C. K. Daudu, E. Uyovbisere, E. Iwuafor and O.E. Asiribo
International Journal of Soil Science 1 ( 2 ): 118 - 127 , 2006
C. K. Daudu, E. Uyovbisere, I. Y. Amapu and J. E. Onyibe
Journal of Agronomy 5 ( 2 ): 220 - 227 , 2006