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 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®), a 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. The Lethbridge site also included split applications of N fertilizer, where part of the urea was applied as a pre-plant application, and part as an in-crop fertigation application of urea ammonium nitrate (UAN). At the fertigation site, wheat was grown in 2015 and canola in 2016. In the 2016 fertigation experiment there was an interaction between timing and split of applications and rate of total N. The lowest N₂O emissions were observed in split applications at 90 kg N/ha, but it was observed that N₂O emissions increased when the N rate was increased to 120 kg N/ha.

It would seem that the 120 kg N/ha rate exceeded the need of N by the crop and resulted in excess N available for denitrification losses. All field work has been completed and the experimental results are being analyzed. The final reports will be completed in the Spring of 2017.