Short-term effects of tillage of long-term no-till on nitrous oxide emissions from two contrasting Canadian prairie soils

The reduction in net CO 2 emissions from increased carbon sequestration in soil and slower decomposition of soil organic matter under most long-term no-till (NT) situations can potentially be offset by a concomitant increase in nitrous oxide (N 2 O) emissions after tillage reversal on long-term NT soils. The objective of this work was to quantify N 2 O emissions after tillage reversal on two contrasting western Canadian Prairie soils managed under long-term (∼30 yr) NT. We measured one growing season (2010) of soil N 2 O emissions on a Black Chernozem and Gray Luvisol at Ellerslie and Breton, AB, respectively, following 30 yr of NT and N fertilizer application at two rates (0 and 100 kg N ha −1 ) subjected to tillage reversal and no disturbance (i.e., continuing NT). Tillage reversal after long-term NT was associated with higher N 2 O emissions in both soils but was significant only in the Gray Luvisol with 0 kg N ha −1 . Long-term N fertilizer applications of 100 kg N ha −1 were associated with higher growing season soil N 2 O emissions and higher levels of soil N (i.e., a positive, long-term soil N balance) at both sites. Regardless of tillage, the difference in growing season nitrous oxide emissions from the 0 and 100 kg N ha −1 plots on the Gray Luvisol were much greater than the Black Chernozem. A modest increase in N 2 O emissions upon tillage reversal on a long-term NT soils could translate to a significant increase to agricultural greenhouse gas inventories in the event of large-scale tillage reversal on agricultural land in western Canada.