Tillage effects on N₂O emission from soils under corn and soybeans in Eastern Canada

Abstract

The ways in which agricultural soils are managed influence the production and emission of nitrous oxide (N 2 O). A field study was undertaken in 2003, 2004, and 2005 to quantify and evaluate N 2 O emission from tilled and no-till soils under corn (Zea maysL.) and soybeans (Glycine max L. Merr) in Ontario. Overall, N 2 O emission was lowest in 2003, the driest and coolest of the 3 yr. In 2004, the significantly larger annual N 2 O emission from no-till soils and soils under corn was attributed to an episode of very high N 2 O emission following the application of fertilizer during a period of wet weather. That the N loss by N 2 O emission occurred only in no-till soils and was large and long-lasting (~4 wk) confirms the strong effect that management has in reducing fertilizer N losses. In 2005, tilled soils had significantly larger N 2 O emission than no-till soils, most of which was emitted before the end of June. Because the tilled soils were better aerated , nitrification was likely the primary process contributing to the larger emission. Relatively low N 2 O emission from soybeans suggests biological N fixation does not appear to contribute substantially to the annual N 2 O emission. Further study of methods to reduce N 2 O emission in agricultural systems should focus on improving N use efficiency within a particular tillage system rather than looking to differences between tillage systems. Key words: Tillage, corn, soybeans, nitrogen, nitrous oxide, biogenic gas emission, nitrification, denitrification, fertilization