1. Dep. of Soil Management; Ghent Univ.; Coupure Links 653 B-9000 Ghent Belgium
2. Research Unit on Environment and Conservation of Natural Resources; National Institute of Agricultural Research; BP 415, Avenue de la Victoire 10000 Rabat Morocco
3. Dep. of Soil Sciences and Land Reclamation, Faculty of Agriculture; Aleppo Univ.; Aleppo Syria
4. Dep. of Soil Sciences and Land Reclamation, Faculty of Agriculture; Damascus Univ.; Damascus Syria