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SOIL BIOLOGY & BIOCHEMISTRY

Carbon Dioxide and Nitrous Oxide Fluxes in Corn Grown under Two Tillage Systems in Southwestern Quebec

^a Programa de Edafologia, Colegio de Postgraduados, Montecillo, Estado de Mexico, Mexico 56230
^b Dep. of Plant Science, Macdonald Campus, McGill Univ., 21111 Lakeshore Rd., Ste. Anne de Bellevue, QC, Canada H9X 3V9
^c Brace Center for Water Resources Management, Macdonald Campus, McGill Univ., 21111 Lakeshore Rd., Ste. Anne de Bellevue, QC, Canada H9X 3V9
^d Agriculture and Agri-Food Canada, 2560 Hochelaga Blvd., Sainte-Foy, QC, Canada G1V 2J3
^e Eastern Cereal and Oilseed Research Centre (ECORC), Agriculture and Agri-Food Canada, 960 Carling Ave., Ottawa, ON, Canada K1A 0C6

^* Corresponding Author (donald.smith{at}mcgill.ca).

Agriculture has an important potential role in mitigating greenhouse gas emissions (GHG). However, practices that reduce CO₂ emissions from soils and increase the soil organic C level may stimulate N₂O emissions. This is particularly critical in Quebec where heavy soils and a humid climate may limit the adoption of agricultural practices designed to mitigate GHG. The objective of this work was to study the effects of two tillage and N fertilization regimes on CO₂ and N₂O fluxes and the seasonal variability in emissions of these gases, associated with corn (Zea mays L.) grown in southwestern Quebec. Different seasonal emission patterns of CO₂ and N₂O were observed. Higher N₂O fluxes occurred during the spring and were associated with precipitation events, while higher CO₂ fluxes occurred in mid-season and were related to temperature. Conventional tillage (CT) had greater peaks of CO₂ emissions than no-till (NT) only after disking in the spring. Once corn was established, differences between tillage systems were small. Peaks of N₂O emission occurred in both systems (NT and CT) following N application. Plots receiving 180 kg N ha^–1 in both tillage systems had large peak of N₂O emission rates during the wettest parts of the season. The CT and NT systems generally had similar cumulative CO₂ emissions but NT had higher cumulative N₂O emissions than CT. Our findings suggests that changing from CT to NT under the heavy soil conditions of Quebec may increase GHG, mainly as result of the increase in N₂O emission. This negative effect of NT could be reduced by avoiding fertilizing when precipitation is more intense.

Abbreviations: CT, conventional tillage • GHG, greenhouse gas emissions • NT, no-till • WFPS, water-filled pore space