Impacts of enhanced efficiency nitrogen fertilizer type and application timing on N2O emission reductions in irrigated wheat fields
Ogilvie, C., E. Daly, R.L. Lemke and R.E. Farrell . 2026.
Abstract
Context: Irrigation increases crop productivity but may also increase emissions of nitrous oxide (N2O), a potent
greenhouse gas and stratospheric ozone-depleting substance, partly due to the higher nitrogen (N) fertilizer
inputs often required. However, there is a paucity of field data from the Canadian Prairies evaluating the
effectiveness of enhanced efficiency nitrogen fertilizers (EENFs) under irrigated conditions, despite the importance of this region to Canadian agriculture. Here we evaluated the efficacy of several EENFs and application
timing (fall vs. spring) for mitigating N2O emissions in a semi-arid irrigated spring wheat cropping system, with
the goal of generating field-based evidence to support mitigation recommendations and to contribute to the
development of regionally relevant EFs.
Methods: The study was conducted over 2.5 years in the Dark Brown Soil Zone of Saskatchewan using a randomized complete block design. Conventional granular urea was compared to a controlled release polymer-
coated urea (PCU), urea with a nitrification inhibitor (NI; nitrapyrin), urea with dual action urease inhibitors
(UI; N-(butyl) thiophosphoric triamide [NBPT] N-(propyl) thiophosphoric triamide [NPPT]), and urea with
both a urease inhibitor (NBPT) and an NI (UNI; dicyandiamide [DCD]). Emissions of N2O were measured using
non-steady state vented chambers and soil N dynamics were monitored using Plant Root Simulator (PRS)®
probes.
Results: PRS® probe measurements of nitrate (NO3-) and ammonium (NH4+) supply rates confirmed the expected effects of EENFs on soil N transformations. The PCU, UNI, and UI modulated NH4 + whereas the EENFs with an NI (NI and UNI) modulated NO3- supply compared to urea,
supply. Both NI-containing EENFs reduced cumulative and fertilizer-induced N2O emissions by 50-80% and 77-83%, respectively, with the greatest reductions occurring when spring-applied. The UI showed inconsistent effects, reducing N
spring-applied. No yield differences were observed among treatments.
Conclusions: Applying a urea-based fertilizer with an NI substantially reduced N2O emissions from a semi-
aridirrigated spring wheat cropping system regardless of application timing, without increases in crop yield.
Thus, mitigating N losses as N2O and modifying soil mineral N dynamics did not translate into greater crop productivity.
Implications: These findings underscore the importance of integrating regionally-tailored fertilizer source and
timing within the 4 R Nutrient Stewardship framework best management practices (BMPs) and demonstrate the
potential of EENFs to mitigate N2O emissions in irrigated cropping systems in semi-arid cereal cropping systems.
Key Words
Enhanced efficiency fertilizer, N2O, 4R Nutrient Stewardship
