1. Boue‐Sols 28, rue du Général Frère Vandoeuvre‐lès‐Nancy 54500 France
2. IRD, UMR IEES‐Paris Sorbonne Université/IRD/CNRS/INRAe/UPEC/Université de Paris Centre IRD de France Nord, 32, Av. H. Varagnat, 93143 Bondy Cedex France
3. Mangosuthu Univ. of Technology Community Extension Jacobs 4031 South Africa
4. South African Sugar Association Experiment Station Private Bag X02 Mount Edgecombe 4300 South Africa
5. Dep. of Soil, Crops and Climate Sciences Univ. of the Free State PO Box 339 Bloemfontein 9300 South Africa