Nitrogen fertilizers release greenhouse gases (GHG) both in their production and application. In their production, synthetic fertilizers are produced from natural gas, a non-renewable fossil fuel that contributes to climate change. In their use, atmospheric nitrogen (N2) is converted into forms that crops need to grow, such as nitrates (NO3-), in a process known as fixation. Nitrous oxide (N20), a GHG product of the nitrogen fertilizer life cycle, has a global warming potential that is 298 times more potent than CO2. By emitting this strong greenhouse gas, humans increase warming in the atmosphere and consequently overall climate change.
Therefore, it is important to effectively manage nitrogen fertilizer to use only what the crops need, and to reduce losses due to emissions or runoff. Nitrogen fertilizer is also a costly input, so optimizing its use can save farmers money. Conditions to look out for that can lead to high nitrous oxide emissions include saturated soils, high soil temperatures, and high pH soils. Organic fertilizers (such as manure, compost or tilled-in cover crops) can be an alternative to synthetic nitrogen fertilizer. In addition to reducing nitrous oxide emissions, organic fertilizers improve soil health, as well as water and nutrient retention.
For more information on the nitrogen fertilizers and GHG emissions, feel free to refer to the following fact sheets and tools from Cornell, Cornell Cooperative Extension, and the USDA: CCE Nitrogen Fact sheet: http://nmsp.cals.cornell.edu/publications/factsheets/factsheet2.pdf;
N2O Emissions Fact Sheet: http://nmsp.cals.cornell.edu/publications/factsheets/factsheet90.pdf