Integration of trees and livestock in tropical agriculture
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CTA. 1991. Integration of trees and livestock in tropical agriculture. Spore 32. CTA, Wageningen, The Netherlands.
Permanent link to this item: http://hdl.handle.net/10568/45465
Although trees and livestock are not closely-linked components of modem western agricultural systems, this was not always the case. Traditional 'woodpasture' systems were widespread in Europe and allowed production of meat, firewood and building...
Although trees and livestock are not closely-linked components of modem western agricultural systems, this was not always the case. Traditional 'woodpasture' systems were widespread in Europe and allowed production of meat, firewood and building timber from the same area of land. What are the benefits of such systems today in the Tropics? In recent years, increasing pressure on land in tropical countries has resulted in massive deforestation with consequent erosion and reduction in soil fertility as well as serious shortages of fuelwood. This has convinced many agricultural scientists that trees have a crucial role to play in tropical agriculture and that they should not be confined to intensive plantations but should instead be integrated with arable agriculture and livestock husbandry. Integration of livestock and trees makes excellent sense for farmers in tropical countries, both in terms of intensification of land use and economic security. Because animals provide traction and manure in addition to meat, milk and hides, their inclusion in the farming system actually increases crop production. They need not compete for land with crops, so long as adequate forage is available throughout the year. In addition to the advantages mentioned above leguminous trees, which fix nitrogen, can provide protein-rich leaves as supplements for ruminants and pigs, and nutritious browse during periods when other feeds are unavailable. (See CTA Activities, Spore 31 'Caribbean livestock: improving health and nutrition'). Farming systems that integrate trees with livestock In the semi-arid areas of Africa both pastoralists and farmers encourage the growth of acacia trees; the highly nutritious foliage and pods provide an important source of dry fodder for their animals. In the Sahel one species, Acacia albida, is particularly important since it produces green foliage throughout the dry season when other sources of forage are scarce. An abundant crop of nutritious pods is also produced at the end of the dry season, when the need for fodder is greatest, and a single tree will produce between 50 and 150kg of pods per year. Similarly, in the semi-arid highlands of the Haraghe region of Ethiopia a traditional agroforestry system based on A. albida has evolved. Estimates of the additional income resulting from growing the trees in the farmers' gelds suggest that the value of produce (cereal grain and stover, fuel-wood and fodder) increases in proportion with the cover of the tree canopy. At a planting rate of 20 trees per hectare, the additional value of the produce (compared with fields without trees) was equivalent to US$230 per hectare per year and the total value of the fodder produced was about $370 per hectare per year. To date, tree-planting in semi-arid areas has mainly been done in the context of fuelwood and erosion control programmes and the benefits to agriculture are poorly documented. Nevertheless, species suitable for semi-arid areas of the highlands of East Africa have been identified by the International Council for Research in Agroforestry (ICRAF) at Machakos in Kenya. They include Leucaena, Acacia albida, A. tortilis, Sesbania sesban, S. bispinosa, Prosopis juliflora and P. pallida. Not all of these have been tested in farmers' fields but recent experiments in a semi-arid region of India using leucaena in mixed sorghum and livestock smallholdings gave remarkable improvements in sorghum yields and provided a valuable source of fodder and firewood. Here, leucaena was planted in rows 6m apart with sorghum planted between. The trees were pollarded at 2m height immediately before planting the sorghum, and the leaves were fed with sorghum stover to cattle. The researchers found that the value of produce from the leucaena/sorghum combination was about one third greater than that from sorghum alone and that income from the forage accounted for about 20% of the total value. Another way in which trees and livestock can be integrated is by growing forage under tree plantations. This is widely practised in Goats browsing on leucaena the Pacific region, where both cattle and small ruminants are grazed under coconut plantations; in S.E. Asia, in rubber and coconut plantations; and, to a smaller extent, in West Africa in oil palm plantations. Grazing animals in plantations has a number of advantages for smallholder farmers. Under-utilized land and labour are made more productive and farm income is increased. With careful management, improvements in growth and yield of the tree crop can be achieved and considerable savings can be made in costs of herbicides to control ground-cover herbage. Because the market price of the produce from tree crops (particularly copra and coconut oil) fluctuates widely, inclusion of livestock in the system provides a buffer against falling prices. Since tree crops take a minimum of 6 to 7 years before coming into economic production, a combination of forage and food crops intercropped with young trees can help to offset the costs of establishing plantations. Finally, the cooler temperatures under tree plantations can provide a better microclimate for animal production than unshaded areas. Studies carried out in S.E. Asia and the Pacific illustrate the benefits of integrating livestock with coconut production. In southern India, the net return from smallholder coconut plantations was calculated as approximately US$350 per hectare per year, but when milk cattle were included net returns increased to $942 per year. Likewise, in the Philippines a recent comparison of the relative returns to coconut plantations alone and coconuts with beef cattle showed that inclusion of cattle more than doubles net returns, from $159 to $327 per farm per year. Inclusion of improved forages can often dramatically increase liveweight gains and profits from livestock in plantations. In the New Hebrides, planting guinea grass (Panicum maximum) and forage sorghum under coconut resulted in a ninefold increase in profits from livestock as compared with unimproved native pasture species. In much of humid S.E. Asia the creeping legumes calopo and puero (originally introduced to plantations as ground cover to control weeds) provide nutritious fodder for animals and there is considerable scope for improving pastures under plantations with these and other forage legumes. Alley cropping The third example of integrating trees with agriculture is a more recent development which has not yet been widely adopted by farmers in the Tropics. However, many agriculturalists think alley cropping has immense potential for stabilizing and improving smallholder farming. Traditional agriculture in the Tropics relies on the bush fallow system of shifting cultivation to restore soil fertility. Following forest clearance and cultivation, the litter from the dense growth of shrubs which develops on fallow land restores soil organic matter, the key to maintaining fertility. This system has maintained crop yields and soil fertility on the fragile soils of the humid tropics for millennia, but more recently growing populations have led to increasing demand for food, resulting in shortened fallow periods. The consequences for soil fertility and crop yields have been disastrous. Within living memory, average crop yields in parts of humid West Africa have almost halved, and in some areas cultivated land has even been abandoned as a result. Scientists from the International Institute for Tropical Agriculture (IITA), at Ibadan in Nigeria, have tested a system to replace shifting cultivation that would allow continuous cropping without the resulting loss in soil fertility. Alley cropping consists of hedges of fast-growing shrubs interplanted with food crops. Using nitrogen-fixing leguminous shrubs such as leucaena or gliricidia, crop yields have been maintained at reasonable levels over several years, without the need for a fallow period. The system has several advantages. The shrubs provide green manure or mulch for companion crops, a source of stakes and firewood and, most importantly, biologically-fixed nitrogen to maintain and enhance soil fertility. Additionally, alleys planted along the contours on sloping ground can help to prevent soil erosion. Researchers from the International Livestock Centre for Africa (ILCA), who also worked at Ibadan, realized that this system might also provide a means of improving productivity of sheep and goats in humid Africa, where forest sheep and dwarf goats are traditionally raised. Because they are fed only on kitchen refuse and agricultural by-products, such as cassava leaves, their productivity is low and surplus meat is rarely produced. Demand for fresh meat in the towns of West Africa is increasingly met largely by expensive beef. If the productivity of local small ruminants could be raised, a large and easily accessible market for meat would be available to farmers. Problems and outlook for integrating livestock and trees The leaves of both leucaena and gliricidia are highly nutritious for small ruminants and are produced throughout the dry season in humid regions, a period when other forages are scarce. Trials in which grass supplemented with varying quantities of leucaena or gliricidia leaves was fed to West African dwarf sheep show that inclusion in the diet of only 800 grammes of leaves per day increased liveweight gain by 30% and survival of the young by 26%. After some initial reluctance, many local farmers have adopted the idea of feeding browse from alleys to their animals, so that in only five years over 60 farmers in the Ibadan region established new alley farms. One of the advantages of the system is that it allows farmers freedom of choice as to how they use browse, either as fertilizer for crops or feed for animals, according to their own needs and the relative price of meat versus food crops. Following the initial success of alley farming in the Ibadan region, ILCA has started a network throughout West Africa to promote integration of trees and livestock. The examples that have been described suggest that integration of livestock husbandry with trees could provide major benefits for farmers in ACP countries. But it would be wrong to assume that there are no problems to be overcome and that the future of agroforestry in the Tropics is guaranteed. One general problem, particularly in Africa, is that of communal land tenure. Where farmers do not have individual tenure rights, the incentive to plant trees, which have long-term production cycles, is very low. This is probably one of the reasons for the relatively slow uptake of alley farming in West Africa, where much land is held communally or by tenant farmers. Likewise, in humid areas where the natural regrowth is dense bush, there may be considerable reluctance by farmers to plant shrubs or trees on land which they have recently spent much effort on clearing for food crops. Furthermore, in densely populated areas, such as the highlands of East Africa, land is already intensively used and any new management system needs careful on-farm testing to ensure that the benefits outweigh the disadvantages in actual practice. Also, where a completely new system such as alley farming is introduced, farmers may lack the management skills in both agroforestry and animal husbandry which are necessary to maintain productivity. Apart from such social and economic constraints, technical problems may also restrict opportunities for integrating livestock with trees. In many tropical areas animal diseases are a major problem. Much of the humid forest region of Africa is infested with tsetse fly, and only trypanosomiasis-resistant animals can be raised. In the same area, the disease PPR ('Peste des petite ruminants') causes serious weight loss and abortion in sheep and goats and the advantages of alley farming can only be fully exploited if animals are regularly vaccinated against the disease. When livestock are grazed in tree plantations, competition for nutrients and water between the trees and the pasture may result in poor establishment of one or other of the two components. There is often initially a considerable problem in preventing animals damaging young trees and then, as the tree canopy develops, in preventing overgrazing and maintaining a healthy sward in the heavily-shaded conditions. In this situation, careful regulation of stocking rates is essential and requires considerable livestock management skills. In the drier areas of the Tropics, competition between trees and pasture for limited soil moisture can also be a problem. There is also a pressing need to identify tree species that can grow well under the poor and erratic rainfall conditions encountered in such areas. Despite all these problems, the integration of livestock farming with trees in the Tropics is likely to expand for a variety of reasons. In many areas, deforestation has resulted in critical shortages of fuel and timber as well as serious soil erosion. While the conventional response of establishing fuel-wood plantations can provide a partial solution, shortage of land for food crops places a limit on the area that can be planted. Integration of trees in farmland simultaneously provides fuel and helps to control erosion. Including an animal component in the system not only provides meat, milk and hides but manure and traction as well. In many areas of the tropics, demand for meat and milk products far outstrips supply and the deficit is met by expensive imports paid for with scarce foreign currency. Self-sufficiency in livestock products should be seen as a national goal as well as an important source of farm income. However, as was stressed in the introduction, integration of livestock and trees should not be seen in isolation from the farming system as a whole. Only if the new technologies are carefully tailored to the particular requirements of individual farming communities are they likely to prove acceptable. It is in this respect that agroforestry is likely to provide the major challenge to agricultural scientists and extension workers alike in the 21st century.