Nitrification inhibitors in agriculture

Nitrification inhibitors can retard or prevent the conversion of ammonium‐nitrogen to nitrate‐nitrogen by nitrifying bacteria in soil. Application of an inhibitor with ammonium or ammonium‐forming fertilizers will limit the formation of nitrate which, unlike ammonium, is susceptible to loss from soil by leaching and denitrification. Many diverse compounds will inhibit nitrification although for agricultural use some are more feasible than others. Results from numerous field experiments covering a range of crops, soil types and cultivation practices indicate where inhibitor use may be beneficial or detrimental, in terms of increased yield and recovery of fertilizer nitrogen by a crop. Commercial use of inhibitors will probably increase, due to increased fertilizer costs, legislation to limit nitrate inputs to groundwaters and nitrate concentrations in crops, and the increased use of fertilizers such as urea which are suitable for application with an inhibitor.