The Century model was used to estimate the influence of changing agricultural practices on C levels in seven major soil groups in Canada for the years from 2000 to 2010. Conversion of arable land to permanent cover, and inclusion of forages in crop rotations would result in the greatest sequestration of C, averaging 0.62 and 0.44 Mg C ha-1 yr-1, respectively. The increase in soil C when conventional-tillage is converted to no-tillage management was estimated to average about 0.13 Mg C ha-1 yr-1. Reduction of summerfallow (wheat-fallow to wheat-wheat-fallow) in the arid and semi-arid chernozems of Western Canada would reduce C losses by about 0.03 Mg C ha-1 yr-1. If fertilizer use efficiency was increased by 50%, 0.04 Mg C ha-1 yr-1 would be sequestered, whereas a decrease of 50% in fertilizer use efficiency would result in a loss of 0.05 Mg C ha-1 yr-1. Timing of N application (fall vs. spring) had little effect on C change. This study indicates that there are several feasible techniques that could be adopted by agricultural producers in Canada that would significantly increase CO2 uptake from the atmosphere. Although our estimates are based on changes in individual management options, we recognize that producers are likely to adopt several options at the same time. Any interactions resulting from such a move have not been assessed in this analysis, in particular the impact on N2O emissions. Key words: Soil carbon, CO2, C sequestration, Century model, soil, tillage, agricultural practices, nitrous oxide emissions, crop rotations
