Effects of phosphorus fertilizer sources on cowpea and subsequent cereal crop productivity in semi-arid West Africa

abonos fosfatados application rates cultivars dose d'application efectos residuales fosfato mineral mais maize phosphate fertilizers phosphate naturel residual effects rock phosphate rotation culturale rotational cropping sorghum bicolor superfosfato superphosphate variedades varieties vigna unguiculata zea mays