The fundamental processes that influence nitrate leaching are similar in all farming systems and research into the processes operating in conventional agriculture also contributes to an understanding of N cycles in organic farming. Many of the strategies that have been proposed for reducing N leaching in conventional agriculture are also applicable to organic farming. The relevance of much research to organic agriculture is limited by differences in the organic matter content and biological activity of organically and conventionally managed soils with the result that quantitative information about organic systems cannot always be derived from conventional agriculture. There is a particular need for information about N fluxes in whole-farm systems, particularly those involving grass/arable rotations.