Nitrous oxide emissions following split fertilizer application on winter wheat grown on Mollisols of Southern Alberta, Canada

Synthetic fertilizer-induced nitrous oxide (N2O) emissions contribute to climate change. Enhanced efficiency fertilizers (EEFs) may reduce soil N2O emissions compared to conventional fertilizers like urea-ammonium-nitrate (“UAN”) and urea by better matching fertilizer N supply with plant N demand. This study tested whether three liquid EEFs (a nitrification inhibitor, “NI”, a urease inhibitor, “UI”, and a urease and nitrification inhibitor, “UI + NI”) and polymer-coated urea (Environmentally Smart Nitrogen, “PCU”) reduced N2O emissions compared to liquid UAN and solid urea from a rain-fed soil located in a cool, semiarid climate. Fertilizer was split applied (between 73 and 88 kg N ha−1 side-banded at planting and broadcast in the spring at Feekes growth stage 4) to winter wheat (Triticum aestivum L.) over three years in Lethbridge, Alberta, Canada. Nitrous oxide fluxes and soil ammonium (NH4+, mg N kg−1) and nitrate (NO3−, mg N kg−1) were measured from planting to harvest. While there were yearly differences detected for cumulative N2O emissions (kg N ha−1, P < .001) and yield-scaled N2O emissions (mg N2O-N kg−1 yield, P < .001), there were no significant differences in cumulative N2O emissions, N2O lost as a percentage of N added as fertilizer (emissions factors), or yield-scaled N2O emissions between fertilizer types. The results of this study show that EEFs applied to semiarid winter wheat crops do not alter N2O emissions or emissions factors compared to conventional fertilizers over the winter wheat life cycle suggesting they have limited benefits for mitigating climate change in the Canadian Prairies.