Clifford S. Snyder1
Fertilizer nitrogen (N) has been, and will continue to be, essential in nourishing, clothing, and providing bioenergy for the human family. Yet, emissions of ammonia (NH3) and nitrous oxide (N2O), and losses of nitrate-N (NO3-N) to surface and groundwater resources are risks associated with fertilizer N use that must be better managed to help meet expanding societal expectations. Nitrogen fertilizers with polymer coatings, or with addition of urease and/or nitrification inhibitors, or possessing other characteristics that afford them either improved agronomic response and/or lessened loss of N to the environment - compared to a reference water soluble fertilizer - may be considered enhanced efficiency N fertilizers (EEFs). Agronomic and horticultural research with these technologies has been carried out for many decades, but it has been primarily in the last decade that research has increasingly also measured their efficacy in reducing N losses via volatilization, leaching, drainage, runoff, and denitrification. Expanded use of EEFs, within the concept of 4R N management (right source, right rate, right time, right place) may help increase crop yields while minimizing environmental N losses. Coupling these 4R N management tools with precision technologies, information systems, and crop growth and N utilization and transformation models –especially with weather models, may improve opportunities for refined N management in the future.