Long-term Effect of Conventional and No-Tillage Production Systems on Nitrous Oxide Fluxes from Corn (Zea mays L.) Field in Southwestern Quebec

Problem statement: There is a growing trend in the adoption of conservation tillage as an alternative to conventional tillage farming system. Implications of this agricultural management shift with respect to nitrous oxide (N₂O) emission, which has been a topic of intense research for the past few decades, is not yet completely understood. Approach: This study was conducted on a 2.4 ha field located at Macdonald research farm of McGill university, Montreal, to investigate the relative impact of long-term Conventional Tillage (CT) and No-Tillage (NT) practices on soil N₂O fluxes (F_N2O) under grain and silage corn (Zea mays L.) during the 2003 and 2004 growing seasons (May-Sept). Nitrous oxide fluxes were measured using static closed chamber by taking gas samples at 0, 10, 20 and 30 min. Results: In both years, the N₂O fluxes were generally similar between the two tillage systems, with the exception of few sampling dates at the beginning of the growing season when N₂O emissions measured under CT were significantly (p≤0.05) greater than NT. Despite our efforts to reduce experimental error by deploying six chambers per treatment plots, spatial and temporal variations were high which might had obscured the treatment differences to be detected. Conclusion: An important implication of present findings was that, contrary to many reports in the literature, the adoption of NT may not add to concerns over global atmospheric N₂O concentrations. This might be due to a greater rate of N₂O reduction to N₂ in soils under NT than CT during diffusion up the soil profile because of the higher moisture content under NT system than CT.