Greenhouse gas fluxes associated with soybean production under two tillage systems in southwestern Quebec

Agricultural soils are an important contributor to greenhouse gas emissions and the size of this contribution can be influenced by tillage practice and crop. The objective of this work was to study greenhouse gas (carbon dioxide-CO2 and nitrous oxide-N2O) emissions associated with N-2 fixing soybean (Glycine max) grown under two tillage systems (conventional-CT and no-till-NT). The experiment was organized following a randomized complete block design with four blocks. The CO2 and N2O fluxes were evaluated throughout the growing seasons of 2002 and 2003. The seasonal emission patterns were different for CO2 and N2O. Soil CO2 emissions during the season were associated with soil temperature while the N2O fluxes were mainly associated with precipitation. The CT system generally had greater CO2 fluxes than the NT system, particularly in 2002. In that year the maximum peak, which occurred in the summer, was about 160 g m(-2) d(-1) under CT and 68 g m(-2) d(-1) under NT. N2O emissions were low in the first year but high in the second, and were greater for CT than NT with a maximum peak about 18.1 mg m(-2) d(-1) under CT and 7.4 mg m(-2) d(-1) under NT. Our findings suggests that use of NT in the production of N-2 fixing soybean may reduce both CO2 and N2O emissions, in comparison to CT. Soybean residue incorporation increased N2O emissions, leading to greater emissions from the CT production system. (C) 2009 Elsevier B.V. All rights reserved.