@INBOOK {COUPER:1980, title = {Mechanical no-till maize production in an alfisol in tropical Africa}, author = {Couper, D. C. and Lal, R. and Claassen, S. L. }, year = {1980}, type = {IITA publication edited by R. Lal - Crop Production and Soil Tillage}, publisher = {International Institute of Tropical Agriculture (IITA)}, address = {Ibadan, Nigeria}, }