|Sustainable Agriculture and the Environment in the Humid Tropics (BOSTID, 1993)|
|2. Sustainable Land Use Options|
Farming systems that combine animal and crop production vary across regions and agroecological zones. In Asia the animal components of small farming operations vary with cropping systems (McDowell and Hildebrand, 1980; Ruthenberg, 1971). In lowland rice farming areas, buffalo provide (1) traction for cultivating fields and (2) milk and meat that are consumed domestically or sold in markets. Cattle, fowl (mainly chickens and ducks), and swine are also commonly raised on these farms. Feeds include crop residues, weeds, peelings, tops of root crops, bagasse, hulls, and other agricultural by-products. In highland areas, swine, poultry, buffalo, and cattle are raised in combination with rice, maize, cassava, beans, and small grains. Livestock is less important on farms dominated by multistory gardens, which may occasionally include cattle, sheep, and goats. Feed is typically cut and carried from croplands. Livestock animals are also of some importance on tree crop farms where they either graze freely in pastures, are tethered to clean specific areas, or are fed with tree cuttings.
The cropping systems of tropical humid Africa are dominated by rice, yams, and plantains (McDowell and Hildebrand, 1980; Ruthenberg, 1971). Goats and poultry are the dominant animals. Sheep and swine are less abundant, but still common. Feeds include fallow land forage, crop residues, cull tubers, and vines. The small farms of Latin America typically include crop mixtures of beans, maize, and rice (McDowell and Hildebrand, 1980; Ruthenberg, 1971). Cattle are common and maintained for milk, meat, and draft. Swine and poultry are raised for food or for sale. Pastures, crop residues, and cut feeds support animal production.
The literature dealing with agropastoral systems is scarce due to the lack of directed research and development efforts. Much of it was contributed by farming systems research (for example, Harwood, 1979; McDowell and Hildebrand, 1980; Shaner et al., 1982). The variety of agropastoral systems and the complexity of mixtures and interactions have discouraged systematic research and development. As farm diversification, soil and pasture management, and crop nutrient management become increasingly important to sustainable land use, these closely integrated systems should receive greater attention. Presently, most knowledge of agropastoral systems in the humid tropics resides with the native populations that manage them.
Features and Benefits of Agropastoral Farms
The close interaction between crops and livestock is the most striking feature of agropastoral farms. The structure of agropastoral farming systems is defined by the mix of crop and animal components, the extent of each, use of on-farm resources, interactions among the components, flows of energy and nutrients, and the individual contribution of each component to farm productivity (Harwood, 1987).
For example, in humid areas of Asia, land characteristics are a major determinant of crop and livestock components (Garrity et al., 1978). Heavy rains and fine textured soils make the lowlands most suitable for rice and a few other crops. Swine are raised by shifting cultivators, but the interaction between the animals and crops is largely unstructured. On more permanent farms, swine are typically raised in close association with vegetables that are produced for market (Harwood, 1987). In the humid areas of Africa, pests and diseases severely restrict the distribution of ruminants and people (Jahnke, 1982).
Agropastoral farming systems are usually highly diverse (Harwood, 1987). In most, several crops are produced on the same land within a single growing season or period, as in relay cropping or rotation systems, or within the same space simultaneously, as in intercropping systems. Rotations and polycultures are effective in controlling pests, diseases, and weeds (Altieri, 1987; Kass, 1978). They can also make nutrient cycles more efficient, protect soils from erosion, and influence the composition of the biota in and on the soil (Grove et al., 1990). Mixed systems appear to enhance productivity and stability, which may account for their widespread appeal.
Other benefits accrue from agropastoral systems. In effect, the incorporation of livestock into farming systems adds another trophic level to the system. Animals can be fed plant residues, weeds, and fallows with little impact on crop productivity. This serves to turn otherwise unusable biomass into animal protein, especially in the case of ruminants. Animals recycle the nutrient content of plants, transforming them into manure and allowing a broader range of fertilization alternatives in managing farm nutrients. The need for animal feed also broadens the crop base to include species useful in conserving soil and water. Legumes are often planted to provide quality forage and serve to improve nitrogen content in soils.
Beyond their agroecological interactions with crops, animals serve other important roles in the farm economy. They produce income from meat, milk, and fiber. Livestock increase in value over time, and can be sold for cash in times of need or purchased when cash is available (McDowell and Hildebrand, 1980).
Incorporation of animals into cropping systems requires increases in management and labor inputs in contrast to crop farming. Farmers also need to gather and process large amounts of information. For example, decisions and actions must occur according to complex time schedules and the flow of labor and materials must be coordinated.
Requirements for Greater Sustainability
The high degree of sustainability of agropastoral systems is a consequence of the efficient use of on-farm resources. But these farms are not isolated from external influences. Markets must be available if the economic benefits of livestock are to be realized. Labor must be available to fulfill the additional demands of the mixed system. Knowledge must be preserved and communicated to assure that managerial skills are maintained. These farmers must be protected from policy distortions that cause them to alter their mixed systems in ways that decrease their sustainability (for example, incentives to exceed the animal carrying capacity of their resources).
If the agropastoral farming systems employed by small-scale farmers are to be improved and promoted within the humid tropics, institutional and policy changes are required. Research institutions must address the complexity of these systems and undertake studies to improve them. Project sponsors must recognize that such research is new and may require continuous and perhaps long-term support. Educational outreach programs will be needed to promote improvements. Because traditional extension programs rarely focus on integrated management or small farms, changes are also required in these institutions. Governments need to avoid policies that cause small-scale farmers to abandon their mixed systems, and they must formulate policies that encourage and reward the protection of natural resources and environmental quality. A greater understanding of the interactions between national policies and local incentives would help assure that appropriate policies are developed.