Nitrogen stabilizers to enhance nitrogen use efficiency and reduce greenhouse gas emissions

The main objective of this project is to assess the effect of various commercially available forms of stabilized nitrogen (N) on nitrous oxide (N₂O) emissions, nitrate leaching, nutrient use efficiency (NUE), and crop yield response in cereal and oilseed crops. The experiment used a factorial set of 4R-based treatments involving the form, rate, timing, and placement of N fertilizers. Nitrogen forms included untreated urea, urea treated with both a nitrification and urease inhibitor (Super U®), urea treated with a nitrification inhibitor only (eNtrench®), and a polymer-coated controlled-release urea (ESN®). Nitrogen application rates included 0, 50, 100, and 150% of the local recommended fertilization rates for wheat, specifically 0, 40, 80, and 120 kg N/ha. Timing of N application included fall banded, and pre-plant spring banded. Identical experiments were conducted at two sites, differing in geography and climate (Ellerslie research farm near Edmonton, Alberta on a Black soil; and the Lethbridge Research Station, near Lethbridge, Alberta, on a Dark Brown soil).

There was a significant effect of year and crop on N₂O emissions, and spring fluxes dominated total growing season N₂O emissions. The Lethbridge site also included split application treatments of N fertilizer for both canola and wheat. The rates of total N applied were 0, 30, 60, 90, and 120 kg N/ha. The in-season fertigation applied 30 kg N/ha using urea ammonium nitrate (UAN), and this was part of the total N applied. For example, the 60 kg N/ha rate had 30 kg N/ha applied as urea in a pre-plant operation, and the remaining 30 kg N/ha applied using fertigation-applied UAN. The results analyzed from the 2015 and 2016 years indicate that the split fertigation treatments have lower cumulative N₂O emissions compared to all N fertilizer being applied before planting. The 2017 samples taken for N₂O emissions have all been measured and the data is being analyzed to compare the various experimental treatments. A final report will be completed in 2018.