Improved N application methods and N sources for corn in Southwestern Ontario

Corn producers often apply nitrogen (N) fertilizer by either streaming urea-ammonium nitrate (UAN) or broadcasting urea onto the soil. They are considering adding inhibitors to reduce losses of applied N. Compared to other N sources, urea and UAN fertilizers have higher risks of ammonia loss. As with other N sources, denitrification and nitrous oxide (N₂O) losses can also be substantial. The objectives of this project are to measure the impact of these N sources, and their timing and placement, on yields, ammonia loss, and nitrous oxide emissions.

Phase 1 of this study compared treatments applied at sidedress in 2013 and 2014. The inhibitors and the band-injection treatments had large beneficial effects on reducing losses. Compared to broadcast urea, on average over the two years, injection of UAN with urease and nitrification inhibitors increased yields by 19% to 174 bu/A, while reducing loss of ammonia-N by 98% to less than 1 lb/A, and reducing N₂O-N emission during the growing season by 30% to 1.5 lb/A.

Phase 2 of this study started in 2015 and expanded the treatments to include the timing of N fertilizer application. Averaged over the past two years, injecting UAN at sidedress, in comparison to broadcast urea at planting, increased yield by 23% to 203 bu/A, reduced N₂O-N emission during the growing season by 42% to 1.3 lb/A, and reduced ammonia-N emission by 96% to 0.8 lb/A.

This experiment is to be continued in 2017, to account for interactions of the source, timing, and placement factors with weather. The results from this project demonstrate that the implementing the 4Rs (right source, rate, time, and place) for N management can dramatically improve sustainability of corn production in terms of productivity, profitability and environmental impact.