CIESIN Thematic Guides

Reducing Nitrous Oxide Emissions from Nitrogenous Fertilizer

Nitrogenous fertilizers play an important role in increasing crop yields, but also release nitrous oxide (N2O) to the atmosphere as a result of microbial action in the soil. Although several options exist for increasing fertilizer efficiency or reducing fertilizer requirements, the U.S. Office of Technology Assessment (1992) states that the extent to which emissions can be reduced is not yet known in Changing by Degrees. Technical practices that can be employed to reduce N2O emissions include more efficient fertilizer application; use of low N2O-emitting fertilizer; use of slow-release fertilizers and nitrification inhibitors; and reduction of leguminous sources of nitrogen. Because of the importance of legumes to food security, however, this last option is probably not feasible.

Preparing U.S. Agriculture for Global Climate Change surveys strategies for decreasing agricultural N2O emissions in the section Nitrous Oxide (Emitting Less) (Council for Agricultural Science and Technology 1992). Fertilizer management through nitrogen-management practices is essential: optimizing the crop's natural ability to compete with processes that result in loss of plant available nitrogen from the soil-plant system (denitrification and leaching); and decreasing the rate and duration of these loss processes. Irrigation water management helps move soluble nitrogen deeper into the soil profile where supplies of oxygen are more limited, and therefore there is increased opportunity to reduce nitrous oxide that may form nitrogen. Figure 5.4.3 shows cumulative nitrous oxide and nitrogen flux at the soil surface for two months as a function of irrigation frequency.

Chapter 7 of the U.S. Environmental Protection Agency report Policy Options for Stabilizing Global Climate discusses a broad range of existing and emerging technologies to reduce nitrous oxide from nitrogenous fertilizers (Lashof and Tirpak 1990).