@INBOOK {IKEORGU:1989b, title = {Effect of fertilizer and time of introduction of cassava or maize on productivity of yam and cassava-based intercrops in a humid ultisol}, author = {Ikeorgu, J. * and Unamma, R. P. A. and Ezumah, H. C. }, year = {1989}, type = {Cassava-based cropping systems research II}, pages = {36--41}, publisher = {International Institute of Tropical Agriculture (IITA)}, address = {Ibadan, Nigeria}, note = {RTB; Root and Tuber; Cassava}, }