Impacts of inhibitor use on nitrous oxide and ammonia emissions, nitrate leaching and resulting crop yields

The demand for food is increasing rapidly as a consequence of global population growth and changes in patterns of food consumption. One of the most important changes in the global agri-food system has been the intensification of production systems and the increase in fertiliser nitrogen (N) use. Improved grasslands are an important part of this intensification process and constitute a significant share of the agricultural area in some temperate countries. It is expected that further intensification will occur to meet the increasing global demand for livestock products, putting pressure on farming that will likely result in increased N use.

N fertiliser use is directly related to productivity, but it also has major environmental effects. In many cases fertiliser rates exceed crop requirements, leading to an N surplus, reduced N use efficiency (NUE) and risking losses to the environment through nitrate leaching and gaseous emissions of nitrous oxide and ammonia. In grazed grasslands, risks of losses are even higher, due to the excreta N deposited during grazing. Improved NUE is needed to reduce the negative effects of an N surplus while preserving productivity and soil fertility.

Nitrification inhibitors (to reduce nitrous oxide emissions) and urease inhibitors (to reduce ammonia emissions) are two commercially available options for reducing losses to the environment and improving NUE. This paper summarises the latest research testing both. It covers factors that control the efficacy of the inhibitors on losses and also pasture yields, including the economic costs and benefits of using inhibitors.