Rotational effects of cowpea genotypes and P fertilization on the yield of sorghum on P-deficient soils of Sudan and Sahel savannas of west Africa - Saidou, A.K.; Abaidoo, Robert C.; Iwuafor, E.N.O.; Sanginga, Nteranya; Singh, B.B.; Kolawole, G.O. (International Center for Tropical Agriculture, 2007)