ABSTRACT
Nitrate is a naturally occurring form of nitrogen in soil. Despite the soil nitrate concentration being low compared to organic soil nitrogen, it plays a central role in nitrogen cycling in ecosystems. Nitrate is the main source of nitrogen needed for optimal plant production, but at the same time, nitrate is the main N compound linked to water and air pollution, and N2O emission, a greenhouse gas with the potential for ozone layer destruction. The processes which produce and consume nitrate in the soil are complex and include biological processes such as N mineralization coupled with nitrification, assimilatory and dissimilatory nitrate reduction, and physical-chemical processes such as leaching and ammonium volatilization. On the basis of examples, literature reviews, and current knowledge, this chapter provides an overview of the processes relating to nitrate production, consumption, and turnover.
