Grant: Discovery Grants Program - Individual

Canada is committed to reducing greenhouse gas emissions, nitrous oxide (N2O), from nitrogen (N) fertilizer use by 30% in 2030 from 2020 levels. Our team has shown 4R Nutrient Stewardship, "Right Rate, Source, Placement & Timing" of N fertilizer use to reduce direct soil N2O emissions (emitted by microbes in N fertilizer transformations) by >30%. Canada also aims to net-zero emissions by 2050. For success, other sources of N2O emissions as indirect emissions must be controlled. Hydrolysis of urea fertilizers at soil surfaces results in ammonia (NH3) emissions, a fraction is converted to N2O upon deposition to soil, a major indirect N2O source. Using a qualitative method we found subsurface placement of urea fertilizers to eliminate NH3 losses. However, soil conditions, high moisture and established roots, often prevent subsurface placement resulting in surface addition and NH3 loss. We found some inhibitors of urea hydrolysis to reduce NH3 losses from surface-applied urea. There are many available urease inhibitors, but their effectiveness in reducing NH3 losses and the effect of soil type is unknown. Urease inhibitors are not eligible for government cost-sharing programs for concern reduced NH3 losses result in greater direct N2O emissions, pollution swapping. We've found nitrification inhibitors to reduce direct N2O emissions of N fertilizers by more than 30%. There is also concern of pollution swapping with nitrification inhibitors resulting in NH3 build-up and losses for surface-urea placement. The Prairies are the greatest user of N fertilizer in Canada and concern for pollution swapping constrains adoption of individual use of urease and nitrification inhibitors to reduce N2O and NH3 emissions. Ammonia emission from N fertilizers has not been determined for the Prairies due to methodological limitations. My team will use the TGAS-MAN research site, the world's oldest continuous monitoring of N2O & CO2 fluxes by micrometeorological methods of a cropping system, to include NH3 for whole-field emission estimates of four fields at a time. Recently we've pioneered a relatively cheap quantitative dosimeter method to compare more than four treatments for NH3 emissions. For our team's journey toward net-zero food production, this program addresses a major gap, reducing indirect emissions of N2O from NH3 losses from N fertilizers. The program goals are to discover; a) field emissions of NH3 using micrometeorological methods and benefit of inhibitors to reduce net emissions (N2O, CO2, NH3), b) if NH3 emission estimates are similar for a micrometeorological and a newly developed quantitative dosimeter chamber method, c) the most effective urease inhibitors and what soil types they are effective to reduce NH3 losses, and d) using micrometeorological and chamber-based methods if pollution swapping should prevent eligibility of single inhibitor products in cost-sharing programs. Implications are to position a path to net-zero crop production.