ABSTRACT
Nitrogen (N) is the mineral nutrient that is most limiting for crop production around the world and is often applied as a fertilizer to maintain adequate soil levels for crop production. Geisseler et al. (2012) reported that adequate N supply is crucial to obtaining high yields in intensive crop production. While insufcient N application can have serious economic consequences for the farmer, excessive fertilization increases the risk of environmental pollution, especially groundwater pollution with NO3
−, NH3 volatilization, and emissions of N2O. Even in a well-managed cereal production system, a substantial fraction (typically 40-60%) of N fertilizer inputs can be lost (Galloway et al., 2002). Dinnes et al. (2002) reported that N is essential for the growth and reproduction of all lifeforms, and except for legume crops and virgin soils with relatively high soil organic matter, soil N must usually be supplemented to sustain food and ber production.
