[1] Univ Ghent, Dept Geol & Soil Sci WE13, Lab Soil Sci, Krijgslaan 281-S8, B-9000 Ghent, Belgium
[2] Univ Nairobi, Dept Land Resources Management & Agr Technol, POB 29053, Nairobi 00625, Kenya
[3] Univ Ghent, Dept Soil Management BW12, Res Unit Soil Degradat & Conservat, Coupure Links 653, B-9000 Ghent, Belgium