Reduce Nitrous Oxide Emissions
Nitrous oxide (N2O) is a greenhouse gas hundreds of times more powerful than carbon dioxide. Agricultural operations account for 60% of N2O emissions in California. For more in-depth coverage about N2O emissions, check out our N2O emissions focus topic page.
Large bursts of N2O result when soil N levels are elevated and soils are relatively wet. Avoiding excess soil nitrate, particularly when soils are wet, can help minimize N2O emissions from agriculturally managed soils.
While some N2O emissions are unavoidable, emissions can be minimized by taking the steps outlined on this page. In general, practices that reduce N2O emissions also increase fertilizer efficiency.
Minimize Excess Soil Nitrogen
Nitrogen that remains in the soil after crop uptake can be utilized by microbes that produce N2O. Applying the proper amount of nitrogen fertilizer can therefore help limit the production of this greenhouse gas.
Construct a Nutrient Management Plan
Considering all these potential N sources when determining N application rates reduces N2O emissions by limiting the amount of N available to microbes that produce N2O.
For more information about nutrient budgeting, take a look at our nitrogen management and budgeting page.
Adjust Fertilization Rates Mid-season
Changes in temperature and precipitation can alter how N behaves in the soil, so pre-season N management plans should be adjusted based on in-season N levels. An easy, on-farm 'quick test' for soil nitrate allows for the adjustment of N application rates on the fly.
Comparing results of the ‘quick test’ to established threshold values can tell you whether crops will show yield responses with additional fertilization. Threshold values have been identified for a variety of California crops.
For each crop, three threshold values are supplied. The early season level refers to pre-plant soil nitrate tests, whereas the mid-season and late-season refer to those two points in the plant growth cycle. The exact time point considered "mid-season" or "late-season" varies depending on the crop. The values found under "mid-season" and "late-season" refer to the amount of time into the crop growth cycle that the supplied values are relevant. For a summer lettuce crop with an expected 70 day growth period, the mid-season threshold level would be relevant at 14 days (0.2 x 70 = 14) and the late-season value at about 52-53 days (0.75 x 70 = 52.5).
Time Fertilizer Applications to Peak Crop Demands
Crops N requirements change over the course of the season. Timing N applications to periods of maximum N demand can limit excess soil N and suppress N2O emissions.
For example, a fall planted barley crop takes up a relatively small amount of N through the winter and N demand peaks at the stem elongation stage. Therefore N applied at tillering, if followed by rain or irrigation, ensures efficient fertilizer uptake while limiting excess soil N and associated N2O emissions. 
Timing of nutrient requirements vary depending on the crop. Visit the CDFA fertilization guidelines for crop specific information.
Minimize Excess Soil Moisture
Targeted irrigation systems allow for the application of smaller amounts of water throughout the season. By minimizing excess soil water, rates of N2O production can be kept in check.
Subsurface drip irrigation has been shown to reliably reduce N2O emissions. In almond orchards, microsprinkler irrigation has been shown to reduce N2O emissions even more than surface drip. 
To learn more about implementing targeted irrigation systems, visit the Irrigation Training and Research Center website.
- Baethgen, W.E., C.B. Christianson, and A.G. Lamothe, Nitrogen fertilizer effects on growth, grain yield, and yield components of malting barley. Field Crops Research, 1995. 43(2): p. 87-99.
- Alsina, M.M., A.C. Fanton-Borges, and D.R. Smart, Spatiotemporal variation of event related N2O and CH4 emissions during fertigation in a California almond orchard. Ecosphere, 2013. 4(1).