Assessing Agronomic Nitrogen Management to Mitigate Environmental and Economic Losses in Western Canadian Prairies.

Agronomic nitrogen management is critical for sustainable crop production. Nitrogen use efficiency in Western Canadian prairies ranges from 30-50% depending upon crops, soils and weather conditions. Remaining nitrogen can be prone to losses to air (emissions of N₂O, NH₃ and inert N₂ gases) and to water (nitrate leaching) resulting in substantial environmental and financial losses. The 4R (Right source at the Right place, Right time and Right rate) nutrient stewardship has potentials for minimizing these losses. However, quantifiable estimates of potential environmental and economic savings from 4R nutrient stewardship in Western Canada are still scarce. This project is a proof of concept that aimed to evaluate a process-based ecosystem model "ecosys" to derive numerical estimates of nitrogen losses from alternative N-fertilizer management scenarios differing in their sources, timings, placements and rates across different soils in the Western Canadian province of Alberta under varying weather conditions, and agronomic management. Preliminary site-level model validation showed initial promises of this approach. Modeled outputs of grain carbon and nitrogen uptakes and soil N₂O emissions corroborated reasonably well against field measurements over 4 site years (2008-2011) for two sources (Urea and ESN), two timing (fall and spring), one placement (banding), and three rates (0, 60, and 120 kg N ha^-1 yr^-1) across black, brown, and gray soil zones of Alberta under barley cultivation. After site-level validation, the modeling protocol was scaled up to derive township level (~10 km × 10 km) provincial estimates of agronomic nitrogen losses in Alberta. An economic analysis will follow to help producers identify how much financial savings/gains can be made by adopting beneficial 4R nutrient management practices. Hence, this project will provide the basis for Western Canadian producers with alternative options to identify beneficial nutrient management practices for environmentally sustainable and economically viable crop production.