This report, jointly commissioned by the International Fertilizer Association (IFA) and the Food and Agriculture Organization of the United Nations (FAO), is based on the work of A. Bouwman and L.J.M. Boumans (both from the National Institute Public Health and the Environment, Bilthoven, the Netherlands) and N.H. Batjes (International Soil Reference and Information Centre, Wageningen, the Netherlands). The report benefited from contributions from P. Botschek (European Fertilizer Manufacturers Association, Brussels, Belgium), W. Bussink (NMI Research Station for Cattle, Sheep and Horse Husbandry PR, Lelystad, the Netherlands), S.K. de Datta (College of Agriculture & Life Sciences, Virginia Tech, Blacksburg, Virginia, USA), T. Denmead (CSIRO, Canberra, Australia), K. Isherwood (IFA, Paris, France), E. Kreileman (National Institute of Public Health and the Environment) J. Küsters and M. Laegreid (both from Hydro Agri, Dülmen, Germany), H.-J. Michel and H. Wozniak (both from SKW Stickstoffwerke Piesteritz GmbH, Cunnersdorf, Germany), A.R. Mosier (USDA-Agricultural Research Station, Fort Collins, Colorado, USA), J. Plummer, J. Poulisse (FAO), M. Prud'homme (IFA) and T. van den Bergen (FAO).