@ARTICLE {YUSUF:2009c, title = {Effect of crop rotation and nitrogen fertilization on yield and nitrogen efficiency in maize in the northern Guinea savanna of Nigeria}, author = {Yusuf, A. A. and Iwuafor, E. * and Abaidoo, R. and Olufajo, O. * and Sanginga, N. }, journal = {African Journal of Agricultural Research}, year = {2009}, volume = {4}, number = {10}, pages = {913--921}, issn = {1991-637X}, }