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The ability to fix N is not the only key to delivery of the benefits of BNF to farmers: experience of IITA in the savannas of Africa
Abstract/Description
The IITA in its research for sustainable soil fertility management has passed through several stages during which legume-based systems were always at the forefront. Alley cropping has N yields of more than 200 kg ha-1 with 50% N2 fixation. In the case of Mucuna cover cropping, the ecological benefit was unequivocal, with more than 100 kg ha' of N2 fixed and consistently positive effects on crop yields. But adoption by farmers has been too low to bring the benefit of BNF to farm households. Based on these experiences, we have proposed increased emphasis on systems based on cowpea and soybean rotation because of their high adoptability although the benefits to the soil are small compared with Mucuna fallows and alley farming. Besides high protein grain production, cowpea and soybean rotation reduced densities of Striga hermonthica by 50% in farmer-managed trials and increased net benefits to farmers. Cover cropping and agroforestry systems can also be used for soil fertility management, but only if their adoptability increases by providing products needed by farmers.