Biological nitrification inhibition for sustainable crop production

Abstract The oxidation of ammonium to nitrate by biological process is known as nitrification. This process of nitrification is accomplished by Nitrosomonas spp. and Nitrobacter spp. Current intensive agricultural systems, characterized by heavy-nitrification systems, are prone to greater losses of nitrogen through nitrate leaching and emissions of greenhouse gases (GHGs) such as nitrous oxide, contributing to the increment of global temperature and ozone layer depletion. Furthermore, nitrate, under anoxic or partially anoxic conditions, escapes into the atmosphere as gaseous forms of nitrogen (N2 and N2O) through denitrification. Synthetic nitrification inhibitors (NIs) are used to regulate nitrification process in soil. The NIs are compounds that regulate this process by inhibiting ammonia monooxygenase (AMO) enzymes. Ability of certain plant species to exudate certain organic compounds from roots that have regulatory effect on performance of nitrifying bacteria has been known as biological nitrification inhibition (BNI). It inhibits both AMO and HAO (hydroxylamine oxidoreductase) enzymatic pathway in that process. The compounds are also stable in soil and production of BNI compounds are localized mainly to the rhizosphere and therefore, their modes of action may be more efficient. Brachiaria humidicola, a tropical pasture grass capable of growing in acidic soils and humid environments, is a well-known BNI-capable species that produces biochemical compound known as brachialactone. Cropping system adoption with current move toward ecologically intensified cropping with high nutrient-use efficiency is found to be novel strategy for controlling nitrification process.