1. Dep. of Soil Science and Land Management; College of Plant Science and Crop Production, Univ. of Agriculture, Abeokuta; P.M.B. 2240 Abeokuta Ogun State Nigeria
2. Dep. of Soil Science; School of Human and Environ. Science, Univ. of Reading; Whiteknights Campus, PO Box 233 Reading RG6 6DW UK