1. Department of Agricultural Engineering, School of Engineering Sciences, University of Ghana, Accra P.O. Box LG 77, Ghana
2. FSNet-Africa, University of Pretoria, Hatfield 0028, South Africa
3. School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
4. Centre for Agricultural Research and Development, Lilongwe University of Agriculture and Natural Resources, Lilongwe P.O. Box 219, Malawi