Managing Nitrogen Inputs to Reduce Nitrous Oxide Emissions

What is nitrous oxide?

Nitrous oxide is a greenhouse gas. When compared to carbon dioxide, nitrous oxide is often described as a “more potent” greenhouse gas – this is because nitrous oxide is 300 times stronger than carbon dioxide in its ability to heat the atmosphere and can remain there for over 100 years. Nitrous oxide emissions have risen globally by 30% over the past 40 years and there is evidence that agricultural soils can be a major contributor to these emissions¹.

How is nitrous oxide produced in agricultural soils?

Nitrous oxide is produced through a process called denitrification.
Denitrification occurs when microorganisms transform nitrogen in the soil (nitrate and nitrite) into gas form (nitrous oxide and nitrogen gas).
Denitrification is one of the key forms of nitrogen loss from soils, alongside leaching, volatilization, and runoff.

What conditions lead to an increase in denitrification?

High soil moisture (a.k.a. anaerobic conditions).
Warm soil temperatures.
Inefficient use of nitrogen inputs.

For Consideration:

Which of these components are you most able to influence?

What can we do to reduce denitrification and nitrous oxide emissions in agricultural soils?

Although research into the specifics of how we can mitigate the risk of nitrous oxide emissions in Canadian cropping systems is ongoing, there is good evidence that using nitrogen inputs efficiently is an opportunity to lower agricultural nitrous oxide emissions.² We have learned through previous posts that the 4 R’s of Nitrogen Management can be used to guide nitrogen management decisions.

How can we apply the 4 Rs of Nitrogen Management to nitrous oxide management?

Right Source

Use enhanced efficiency fertilizers (e.g. nitrification inhibitors and urease inhibitors).
Consider inputs that release nitrogen more slowly (e.g. compost, manure, and digestates).

Right Rate

Choose nitrogen application rates that do not exceed the needs of the crop being grown.
Take annual soil samples to determine the contributions of nitrogen that may be pre-existing in the soil.
Take measures to account for potential carry-over of nitrogen from previous years of compost/manure applications or nitrogen-fixing cover crops (if applicable).

Right Placement

Apply fertilizers close to roots to improve uptake of nitrogen (e.g. include more targeted application techniques and reduce broadcast applications where possible).

Right Timing

Avoid applying nitrogen when soils are expected to remain wet for a long period of time, such as around a long stretch of wet weather.
Apply smaller amounts of fertilizer multiple times a year (e.g. use split-applications), instead of only one large application, to avoid excess amounts of nitrogen existing in the soil for longer than necessary.

Other Methods to Consider

Implement drainage improvements in poorly-drained fields.
Use cover crops to take up excess nitrogen, especially during wet months.
Implement no-till or low-tillage practices, where possible.

Learn more about agricultural nitrous oxide emissions:

¹Tian, H. et al. (2020). A comprehensive quantification of global nitrous oxide sources and sinks. Nature. 586(7828): 248–256. https://doi.org/10.1038/s41586-020-2780-0

²Chahal, I. et al. (2021). Opportunities to reduce nitrous oxide emissions from horticultural production systems in Canada. Canadian Journal of Plant Science. 101(6): 999-1013. https://doi.org/10.1139/cjps-2021-0107