Can Organic Crop Production be a Potential N2O Mitigation Strategy?.

Can organic crop production be a N₂O mitigation strategy?

Megan Westphal^1*, Mario Tenuta¹, Martin Entz^2
1 Department of Soil Science, University of Manitoba, Winnipeg R3T 2N2
² Department of Plant Science, University of Manitoba, Winnipeg R3T 2N2
^* Contact: westphme@cc.umanitoba.ca

N₂O is one of the greenhouse gases that is suggested to emit less in organic agriculture systems, however studies have found emissions can be both lower or greater than conventional cropping systems. Few studies have compared greenhouse gas emissions between conventional and organic cropping systems with particular attention to the contribution of soil N₂O the fall plow down of alfalfa in Canada and not well understood. In the current study, the Glenlea Long-Term Organic Crop Rotation Study near Winnipeg was used to monitor N₂O emissions. In 2014 and 2015, organic perennial alfalfa, organic spring wheat which follows the plow down of alfalfa, and conventional wheat, and conventional soybean were monitored using the vented static chamber method. Soil conditions and agronomic measures were also determined. Both organic spring wheat and organic alfalfa had lower cumulative N₂O emissions; 144 and 100 g N₂O-N/ha respectively, compared to the conventional wheat and conventional soybean 622 and 243 g N₂O-N/ha respectively. The 2014 fall plow down of alfalfa showed a minimal N₂O episode both after plow down (0.52g N₂O-N/ha/day) and during spring thaw (1.8 g N₂O-N/ha/day). However lower yields in the organic spring wheat may offset the environmental benefits of lower N₂O emissions. Full crop year daily flux, cumulative emissions will be presented relative to yield, and grain protein.