1. Department of Soil, Crop and Climate Sciences, Faculty of Natural and Agricultural Sciences, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa
2. Agricultural Research Council—Natural Resources and Engineering, Private Bag X79, Pretoria 0001, South Africa
3. Risk and Vulnerability Assessment Centre, University of Limpopo, Private Bag X1106, Sovenga 0727, South Africa
4. Agricultural Research Council—Grain Crops, Private Bag X1251, Potchefstroom 2520, South Africa