Nitrification inhibitors selectively inhibit microbial enzymes responsible for the conversion of NH4+ to NO3-. Arresting nitrification could be a key strategy to improve nitrogen (N) recovery and agronomic N use efficiency in situations where the loss of N is significant. Although chemicals known to inhibit nitrifiers have been tested, many of these are still at the experimental level; high cost, limited availability, adverse influence on beneficial soil microorganisms, and above all, poor extension and promotional activities are major constraints in this respect. It is therefore necessary to develop plant-based nitrification inhibitors (natural nitrification inhibitors, NNI) for augmenting nitrogen use efficiency, crop productivity, and for safeguarding the environment. The advantages of NNI are that they are easily available, cheap, and eco-friendly. This paper briefly reviews the different aspects of plant-based nitrification retarder
