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

The reduction in net CO2 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 (N2O) emissions after tillage reversal on long-term NT soils. The objective of this work was to quantify N2O emissions after tillage reversal on two contrasting western Canadian Prairie soils managed under long-term (similar to 30 yr) NT. We measured one growing season (2010) of soil N2O 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 N2O 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 N2O 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 N2O 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.