1. Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK
2. AGRA-Sustainably Growing Africa’s Food Systems, Westends Tower, Nairobi 00100, Kenya
3. Division of Agricultural and Environmental Science, School of Biosciences, Faculty of Science, Sutton Bonington Campus, University of Nottingham, Sutton Bonington, Leicestershire LE12 5RD, UK
4. Inorganic Environmental Geochemistry, Department of Environment Systems Sciences, Swiss Federal Institute of Technology, ETH Zurich, Universitätstrasse 16, 8092 Zurich, Switzerland
5. Department of Water Resources and Drinking Water, Swiss Federal Institute of Aquatic Science and Technology, Eawag, Überlandstrasse 133, 8600 Dübendorf, Switzerland
6. International Maize and Wheat Improvement Centre (CIMMYT), c/o ILRI/CIMMYT, Addis Ababa P.O. Box 5689, Ethiopia
7. Centre for Soil, AgriFood and BioSciences, Cranfield University, Cranfield, Bedfordshire MK43 0AL, UK
8. Adet Agricultural Research Centre, Adet, Bahir Dar P.O. Box 08, Ethiopia