1. Dep. of Soil Management, Soil Physics Unit; Ghent Univ.; Coupure Links 653 (B) Ghent 9000 Belgium
2. Dep. of Geology and Soil Science, Lab. of Soil Science; Ghent Univ.; Krijgslaan 281 (S8) Ghent 9000 Belgium
3. Norwegian Institute for Agricultural and Environmental Research- BIOFORSK; Frederik A. Dahls vei 20 Aas 1432 Norway
4. Dep. of Natural Resources Management; Univ. of Kinshasa; Campus Kinshasa Kinshasa Democratic Republic of Congo