The use of no-till (NT) and improved fertilizer management are proposed ways to sequester atmospheric CO2 in agricultural soils. Previous studies have shown that the potential to sequester C in soils of eastern Canada under NT can be limited. Soil C content was measured in a 13-year old research site comparing the effects of NT, and rates of N (0, 80, 160 kg N ha-1) and P (0, 17.5, 35 kg P ha-1) fertilizers in a corn/soybean system on a clay loam at L'Acadie, Québec. Soil samples were taken in 72 plots at 7 depth increments down to 60 cm during 3 consecutive cropping seasons. The effects of N and P fertilizer rates on soil C content were not significant at any soil depth despite significant effects of N fertilizer on corn yields and consequently on C inputs. In the 0-5 cm soil layer only, C content was significantly greater in the NT than in the mouldboard plow (MP) treatment. Conversely, in the 20-30 cm layer, C content was significantly greater in the MP than in the NT soil. Overall, when assessed for the whole soil profile, there were no significant effect of tillage on soil C storage; the greater C content in the top soil under NT was off-set by greater C content at depth under MP. Analysis of crop yields for the 13 cropping seasons indicated that C inputs were not different between tillage systems. These results confirm the limited impact of tillage practices on C storage in soils of eastern Canada and emphasize the importance of taking the whole soil profile into account when analyzing soil C storage in cropping systems involving mouldboard plowing. Despite significant effects on corn yields, increasing N rates did not result in measurable impact on soil C in this corn/soybean system.