A critical review of crop-residue use as soil amendment in the West African semi-arid tropics.
1995
Bationo A. | Buerkert A. | Sedogo M.P. | Christianson B.C. | Mokwunye A.U.
Poor soil fertility and low use of organic and inorganic fertilisers are the greatest constraints to increasing agricultural productivity of farming systems in the West African semi-arid tropics (WASAT). Results from long-term field experiments showed that the use of mineral fertilisers alone in the long-run leads to decreasing base saturation, decreasing pH and increasing aluminium (Al) toxicity in soils which might be limiting crop yields. The soil fertility in intensified farming in the WASAT can only be maintained through efficient recycling of organic material such as millet crop residues (CR) or manure in combination with mineral fertilisers and using rotations with legumes such as groundnut and cowpea or Stylosanthes. The mechanisms responsible for the positive effects of CR on crop yields are multiple. They include local conditions such as rainfall, wind speed, soil type, and temperature regime. Thus, at some sites an increase in available phosphorus (P) or potassium (K) may be the most important mechanism while at other sites, the protection against sand coverage and water erosion, a loosening of the upper soil layers, soil microbiological effects or a decrease of soil surface temperature and soil resistance may be dominant. In mixed crop-livestock systems, the issue of competing uses for CR needs to be addressed to understand the current mechanisms of resource allocation by farmers and to design economically and ecologically sound alternatives which ensure the sustainability of current farming systems at a higher output level. The complementary effects between livestock and crop production in the Sahel also suggests that research efforts should not only take into account ways to increase crop biomass at the farm level, but also how to increase the quantity and quality of fodder.
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