1. Department of Agricultural Economics, Extension, and Rural Development, University of Pretoria, Pretoria, South Africa
2. G-EAU, Univ Montpellier, AgroParisTech, BRGM, CIRAD, INRAE, Institut Agro, IRD, Montpellier, France
3. CIRAD, UMR G-EAU, Hatfield, South Africa