[1] Wageningen Univ, Plant Prod Syst, POB 430, Wageningen, Netherlands
[2] World Wildlife Fund, POB 7, Zeist, Netherlands
[3] Wageningen Univ, Human Nutr & Hlth, POB 17, Wageningen, Netherlands
[4] Hawassa Univ, Coll Agr, Hawassa, Ethiopia
[5] Int Inst Trop Agr IITA, POB 10, Arusha, Tanzania