Browsing by Author "Powell, J. M."
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- Alternatives to crop residues for soil amendmentPowell, J. M.; Unger, P. W. (Wallingford, U.K: CABI, 1997)In semiarid agroecosystems, crop residues can provide important benefits of soil and water conservation, nutrient cycling, and improved subsequent crop yields. However, there are frequently multiple competing uses for residues, including animal forage, fuel, and construction material. This chapter discusses the various uses of crop residues and examines alternative soil amendments when crop residues cannot be left on the soil.
- Livestock, nutrient cycling, and sustainable agriculture in the West African SahelPowell, J. M.; Williams, Timothy O. (London, UK: International Institute for Environment and Development (IIED), 1993)This paper addresses the issue of nutrient cycling by livestock in the West African Sahel. Its basic premise is that an efficient cycling of nutrients between soils, crops and livestock is vital to the sustained productivity of farming systems in the Sahel. It reviews traditional linkages between ruminant livestock (cattle, sheep and goats) and soil productivity, and assesses the adequacy of such practices in light of changes taking place in the region. It concludes by suggesting ways in which nutrient cycling could be improved and made part of a broader strategy to enhance sustainable crop-livestock production in the West African Sahel.
- Nutrient cycling on integrated rangeland/cropland systems of the SahelPowell, J. M.; Fernández-Rivera, S.; Hiernaux, P.; Turner, M. D. (1996)In the Sahel of West Africa, the productivities of rangelands, croplands and livestock are inextricably linked. Cattle, sheep and goats graze rangelands and crop residues, and their manure/urine is used to fertilize crops. Rangelands provide important feeds during the manuring period, resulting in a net nutrient transfer from rangelands to croplands. This paper examines the sustainability of nutrient transfers in integrated rangeland/cropland systems of the Sahel by examining the impact of grazing on rangeland vegetation structure and floristic composition, the impact of livestock on nutrient balances of rangelands and croplands, and the role of livestock in offsetting nutrient deficits through manuring. Rangeland nutrient balances are in equilibrium (inputs = offtakes) whereas croplands lack the internal capacity to replenish nutrient offtakes in grain (as food) and crop residues (as feed). Although soil nutrient mining is of general concern for the Sahel, local management practices of some farmers (e.g. corralling animals overnight on fields between cropping seasons, use of fertilizers) offset cropland nutrient deficits. The number of additional livestock, and their feed requirements needed to supply sufficient manure to offset cropland nutrient deficits, depend on rangeland and cropland productivity, livestock production goals, and management strategies of farmers. Livestock must be managed so they do not deplete the nutrient supply of rangelands in order to increase the manure supply for improving cropland productivity. Sustained rangeland productivity in the Sahel will depend largely on producing alternative feeds derived mostly from croplands. Land use and tenure policies that inhibit livestock mobility and, therefore, farmers' access to the manure of pastoralists herds, will greatly undermine the resilience of Sahelian rangelands, and increase the need for other external nutrient inputs such as fertilizers to prevent declines in soil fertility and crop yields. (CAB Abstract)