The DNDC model was used to estimate direct N2O emissions from agricultural soils in Canada from 1970 to 1999. Simulations were carried out for three soil textures in seven soil groups, with two to four crop rotations within each soil group. Over the 30-year period, the average annual N2O emission from agricultural soils in Canada was found to be 39.9 Gg N2O-N, with a range from 20.0 to 77.0 Gg N2O-N, and a general trend towards increasing N2O emissions over time. The larger emissions are attributed to an increase in N-fertilizer application and perhaps to a trend in higher daily minimum temperatures. Annual estimates of N2O emissions were variable, depending on timing of rainfall events and timing and duration of spring thaw events. We estimate, using DNDC, that emissions of N2O in eastern Canada (Atlantic Provinces, Quebec, Ontario) were approximately 36% of the total emissions in Canada, though the area cropped represents 19% of the total. Over the 30-year period, the eastern Gleysolic soils had the largest average annual emissions of 2.47 kg N2O-N ha-1 y-1 and soils of the dryer western Brown Chernozem had the smallest average emission of 0.54 kg N2O-N ha-1 y-1. On average, for the seven soil groups, N2O emissions during spring thaw were approximately 30% of total annual emissions. The average N2O emissions estimates from 1990 to 1999 compared well with estimates for 1996 using the IPCC methodology, but unlike the IPCC methodology our modeling approach provides annual variations in N2O emissions based on climatic differences.
