Manure Application Methods Do Not Drive N₂O Emissions in a Hayfield

Manure injection is an alternative manure application method that can reduce nitrogen and phosphorus runoff as well as decrease ammonia emissions. However, compared with the more typical practice of spreading manure on the soil surface, manure injection has been shown to increase emissions of nitrous oxide (N₂O), a greenhouse gas with a warming potential 273 times that of carbon dioxide, therefore presenting an environmental trade‐off.

Because many previous studies of greenhouse gas emissions from manure injection were conducted in annual cropping systems, scientists at the University of Vermont examined whether there would still be elevated N₂O fluxes when injecting manure in a perennial hayfield. In a two‐year field trial in Vermont, they found that mean daily N₂O fluxes were comparable in the manure injection and surface manure application treatments. Rather than manure application method, soil moisture was the most important predictor of daily N₂O fluxes, followed by soil inorganic nitrogen and soil temperature. Soil moisture and temperature interacted to produce the largest daily N₂O fluxes when both were relatively high.

These results suggest that injecting manure during dry periods or during wet but cool periods could reduce its climate impacts.