Nitrogen Use Efficiency – State of the Art

Authors

Achim R. Dobermann, University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

6-2005

Comments

Paper presented at the IFA International Workshop on Enhanced-Efficiency Fertilizers, Frankfurt, Germany, 28-30 June, 2005.

Abstract

Nitrogenous fertilizers have contributed much to the remarkable increase in food production that has occurred during the past 50 years (Smil, 2001). Globally, however, N fertilizers also account for 33% of the total annual creation of Nr or 63% of all anthropogenic sources of reactive nitrogen (Nr) (Table 1). Reactive nitrogen is defined as all biologically, photochemically, and/or radiatively active forms of N -- a diverse pool of nitrogenous compounds that includes organic compounds (e.g. urea, amines, proteins, amides), mineral N forms, such as NO₃^- and NH₄⁺ as well as gases that are chemically active in the troposphere (NOx, NH₃, N₂O) and contribute to air pollution and the greenhouse effect (Galloway et al., 1995). Asia alone accounts for more than 50% of the global N fertilizer consumption as well as 37% for the global Nr creation. Smil (1999) estimated that only about half of all anthropogenic N inputs to cropland are taken up by harvested crops and their residues, with the remainder contributing significantly to Nr enrichment of the atmosphere, ground and surface waters.