Fertilizers, agronomy and N2O

N2O is emitted from agricultural soils due to microbial transformation of N from fertilizers, manures and soil N reserves. N2O also derives from N lost from agriculture to other ecosystems: as NH3 or through NO3- leaching. Increased efficiency in crop N uptake and reduction of N losses should in principle diminish the amount of N2O from agricultural sources. Precision in crop nutrient management is developing rapidly and should increase this efficiency. It should be possible to design guidelines on good agricultural practices for low N2O emissions in special situations, e.g. irrigated agriculture, and for special operations, e.g. deep placement of fertilizers and manures. However, current information is insufficient for such guidelines. Slow-release fertilizers and fertilizers with inhibitors of soil enzymatic processes show promise as products which give reduced N2O emissions, but they are expensive and have had little market penetration. Benefits and possible problems with their use needs further clarification.