1. Facultad de Agronomía; Instituto de Edafología; Universidad Central de Venezuela; Av. Universidad vía de El Limón; 2101 Maracay Venezuela
2. Department of Soil Management; Faculty of Bioscience Engineering; Ghent University; Coupure Links 653; 9000 Ghent Belgium
3. Aarhus University; Department of Agroecology; Research Centre Foulum; Blichers Allé 20; P.O. Box 50; 8830 Tjele Denmark
4. Department of Geology; Faculty of Sciences; Ghent University; Krijgslaan 281/S8; 9000 Ghent Belgium