OMAFA: Cover crops and nitrous oxide emissions

Aug 28, 2024

Cover crops help build soil carbon, reduce erosion, and can offset crop nitrogen fertilizer requirements. But when it comes to nitrous oxide (N₂O) – a greenhouse gas that contributes about half the total warming effect from agriculture in Canada – there is a question mark surrounding their benefit.

The primary driver of nitrous oxide emissions from agricultural soils is denitrification, which is promoted by wet soils, ample available mineral nitrogen (e.g. nitrate), the presence of carbon sources and freeze-thaw cycles. Cover crops influence each of these conditions. A 2014 meta-analysis found that cover crops decreased N₂O emissions in 40 per cent of studies and increased them in the other 60 per cent.

The following factors determined cover crop effects on emissions:

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Video: Residue Management

Residue Management conservation practice manages the amount, orientation, and distribution of crop and other plant residue on the soil surface year-round while limiting soil-disturbing activities used to grow and harvest crops in systems where the field surface is tilled prior to planting. This video explores how Ryan McKenzie implemented this conservation practice on his farm in Samson, Alabama.

Practice benefits:

• Increases organic matter

• Improves air quality

• Decreases energy costs

• Reduces erosion

• Improves soil health

The Conservation at Work video series was created to increase producer awareness of common conservation practices and was filmed at various locations throughout the country. Because conservation plans are specific to the unique resource needs on each farm and also soil type, weather conditions, etc., these videos were designed to serve as a general guide to the benefits of soil and water conservation and landowners should contact their local USDA office for individual consultation.