1. Department of Agricultural Extension and Rural DevelopmentFederal University of Agriculture Abeokuta 110124 Nigeria
2. Faculty of Life and Environmental SciencesShimane University Matsue 690‐8504 Japan
3. CSIR–Crop Research InstituteAcademy Post Office Kumasi AE-0680-9724 Ghana
4. Department of Soil ScienceUniversity of Nigeria Nsukka 410001 Nigeria
5. Faculty of AgricultureKinki University Nara 631‐8505 Japan