Keywords: nitrification, denitrification, nitrous oxide, nitric oxide, N simulation models, chemodenitrification, nitrite.

One consequence of the intensification of fertilised agriculture in the 20th century has been enhanced emissions of nitric oxide (NO) and nitrous oxide (N₂O) from soils to the atmosphere. These trace gases are critical in regulating important processes including global warming, tropospheric and stratospheric ozone chemistry, and N deposition to downwind ecosystems. Understanding the mechanisms responsible for NO and N₂O production and transformation in soil are important in order to better assess present sources, predict future trends, and develop mitigation strategies. We review the mechanisms responsible for NO and N₂O production in soil and discuss the soil and environmental factors affecting these processes. Field techniques for measuring emissions of NO and N₂O from soil to the atmosphere are described. Existing empirical, deterministic and stochastic emission models are discussed, and important research needs are proposed.

Dennis E. Rolston, Land, Air and Water Resources, University of California, Davis, CA, USA
Rodney T. Venterea, Institute of Ecosystem Studies, Millbrook, NY, USA

36 pages, 6 figures, 200 refs.