Developing a country specific method for estimating nitrous oxide emissions from agricultural soils in Canada

Accurate estimates of nitrous oxide (N 2 O) emissions from agricultural soils and management factors that influence emissions are necessary to capture the impact of mitigation measures and carry out life cycle analyses aimed at identifying best practices to reduce greenhouse gas emissions. We propose improvements to a country specific method for estimating N 2 O emissions from agricultural soils in Canada based on a compilation of soil N 2 O flux data from recent published literature. We provide a framework for the development of empirical models that could be applied in regions where similar data and information on N 2 O emissions are available. The method considers spatial elements such as soil texture, topography and climate based on a quantitative empirical relationship between synthetic N-induced soil N 2 O emission factor (EF) and growing season precipitation (P) {N 2 OEF = e (0.00558P−7.7) }. Emission factors vary from less than 0.0025 kg N 2 O-N kg N −1 in semi-arid regions of Canada to greater than 0.025 kg N 2 O-N kg N −1 in humid regions. This approach differentiates soil N 2 O EFs based on management factors. Specifically, empirical ratio factors are applied for sources of N of 1.0, 0.84, and 0.28 for synthetic N, animal manure N and crop residue N, respectively. Crop type ratio factors where soil N 2 O EFs from applied manure- and synthetic-N on perennial crops are approximately 19% of those on annual crops. This proposed approach improves the accuracy of the dominant factors that modulate N 2 O emissions from N application to soils.