This study is based on the work of Dr Nisar Ahmad, Director of the National Fertilizer Development Centre (NFDC), Pakistan.
The study benefited from the contributions of K. Isherwood, J. Poulisse and T. van den Bergen (FAO).
The photographs are from the FAO Mediabase: background (FAO/23395/A. Mihich), vegetables (FAO/23009/K. Iversen), cotton (FAO/17720/A. Contí) and wheat from Ecocrop/A.J.D. Barket.