Direct emission of nitrous oxide from agricultural soils

This analysis is based on published measurements of nitrous oxide (N2O) emission from fertilized and unfertilized fields. Data was selected in order to evaluate the importance of factors that regulate N2O production, including soil conditions, type of crop, nitrogen (N) fertilizer type and soil and crop management. Reported N2O losses from anhydrous ammonia and organic N fertilizers or combinations of organic and synthetic N fertilizers are higher than those for other types of N fertilizer. However, the range of management and environmental conditions represented by the data set is inadequate for use in estimating emission factors for each fertilizer type. The data are appropriate for estimating the order of magnitude of emissions. The longer the period over which measurements are made, the higher the fertilizer-induced emission. Therefore, a simple equation to relate the total annual direct N2O-N emission (E) from fertilized fields to the N fertilizer applied (F), was based on the measurements covering periods of one year: E = 1 + 1.25 x F, with E and F in kg N ha(-1) yr(-1). This relationship is independent of the type of fertilizer. Although the above regression equation includes considerable uncertainty, it may be appropriate for global estimates.