HEIA to NCA (Fig. 3B). The thickness of the arrows in the diagrams indicates whether a flow increases or decreases relative to its original value. For example, the bold arrow from fossil resource deposits to crops in Fig. 3A indicates that this flow is more important in HEIA than in EXPAGR. Fig. 3A thus shows that the importance of energy and resource flows in biomass provided to livestock from grazing land tends to decline as access to fossil fuel increases. In other words, fertilisers and fossil fuel replace dung and animal draught when the system moves from EXPAGR to HEIA. This change is associated with increased losses from the crop systems, which initially may not pose a concern as resources are cheap and waste disposal is not immediately Fig. 2. A generalised diagram with resource flows in a mixed problematic. Another aspect of this change is that the crop–livestock system. crop and the livestock components, when restricted to J.B. Schiere et al. / Agriculture, Ecosystems and Environment 90 (2002) 139–153 145

Fig. 3. Influence of mode of agriculture on resource flows in mixed farming systems. (A) Resource flows when mixed systems move from EXPAGR to HEIA. (B) Resource flows when mixed systems move from HEIA to NCA. See Table 2 for definitions of EXPAGR, HEIA and NCA. specialised farms, become independent of each other even continues to decline. The major change is the under increasing (fossil reserve based) resource flows. reduced use of resources based on fossil fuel, due to A peculiar case is the flow of livestock feed from either high prices of these inputs and/or problems of crop by-products (i.e. bran from cereal grain and cake waste disposal. Use of crop residues for animal feed (residue after oil extraction) from oil seed crops). It and of dung and urine for cropping ideally increases tends to increase at the macro scale because crop- together with the on-farm use of crop by-products ping intensifies, leading to production of more crop (brans/oilseed cakes). This helps to keep nutrients and by-products (Kelley and Parthasarathy, 1994; Joshi income opportunities in the local system, while allow- et al., 1994). However, the on-farm availability of bran ing animal production on a basal diet of low qual- and cakes (i.e. crop by-products) is likely to decrease ity feeds. It is difficult to substantiate, but it may be particularly on small and resource poor farms due to assumed that labour requirements for enhanced and increasingly centralised grain/oilseed processing. more judicious resource recycling increase in such The case in Fig. 3B represents an idealised situation system (Chancellor, 1981; Boonman, 1993). Essen- where farming moves from HEIA to NCA. Biomass tial in the current analysis is the increased potential from grazing areas remains a minor source of feed or for use of leys when systems move to NCA. A ley is 146 J.B. Schiere et al. / Agriculture, Ecosystems and Environment 90 (2002) 139–153 defined here as a fallow with planted forages in the also clothing, shelter, etc. The part of FOOD PLUS form of alley cropping, catch crops or grass/legume that exceeds subsistence requirements, can be sold pastures (Janssen, 1991; Boonman, 1993). Ley crops or exchanged for other goods. may serve a variety of purposes. Tree or cover crops 2. Degree of self-sufficiency in the long term,ex- can reduce run-off and erosion, while providing fuel, pressed in terms of SOM content. This assumes timber, etc. (Kang and Reynolds, 1989). Catch crops that land quality in terms of chemical fertility and can prevent leaching of nutrients, and legumes can physical structure is related to SOM content. No save on external resources by fixing nitrogen from the generally accepted standards for organic matter air. Other crops such as certain legumes (Stylosanthes quantity and quality have been formulated (which, sp.), grasses (Andropogon sp.) or Cruciferae (mus- in view of the current discussion, would be practi- tard seed) stimulate mobilisation of phosphate reserves cally impossible), but for West Africa, Feller et al. from the soil (Hoffland, 1991). The principal role of (1991) have suggested threshold levels for SOM livestock in NCA is to convert biomass from leys, as a function of soil texture to maintain physical bunds, alleys and catch crops into economically valu- and chemical soil fertility. able products, and to increase flow rates of available 3. Minimum, though not necessarily zero, use of ex- nutrients (Bosma et al., 1994; Stangel, 1995; Aarts ternal inputs, here expressed in terms of nitrogen et al., 1999). These aspects of crop–livestock integra- use. The choice for nitrogen is debatable because tion for increased sustainability are discussed in the (atmospheric) nitrogen can be considered a renew- following section. able resource, whereas phosphorus or potassium availability depends on fossil (finite) supplies. In that sense, resources such as water or fossil energy might also be more appropriate, but nitrogen is used 5. Modelling for sustainability here since it is very essential for life and because the reasoning can easily be extended to other nutrients. Most definitions of sustainability commonly focus 4. Criteria derived from system dynamics: sustain- on compromises among conflicting interests (WCED, ability in the face of stress or shock. These aspects 1987; Francis et al., 1990; De Wit et al., 1995; Schiere cover concepts such as system resilience, stability and Grasman, 1997). and equity (Conway, 1986; Holling, 1973; Pannell New insights from the theory on complex systems and Bathgate, 1991; Morrison et al., 1986). Quan- show that such a definition is bound to be open to mul- tification of these concepts is not attempted, but tiple interpretations, and efforts at achieving an objec- their importance is discussed. tive standard are therefore unlikely or even impossible to succeed (De Wit et al., 1995). Conway and Barbier (1990) supplement the above definition by emphasis- 6. Scenario studies ing that sustainability needs to be maintained ‘in the face of stress or shock’. This specifically refers to as- 6.1. Methodology pects of system dynamics and the link with concepts from ecology. However, this aspect of sustainability 6.1.1. Modelling approaches needs translation into measurable criteria/parameters Several modelling approaches and software pack- for practical planning and farm design (Checkland, ages are available for feed allocation and simulation 1991). A set of four criteria are proposed as shown of livestock systems. A number of scenario studies below. Threshold values are likely to differ as a func- was carried out at the Department of Animal Produc- tion of the prevailing conditions in space and time. tion Systems of the Wageningen Agricultural Univer- 1. Degree of self-sufficiency in the short term (FOOD sity, The Netherlands by using different approaches, PLUS), expressed as the number of people fed from i.e. linear programming (LP) (Kater, 1989; Bos, 1991; a given area unit, specified in energy and protein Insiani, 1990) and a combination of spreadsheets and requirements. The affix PLUS indicates that agri- dBase (Kaasschieter et al., 1990). Linear programming culture provides not only calories and protein, but (resource maximisation matrix) was used in many of J.B. Schiere et al. / Agriculture, Ecosystems and Environment 90 (2002) 139–153 147 the above studies because it is specifically designed for resource allocation, and it provides a convenient platform for interdisciplinary discussion. Also LP can do resource allocation over time and space with no difficulty other than an expanded matrix size. Linear programming is often understood to give one solution rather than a range, but this issue was overcome by running the model several times. The studies aimed at exploring options and constraints, rather than predic- tions, for crop–livestock integration for more sustainable forms of agriculture.

6.1.2. Approaches to evaluate the FOOD PLUS criteria The following four approaches were taken. 1. The output of the farm system was maximised for FOOD PLUS at a set of predetermined crop/ley ratios ranging from 100% crop to 100% ley. This resulted in a series of points that formed a response curve as in Fig. 4, an approach also followed by Renkema (1972), Morrison et al. (1986), Kingwell and Pannell (1987) and Schiere et al. (1999). 2. Losses that are either inherent to the process or Fig. 4. The behaviour of farm systems consisting of a series of are the result of inappropriate management/design ratios of crops and ley with and without livestock in relation to criteria 1–3 (see text). In (a), the broken lines a1 and a2 were ignored, although they can be quantified and indicate that the curvature of line AB is variable, but that the incorporated in more detailed modelling. combination crops and livestock can achieve higher total FOOD 3. The scenarios for sustainable crop–livestock sys- PLUS than crops alone. FOOD PLUS is defined as the degree of tems were examined through sensitivity analysis, self-sufficiency for energy, protein, and clothing, shelter, etc. In based on realistic standard values, rather than on (b), SOMG and SOML are points at which the graminae/grass and legume ley lines intersect the X-axis, respectively (see text). data collected for a particular case that cannot be extrapolated to other contexts. 4. The model assumed that a completely vegetarian diet was possible at 100% crops and that a diet 6.2. Results and discussion consisting of only animal products was possible at 100% ley. This simplification allowed the ex- The results of the scenario studies are simplified and ploration theoretical extremes. Pastoral tribes in summarised in Fig. 4a–c, where the horizontal axis Africa are known to survive almost entirely on represents the percentage ley in the system. The ley animal produce, and vegetarians survive well with- can consist of either grass, legumes or a mix of the two. out any food from animal origin (Spedding, 1979; The vertical axis in Fig. 4a represents the number of Reader, 1988). people that can be fed (FOOD PLUS), based on energy Although several aspects need further research (e.g. and protein requirements. The vertical axis in Fig. 4b labour or draught requirements, the effect of livestock and c represent the SOM balance and the need for ex- on nutrient dynamics, or the use of livestock for secu- ternal nitrogen, respectively, simplified and assumed rity or savings, or even the effect of seasons or indi- to be linear following Kaasschieter et al. (1990). Fig. 5 visibility of production factors), the results provide a shows how the case of Fig. 4 is likely to develop over useful framework for further discussion and research. time, i.e. it suggests that the negative SOM balance 148 J.B. Schiere et al. / Agriculture, Ecosystems and Environment 90 (2002) 139–153

from animal produce are assumed to be 5 and 10 times as high as from crops. The results are discussed below in relation to practical observations from ﬁeld conditions.

6.2.1. FOOD PLUS Cropping alone at any given time for system se- lected for the present study provided more FOOD PLUS than animals on fallow grazing or ley (Fig. 4a). Thus, cropping supported a larger population in the short term than 100% ley (Fig. 4a: lines AB and AB). In this highly simplified reasoning, the line AB for crops without livestock in Fig. 4a declined linearly with an increasing proportion of ley in the Fig. 5. The production of FOOD PLUS over time (solid lines refer to crop production only, broken lines to mixed cropping systems). rotation, purely because humans are not assumed to The t0, t10 and tn denote short, medium and long term, respectively. eat grass. However, the point A is likely to become FOOD PLUS is defined as the degree of self-sufficiency for energy, lower over time as decreasing soil fertility associated protein, and clothing, shelter, etc. with lower SOM levels in the absence of fallow/ley, results in lower crop yields. This is a typical example of a trade-off between short and long term at the left-hand side of the X-axis in year ‘0’ trans- food security, i.e. between FOOD PLUS and SOM lates into lower FOOD PLUS over years to come. (Table 2). As the SOM balance becomes positive at Fig. 6 shows how farm income varied at different lev- increasing proportions of ley (Fig. 5), crop yields over els of subsistence needs and when the price of nutrients time are sustained. Eventually, the line AB is hy- pothesised to assume the curvilinear shape, implying that in the long term, the combination of crops and livestock can support more people than either of the components alone. Inclusion of livestock (milk, meat) products (Fig. 4a: line AB) allows in principle also to feed more people than crops alone (Fig. 4a: line AB). An- imals utilise crop by-products such as brans, broken grains, oil seed, cakes, stovers and straws (Sundstøl and Owen, 1984; Joshi et al., 1994), but they start to increasingly use fodder as the proportion of ley increases along the X-axis. The effect of inclusion of livestock in a crop system on FOOD PLUS, i.e. the distance between lines AB and AB, depends on as follows.

• The requirements of humans for (animal) protein. When these are high relative to the energy needs, Fig. 6. Effect of crop–livestock integration on-farm income if the system will even use food (grains) for animal surplus production above different levels of subsistence needs can feed to generate more animal protein, thus reducing be sold, and where FOOD PLUS from animals is sold at five times total FOOD PLUS (Kater, 1989). as much as those of crops. The dotted lines AB and A B refer • to crop production and crop–livestock systems, respectively (see The quality of the crop residues and ley. Total text). FOOD PLUS is defined as the degree of self-sufficiency for output of milk and meat from livestock is low energy, protein, and clothing, shelter, etc. when only straw and stovers with low digestible J.B. Schiere et al. / Agriculture, Ecosystems and Environment 90 (2002) 139–153 149

energy contents are available. In that situation, the sources, contrary to legume leys that are self-sufficient distance between lines AB and AB is small, ig- for nitrogen. noring the fact that animal draught can be essential for land preparation. Importantly, for the design 6.2.3. Resistance to shock of new mixed systems, the amount of digestible A system (Fig. 4) at the left-hand side of the X-axis nutrients in straws and stovers can be increased with high FOOD PLUS is presumably politically sta- through treatments, agronomic practices or choice ble in the short term. However, pure cropping systems of cultivar (Sundstøl and Owen, 1984; Singh and produce less than mixed systems if no nitrogen and Schiere, 1993; Joshi et al., 1994). Also, the quality SOM are added from outside sources. This implies of ley fodder can be influenced, for example, by less stability in the long term and/or stronger political the choice between use of legumes or grasses, by dependence, again a case of short versus long term. cutting regimes, or by season. Moreover, the use of leys and keeping animals is a • Careful adjustment of individual animal and plant form of diversification that act as a kind of buffer with subsystem output for maximum total system output likely positive effects on the resilience and stability of as discussed by Kidane (1984), Schiere and Gras- a system (Bosma et al., 1993; Bosman, 1995; Mace man (1997) and Schiere et al. (1999). Individual and Houston, 1989; Sansoucy, 1995; Thomas and animal output cannot be very high if crop residues Lascano, 1995). and grasses alone are the sole feed resource. In fact, output targets that exceed the carrying capacity of 6.2.4. Nutrient cycling the feed resource base will even result in reduced Systems that shift towards NCA in Fig. 3B show total system output (Kater, 1989). a tendency towards intensive nutrient cycling within the system. Since all resources tend to cycle within 6.2.2. SOM and N balances the system, a disturbance in one of the subsystems A major purpose of including a ley for higher sys- translates into disfunctioning elsewhere. Whereas tem sustainability is to increase SOM including soil HEIA lies in the supply of external resources, NCA nitrogen (Theron and Haylett, 1953; Feigin et al., lies in the internal circulation and mutual adjustment. 1975; Kaasschieter et al., 1990; Bosma et al., 1994; Indeed, integration of crop–livestock systems for max- Bationo et al., 1995). As shown above, inclusion of imum FOOD PLUS in NCA is based on interdepen- a ley implies a trade-off between FOOD PLUS in the dency, i.e. it requires intensive mutual adjustment as short term and long term, or in terms of this paper: discussed above. This is different in EXPAGR where between FOOD PLUS and SOM. The comparison livestock and crops are managed rather independently between FOOD PLUS and SOM becomes more inter- as a form of risk-spreading and/or economic reasons esting when considering the choice between a grass through diversification. In EXPAGR, therefore, the and a legume ley. In principle, a fertilised grass ley failure of one is compensated by the success of the provides more SOM than a legume ley, if only be- other, in the case of NCA, failure of one component cause a legume uses part of the absorbed solar energy can imply collapse of the system. for the fixation of atmospheric nitrogen (Penning de The height of the lines AB and AB above the Vries et al., 1989). The point where net loss/gain subsistence requirements of a given population in of SOM is zero, is the minimum ley area required Fig. 6 indirectly indicate income in the system. In for sustained FOOD PLUS. This point (the intersect that case, it is important to know that the price for of these lines on X-axis) is indicated in Fig. 4b by energy and especially protein originating from ani- SOMG for grass and SOML for legume leys. If stable mal produce can be a factor 5–10 higher than those or increased SOM levels are required for sustainable from plant sources (Crotty, 1980). Therefore, when agriculture, (position of) these points illustrate that the production of a system is expressed in monitory less land needs to be followed, i.e. that more peo- terms, it moves to the line AB, illustrating that live- ple are likely to be sustained with a fertilised grass stock helps to compensate the losses incurred with a than a legume ley. The negative trade-off of a grass ley (NRC, 1989), thus positively contributing to food ley is that nitrogen has to be applied from external security in the long term. 150 J.B. Schiere et al. / Agriculture, Ecosystems and Environment 90 (2002) 139–153

6.2.5. Equity demand patterns. Proper system design and judicious Integration of crops and livestock on-farm can use of external inputs can correct imbalances in a enhance equity, one of the criteria for sustainabil- system with appropriate management. Especially, ity proposed by Conway (1986). It can also affect in pastoral and specialised systems, livestock keep- the export of plant nutrients to the urban centres ing is associated with environmental degradation, by providing labour opportunity and income for the but livestock creates opportunities for sustainabil- country-side, as more added value remains on farm ity in mixed systems. When land is the limiting when crop by-products are fed on farm. Integration of factor, a major production objective is to maintain several forms of production is likely to reduce pollu- or increase land quality, e.g. by maintaining or in- tion problems, because waste from one subsystem can creasing SOM levels for assured food production in serve as a resource for another subsystem. Thus, the the long run, and to increase total production per waste/losses ﬂows can be reduced due to integration unit land. as indicated in Fig. 3B.

Acknowledgements 7. Conclusions Thanks are particularly due to the students and col- Changes in resource/demand patterns cause changes leagues Marinus Bos, Loes Kater, Yun Insiani and Gert in the behaviour of (livestock) production systems. Kaasschieter whose work was at the basis of this pa- This implies that livestock can be essential for the per. Thanks are also due to Ton van Schie for his help sustainability of one system in one context and detri- in editing and revising several drafts and in preparing mental for the same or another system in a context the figures. elsewhere with other resource flows. It is possible to identify contexts and systems where livestock can be useful for increased sustainability and the generalised claims that livestock are detrimental is not sup- References ported. Clearly, the complexity of decision making increases when more factors are involved, i.e. when Aarts, H.F.M., Habekotté, B., van Keulen, H., 1999. Nitrogen (N) management in the “De Marke” dairy farm system. Nutr. Cycl. more criteria for sustainability are used. It is a form Agroecosyst. 56, 231–240. of experimentation and data handling that is alien to Alexandratos, N. (Ed.), 1988. World Agriculture: Toward 2000. the traditional approaches in reductionist research that FAO, Belhaven Press, London, 338 pp. separates all factors to study only a few at a time. Altieri, M., 1991. How best can we use biodiversity in This paper breaks with such a tradition. The planning agro-ecosystems. Outlook Agric. 20 (1), 15–23. and design of sustainable farm systems is a process Bationo, A., Buerkert, A., Sedogo, M.P., Christian, B.C., Mokwunye, A.U., 1995. A critical review of crop-residue use that involves multiple criteria for system success and as soil amendment in the West African semi-arid tropics. In: sustainability in situations that change over time and Powell, J.M., Fernàndez-Rivera, S., Williams, T.O., Rénard, C. space. Conceptual models discussed allow identifica- (Eds.), Livestock and Sustainable Nutrient Cycling in Mixed tion and quantification of important issues, but they Farming Systems of Sub-Saharan Africa. Vol. II: Technical clearly generate as many questions as answers. De- Papers. ILCA, Addis Ababa, pp. 305–322. Bieleman, J., 1987. Boeren op het Drentse zand 1600–1910. pending on conditions in time and space, a decision Een nieuwe visie op de ‘oude’ landbouw. Ph.D. Thesis, can be taken that selects the best (or least destructive) Wageningen Agricultural University, Utrecht, The Netherlands, option. 834 pp. Reduced access to land leads to modified, if not Boonman, J.G., 1993. East-African Grasses and Fodders: Ecology lower biomass (=feed) availability. When expansion and Husbandry. Tasks for Vegetation Sciences, Vol. 29. Kluwer of the resource base such as prevalent in the EXPAGR Academic Publishers, Dordrecht, Boston, London, 343 pp. Bos, M., 1991. The role of livestock and ley in mixed farming, and HEIA mode of agriculture becomes difficult, with special reference to nitrogen and soil organic matter. M.Sc. sustained production of FOOD PLUS must originate Thesis, Department of Tropical Animal Production, Wageningen from savings in the system or from adjustment of Agricultural University, The Netherlands (unpublished). J.B. Schiere et al. / Agriculture, Ecosystems and Environment 90 (2002) 139–153 151

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