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Land. Human population pressure, poverty and infrastructure are, as in grazing systems, the most important fundamental driving forces affecting the environmental impact of mixed farming systems in the developing world. And in that respect, the mixed farming systems are entering a dynamic period of growth and change because they cover some of the countries with the highest birth rates in the world (e.g., Uganda, the Sahelian countries, Ethiopia, Nepal, Bangladesh). Human population pressure affects soil fertility. In many parts of Africa and in the mountainous areas of Asia and Latin America, farmers attempt to maintain soil nutrient balance with, at best, small inputs from outside. Poverty and poor infrastructure usually prevent them from buying commercial feed and fertilizer (Box 3.3). Nutrient balance depends, therefore, on the ratio between arable and non-arable land. This also varies widely according to the climatic conditions. For example, in West Africa, the ratio was about 10 to 40 hectares of dry season grazing and 3 to 10 hectares of wet season grazing to provide adequate nutrients for one hectare of millet cropland (Williams, et al., 1995).
However, with increasing population pressure more and more grazing land is converted into cropland, the crop/grazing land ratio narrows, and the nutrient flow into cropland decreases. For example, cropland has increased in the Machakos area of Kenya from 35 percent of the higher potential area in 1948 to 81 percent (English, et al., 1993). In Northern Mali, the rate of increase of the arable cropping area was the same as the 2.6 percent rate of annual population growth over the last twenty years (Powell, 1995). This trend can lead to increased competition for cropland and grazing on the open rangelands, which in turn, can lead to privatization of crop residues and rangelands. For example, the common property lands in India, have decreased since 1960 by 50 percent, so that in 1992 they constituted only 15 percent of the total area (Jodha, 1992). Population pressure also causes farmers to push cultivation out into more resource limited areas, causing soil erosion. Mabbutt (1980) reports, for example, that in Niger millet fields are appearing 100 km north of the recommended limit to cultivation, increasing the risk of crop failure and leaving soil exposed and at risk of erosion. Livestock are moved to the most marginal areas.
Unless nutrients are replenished from outside sources, soil fertility continues to decline as the ratio between crop and grazing land declines. This is typically the case of many mixed farming systems in the tropics. Reported losses range from about 15 kg N/ha/year in Mali, to more than 100 kg N/ha/year in the highlands of Ethiopia. Downward spirals of declining soil fertility, overgrazing, and increased erosion and losses in soil micro-flora and fauna are the result and will cause, ultimately, significant decreases in agricultural productivity and political stability. The Rwanda example clearly underscores the need for a balance between crop activities, animal inputs and human population pressure, to avoid the collapse of the farming systems, impoverishment and even civil war (Box 3.4).
In irrigated mixed farming, grazing is more likely to be contained within the system although the source of feed supply is likely to shift increasingly from non-arable. grazing to grazing of crop residues and the use of fallow land. Inorganic fertilizers are used to overcome soil nutrient deficiencies.
Box 3.3 Farmers balancing their systems.
GLOBALLY mixed farmers have a history of attempting to optimize manure use in an effort to maintain soil fertility. Such efforts, however, are dependent upon access to livestock, feed resources for livestock, and the ability to store and apply manure. The examples presented below detail how well such efforts work and the potential problems involved in attempting to balance soil nutrient levels.
In Nepal, farmers know livestock are essential for maintaining soil fertility. Quantities of 3 to 20 MT/ha of manure are applied, with irrigated fields receiving larger amounts. Yields of 1.6 and 1.3 MT/ha respectively for a crop of maize followed by wheat can be sustained with 21 MT/ha of manure application. In these areas total livestock densities range from 9.8 to 16.7 livestock units/ha of cultivated lands. Six livestock units are needed to provide sufficient farmyard manure for one year to grow one hectare of rice-maize-wheat. This quantity of manure is presently not available, due to partial collection and inefficient storage.
In Indonesia, upland farmers apply manure on vegetables, rice, maize and cassava. Inorganic fertilizer applications are low. Maize and cassava grown on valley bottoms show a negative N. P. and K balance. The average density of cattle in upland Java is 2 head/ha which yields 2.5 MT/ha per year of dry farmyard manure.
a typical subsistence farm would have a negative nitrogen
balance of about 50 kg nitrogen/ha and is about
self-sufficient in phosphorus. A move towards commercial
dairy production would increase the outflow. But with the
cash generated from the dairy cattle a nutrient balance
can be achieved through a combination of manure and
commercial fertilizer. Nutrient balance studies (Ransom et
al., 1993) demonstrate how farmers strategically use
commercial fertilizer on coffee and use manure on maize
fields to achieve a nutrient balanced system. On sampled
farms manure application ranged from 3,000 to 13,000
kg/ha/year. Commercial fertilizer use was not consistent
as manure was used alone in 5 out of 7 years.
The main feature of the irrigated areas has been the dramatic intensification of crop production as a result of the Green Revolution. With the introduction of improved "dwarf'' varieties, the quality and quantity of crop residues decreased, but cereal production and total farm income increased. This has decreased the amount of feed available for ruminants, but increased the supply of cereals available for intensive production. Moreover, rising incomes as a result of the Green Revolution increased demand for livestock products. The two trends together promoted the development of intensive industrial units which, combined with the high fertilizer use in the Green Revolution areas, has led to increasing concerns about nutrient loading in regions such as the Punjab in India. In addition there are environmental concerns from the crop sector about salinization of soils, increased erosion rates around irrigation areas and increased use of pesticides.
The Green Revolution has also had an effect upon the use of draught power, one of the other major links between crops and livestock. Off-farm employment increases labour costs and, if the time available to prepare land becomes shorter, tractorization becomes more important, decreasing the use of buffalo and cattle for traction. For example, in India the number of bullocks used for animal power has decreased from 85 million in 1960 to 60 million while, over the same period, the number of tractors increased from 30,000 to 1.4 million. Only about 30 percent of the total arable land in India is still cultivated by animal power (World Bank, 1995).
Cattle-people ratio in Rwanda (1960-1993)
Box 3.4 Mixed farming in Rwanda.
PRIOR TO the colonial period, Tutsi and Hutu, mayor ethnic groups of Rwanda, had a working relationship which balanced the nutrient flows in the farming system. This was accomplished by the Hutu herding Tutsi cattle in return for receiving excess male offspring, manure and milk. As a result the Hutu farmland maintained or increased in soil fertility.
In the 1940's human and animal populations started increasing, and land previously reserved for grazing was converted into cropping lands. For example, from 1948 to 1991, population density in the Gikongoro province increased from 100 people/km2 to 287 people/km2. Farm size became smaller and livestock forage was reduced. Livestock ownership from 1967 to 1993 decreased from 1 in 2 households owning cattle to 1 in 4. These changes resulted in a reduction in nutritional quality and access to food since fewer animal products, pulses or cereals were being produced and people were relying more on tubers.
led to continuous cultivation and increased vulnerability
to soil erosion; reduced pastures resulted in fewer
animals and less manure; and farmers were forced to try
buying manure. Over 40% of survey respondents cited lack
of manure as a major reason for declining soil fertility.
This combination of poverty, population pressure and
resource degradation fed to the eruption of one of the
worst civil wars in modern times. Livestock provided an
important and stabilizing component of the farming system
by maintaining soil nutrients. Their increasing absence
contributed to the destabilization of a previously
balanced system. While it is certainly not clear whether
this drama could have been avoided, one might assume from
this analysis that improved incentives and technologies
for small-holder development, including, for example the
introduction of high yielding small ruminants, could have
reduced the downward spiral in resource degradation.
Biodiversity, Increased pressure and intensification of livestock production can cause both positive and negative effects. When livestock are used to reduce dependence on chemical methods to control weeds and insect pests, biodiversity losses are reduced (Box 3.5). On the other hand, excessive grazing pressure on communal areas adjacent to mixed farms has a negative effect, causing losses in biodiversity. There are many documented examples of the effect of livestock grazing on plant and animal biodiversity, especially on open access grazing areas. Overgrazing leads to a change in the composition of plant species. Fewer perennial varieties survive but annuals, of less nutritive value as fodder, become more abundant. This can have a long term negative effect on the value of grazing land and may lead to soil erosion as well as loss of biodiversity. In addition, intensification of production, following increasing population pressure leads, especially in dairy production, to the replacement of local livestock breeds by a small number of exotic breeds. The significant increase in tractorization, especially in Asia, has had the same effect, because the hardy, strong dual purpose traction/dairy breeds have been replaced with specialized dairy breeds (Chapter 5).
Box 3.5 Livestock and reduced chemical dependence in agriculture.
PRODUCTION in South East Asia is practised both on
plantations and small-holder farms (2 to 4 hectares in
size). In both cases, weeds are controlled by spraying.
Rubber producers in Malaysia. and Indonesia spend
approximately US$ 150 million and US$ 38.8 million'
respectively' trying to control the weeds which compete
with rubber tree growth. Researchers in both countries
have found 60 to 70 percent of the weeds that grow under
rubber can be used to support profitable sheep
enterprises. Sheep provide much-needed cash to rubber
producing small-holders. Environmentally, by combining
sheep and rubber production, herbicide use is reduced by
18 to 38 percent. Furthermore, by using sheep in this
manner, fertilizer costs are also reduced.
Source: T. Ismail and C.D. Thai, 1990.
Policies have often limited the beneficial impact of crop-livestock integration and exacerbated its negative environmental effects. These policies have been instigate* in some countries by a desire to achieve self-sufficiency, especially in cereals, and in others by the desire to provide cheap food for urban areas. To achieve self-sufficiency, markets were protected and subsidies were provided on inputs such as fertilizer, feed, fuel, etc. in order to increase production. This created disincentives for the use of on-farm products such as crop-residues, animal draught power and manure and contributed to a decline in mixed farming, with subsequent negative effects on the environment. More specifically:
subsidizing fertilizers, common in the oil-producing countries such as Nigeria, and many of the North African and Middle Eastern countries, hindered the integration of crops and livestock because it reduced the need for organic fertilizer;
subsidizing mechanization and fuel, again common in the Middle East, North Africa and Asia, reduced the need for animal traction and, as mentioned before, made possible the expansion of arable farming into marginal areas;
subsidizing concentrate feed, common in the Middle East and, indirectly through differential import duties on feeds in the KU, leads to the excessive use of concentrate feeds (for example cassava chips in Europe, Box 4.2). It also reduces the need for mixed farming. Globally, it contributes to a "feed nutrient trade deficit" in the developing world; and
poor land tenure security, especially in the rainfed mixed farming systems of the developing world, has discouraged investment in long-term soil fertility improvements, such as the use of inorganic fertilizers and the use of green manure and leguminous fodder crops within the crop rotation.
The policy of providing cheap food to urban centres has at the same time discouraged intensification, in some cases to the detriment of agricultural production as a whole and livestock in particular:
imposing high import duties to protect domestic cereal production, has had the effect of extending cropping into marginal areas and upsetting the equilibrium between crops and livestock;
overvalued exchange rates in sub-Saharan Africa and Latin America have favoured imports of cheap food from the industrialized world, thus competing against local production and providing no incentives for local producers to intensify into mixed crop/livestock systems nor to practice soil conservation.
Response: Technology and policy options
A fundamental requirement to achieve environmental sustainability of the natural resource base is to accept change and flexibility in the respective production systems and overall landscape (Levin, 1995). Agriculture, and crop agriculture in particular, seeks to stabilize production and limit environmental change thereby reducing the flexibility of the eco-system. But any ecosystem which supports the production of food, can be enhanced by the integration of livestock as a mechanism to promote system flexibility. Mixed farming, with careful attention to the nutrient balance, is therefore probably the most environmentally desirable system, and should be the prime focus of agricultural planners and decision makers. The challenge will be to identify the technologies and policies, which generate the sustained and accelerated growth needed to satisfy the world's booming demand for meat and milk. This challenge will be enormous. Past global growth of the meat and milk output of the mixed system has remained behind the increase in global demand. Will the growth in demand levels continue to rise beyond the capacity of mixed farm systems to meet national demands and therefore result in an immediate transition to highly intensive industrial systems? This study argues that, for environmental reasons, it is important to promote mixed farming in order to satisfy, as far as possible, global demand for meat and milk.
The key enabling factor seems to be access to inputs and attractive markets, as illustrated by the Machakos case study in Kenya. Here, a dynamic market and access to inputs has led to a fully sustainable development of a resource poor area, in which the population had quintupled over the last six decades (Box 3.6). Use of livestock in such intensive situations includes a shift in species from cattle to sheep and/or goats. In such intensive situations, sheep and goats are kept where difficult access to markets and milk processing facilities make keeping cattle a less attractive option (Cleaver and Schreiber 1994). Integrated crop-livestock systems have an immense potential to contribute to the required growth in productivity in the highland areas of Latin America and the semi-arid areas and highlands of sub-Saharan Africa where the population density is already high.
In spite of all the advantages of mixed farming, current trends point to specialization in either crop or livestock production, whereby the rate of change in any particular situation will depend on existing infrastructure, relative price ratios between the different inputs and outputs, and economies of scale. The development path that has been followed in the developed world and east Asia confirms this trend.
Box 3.6 Positive effects of population pressure.
MACHAKOS case. Human pressure intensification can also
work positively. Tiffen et al., (1992) showed
clearly that despite a 500 percent population growth over
the last 60 years in the semiarid Machakos district in
Kenya, the natural resource base improved. The key factor
leading to this success was dynamic market development
making farming profitable, generating off-farm employment
and supplying the capital for investmens in soil and
water conservation. Horticulture and small-holder dairy
production are the main activities generating the cash
for resource conservation, such as terracing. The famine
predicted in the 1930's for the Machakos district never
Technology. In mixed farming systems, there are exciting opportunities for technological change. Applied research and extension are of critical importance if the environmentally friendly factors of the system are to be maintained, although McIntire et al., (1992) make the point that African farmers are well aware of the technologies involved. The challenge will be to convince farmers about the value of technology. In the nutrient deficient systems of the developing world, the emphasis should be on control of soil erosion and improving nutrient recycling. Some examples are:
Improvement of soil cover through the use of alternative crops for mulching, and introduction soil management techniques such as conservation tillage, bench terracing, strip cropping, contour farming, etc.;
Improvement of feed production and quality to reduce the pressure on grazing areas and improve internal nutrient transfers. Technologies to do so include:
introduction of fodder shrubs and trees to reduce soil erosion and improve soil fertility. Several mixed farming systems using fodder shrubs and trees have been developed. An example is the agroforestry system with three strata (grass, fodder shrubs, and tree crops, such as oil and coconut palms, cashew nuts, etc.) as successfully introduced in Indonesia (Devendra, 1994);
improvement in feed quality, for example through urea treatment of feeds, as reportedly successfully used now by more than 5 million farmers in China (Li Biagen, pers. com.) and through increased efforts in plant breeding to correct the grain bias of the green revolution "dwarf' varieties and raise nutrient quality of the crop residues; and
use of non-conventional feeds (sugarcane tops and sugar cane juice, fruit tree and bamboo leaves).
Reduction of nutrient losses from manure and improved efficiency of their application by:
promotion of stall feeding which doubles the effective availability of nitrogen and phosphorus; and
strategic supplementation for specific classes of animals (lactating animals) to improve the efficiency of limited amounts of available feed.
Increased production efficiency, and thereby farm income, resulting in improved purchasing power for soil improvement and conservation methods. They include:
within breed improvement;
where appropriate, changing to small ruminant production or to optimal combination of ruminant and non-ruminant species; and
strategic supplementation of lactating and growing animals.
Policy. Clearly, for optimal development of mixed farm systems, a more open market economy is needed. In an open market there should be reduced subsidies for feed, fertilizer and mechanization. Phasing out of subsidies will promote a closer integration of crop and livestock systems in many parts of the world. It will enhance the use of home grown feeds, organic fertilizer and animal traction. To capitalize on free market transitions, better extension, improved financial institutions, security of tenure and, above all, better infrastructure are required.
The greater reliance on market forces needs to be accompanied by policies which seek to provide, for the most densely populated areas, the highest priority for employment generation outside the sector. This can be accompanied by market development for intensive crop and livestock production, such as horticulture and, in livestock, in industrial pig and poultry and possibly small ruminant production. This will enable adequate flows of nutrients in to the system and a rebuilding of environmental sustainability.
For the less critical, but still densely populated areas, markets and infrastructure are still important. For those systems, closer crop-livestock integration will help to reduce eventual nutrient deficits, but markets will always be required to supply external inputs. Technology and market policies should encourage rotations that maintain soil fertility and find synergies between crop and livestock activities.
Mixed farming systems in the developed world: Nutrient surpluses
Response: Technology and policy options
The mixed farming systems of the developed world cover about 17 percent of the world's pasture land and half of its arable land. They contain about one-fifth of both the world's cattle and small ruminant population. These systems generally show a much slower growth than mixed farming systems in the developing world. In some countries, mixed farming is contracting, reflecting the combination of stabilized demand in the OECD countries and the decline in the former Soviet Union and Eastern Europe, because of restructuring following the transition to a market economy.
With increasing population pressure, growing incomes and improved infrastructure and market opportunities, more intensive forms of crop and livestock production, including integrated systems evolve. These integrated systems come into dis-equilibrium in several regions of the world as a consequence of large nutrient imports from. outside the region, causing an overloading of soil and water with pollutants. The environmental challenge in the industrial countries, and to a large extent also in the fast growing economies of east Asia, is thus to identify, before it is too late, the point where land and aquatic ecosystems become overloaded. This is better than trying to identify technologies and policies which mitigate the negative effects of nutrient overloads once they have occured. In other words, "prevention is better than cure".
A further environmental challenge is to maintain biodiversity and an aesthetic landscape in heavily populated and developed mixed farming areas. Although opportunities to conserve biodiversity will not be able to mimic exactly the diversity associated with mixed farming in less developed areas, it should be possible to achieve some level of conservation. The challenge is to put in place technologies and policies which encourage farmers to retain a mixed farming system instead of specializing in the production of one or two crops only.
In the developed world, the environmental effects of mixed farming systems may include a deterioration in land and water quality (through soil erosion and nutrient loading), and biodiversity loss, especially through habitat change.
Soil erosion in the temperate zones (for example in the United States and in Europe), with a loss rate of about 15 ton/ha/yr, is half that of the developing world. But even this lower erosion rate exceeds by far the average soil formation of about 1 ton/ha/yr. (Pimentel et al., 1995).
Soil fertility. Soils in north western Europe, (the Netherlands, Germany, Britanny in France) in the eastern and midwestern USA and in the fertile and densely populated, and increasingly affluent, areas of east and south Asia, often reveal a surplus of nutrients. There are also widespread areas of central and eastern Europe where, as a result of very large livestock production units, there is a serious surplus of soil nutrients. While the total area with surplus nutrients is probably still very small (less than one percent of global arable lands (Rabbinge, pers. com.), through runoff its effect on water quality is much more widespread. Often such areas are near ports and/or large urban areas so that the transport costs associated with imported fertilizers, and the subsequent sale of milk and meat, are low.
The excess nitrogen and phosphorus "leaks" through leaching or run-off in surface or groundwater, damage aquatic and land eco systems. In Pennsylvania about 40 percent of the soil samples taken from dairy-crop farms revealed excessive phosphorus and potassium levels. Soils are saturated and surplus nutrients leach into surface water, pollute the environment, in this case the Chesapeake Bay. A similar situation is found in Brittany, France where all eight counties report nitrate levels of more than 40 mg/litre whereas, in the 1980s, only one county reported levels this high (Jensen and de Wit, 1996).
Biodiversity. The intensification of mixed farming and the subsequent shift in production towards regional specialization puts pressure on plant and animal biodiversity. In addition, the move towards sown pastures coupled with high levels of organic and inorganic fertilizer use reduces the richness of flora and fauna. This problem can be exacerbated by the use of insecticides for the control of external parasites, especially in areas with high water tables.
Box 3.7 Feed imports and inorganic fertilizer create system imbalances.
THE Brittany region of France, farmers import at least 40
percent of their animal feed requirements from other
regions, with the result that, on average, 134 kg
nitrogen is available per hectare from manure. In
addition 93 kg is purchased in the form of inorganic
fertilizer, against a crop uptake of only 146 kg N/ha.
This results in an excess of about 80 kg N/ha, causing
high nitrate levels in drinking water, and eutrophication
of inland surface waters and marine ecosystems. Nitrate
concentration typically exceeds 40 mg per litre, compared
with 25 mg/l as a guide level in drinking water.
Eutrophication of marine ecosystems causes algae growth
creating problems for shellfish producers. In some parts
(Saint-Brieuc Bay), shellfish have been contaminated with
bacteria and sales have been banned (Rainelli, 1991).
Source: Jansen and de Wit, 1996.
Soil erosion is strongly influenced by grazing pressure and cropping intensity. Reynolds et al., (1995) reported how variable soil erosion can be observed under different grazing pressures. Soil loss on lands with a good grass ground over has been estimated at 1 ton per hectare, this increased dramatically on overgrazed pastures to a level of 53 tons per hectare. If grazing pressure is in balance with the forage resource being produced, livestock's interaction can encourage more stable land use practices. Pimental et al., (1995) discussed how, in the United States, in order to increase farm size, grass strips and shelter belts were removed, thus increasing the erosion rate. In the past, livestock provided a rationale for grass strips and shelter belts but, with the separation of crop and livestock systems in OECD countries, the rationale for using land resources in this way has weakened.
Nutrient surpluses are the main cause of deteriorating land and water quality. These surpluses come from a combination of inorganic and organic fertilizers. Inorganic fertilizer is used, in spite of the fact that the system could be balanced using the nutrients supplied by the manure produced within the farming system. For example, in Brittany, organic manure produced by intensive industrial and mixed farms of the region could provide adequate nutrients but substantial surpluses emerge because of the additional import of large quantities (between 35 and 100 kg N/ha per year) of inorganic fertilizers. Inorganic fertilizer is said to be necessary because of the ready availability of its nutrients and its easy transport but, as in pure intensive grazing systems (Box 2.13), lower inputs might be adequate and even more economical. The preparation of nutrient balances (inorganic and organic) on a regional basis is therefore a critical element in identifying land conservation and fertilizer policies.
Policies designed to protect domestic production of most animal products, especially beef and milk, against imports and a broad array of producer subsidies, especially on feed imports, have led to the wide use of feed concentrates and therefore to situations where nutrients are in surplus. Such situations occur most often on the many small-scale enterprises which tax advantages and quota systems usually favour and where regulations are more difficult to enforce. Smaller size enterprises tend to have more lenient standards and are able more easily to exploit loopholes in regulations designed to protect the environment. These intensive systems using concentrate feed demonstrate how policies designed for social objectives can misdirect technology development.
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