Nitrous oxide emissions with enhanced efficiency and conventional urea fertilizers in winter wheat

Citation

An, H., Owens, J., Beres, B., Li, Y., Hao, X. (2021). Nitrous oxide emissions with enhanced efficiency and conventional urea fertilizers in winter wheat, 119(3), 307-322. http://dx.doi.org/10.1007/s10705-021-10118-9

Plain language summary

Reducing greenhouse gas emissions from agriculture is required to mitigate climate change. One strategy to do this from soils cropped with winter wheat may be modifying fertilizer type or application time. If these strategies better match N crop demand with fertilizer supply, excess soil N may be reduced, which may reduce nitrous oxide (N2O) emissions. Nitrous oxide is a potent greenhouse gas implicated in climate change. A three-year field trial tested whether enhanced efficiency fertilizers, which alter N availability from urea and different application times, influenced N2O emissions. We tested three different enhanced efficiency fertilizers (polymer-coated urea, urea with urease and nitrification inhibitor, and urea with nitrification inhibitor) that were split applied 30% banded at planting and 70% broadcast in late fall, or split applied 30% banded at planting and 70% broadcast at Feekes growth stage 4 (GS4, post-tiller formation, wheat entering the “greening up” phase in the early spring) compared to urea applied 100% at planting. Annual fertilizer rates ranged from 146 to 176 kg N ha-1. Over three years, cumulative N2O emissions ranged from 0.16 to 1.32 kg N ha-1. This was equivalent to between 0.009 and 0.688% of the nitrogen applied as fertilizer lost as N2O. We found that enhanced efficiency fertilizers did not lower N2O emissions, but emissions were lower when fertilizer was split applied at GS4 compared to in late fall. This suggests that rainfed winter wheat crops in Southern Alberta looking to minimize N2O emissions should consider a well-timed split application with a majority of fertilizer applied after winter rather than investing in enhanced efficiency fertilizers.

Abstract

© 2021, Crown.Optimizing nitrogen fertilizer management can reduce nitrous oxide (N2O) emissions. This study tested if split applying enhanced efficiency fertilizers (EEFs) resulted in lower N2O emissions than applying equivalent rates of urea at planting. In semiarid southern Alberta, field trials were conducted during three years (planting to harvest) in rainfed winter wheat crops. Annual fertilizer rates ranged from 146 to 176 kg N ha−1. Fertilizer types were urea, and three EEFs (polymer-coated urea, urea with urease and nitrification inhibitors, and urea with a nitrification inhibitor). Each fertilizer type was applied three ways: 100% banded at planting, split applied 30% banded at planting and 70% broadcast in late fall, and split applied 30% banded at planting and 70% broadcast at Feekes growth stage 4 (GS4, post-tiller formation, wheat entering the greening up phase in the early spring). Nitrous oxide was measured using static chambers between sub-weekly and monthly from planting to harvest. Over three years, cumulative N2O emissions ranged from 0.16 to 1.32 kg N ha−1. This was equivalent to emissions factors between 0.009 and 0.688%. Cumulative N2O emissions and emissions factors did not differ between fertilizer types, but they were lower when fertilizer was split applied at GS4 compared to in late fall (P ≤ 0.10). Our study suggests that EEFs do not reduce N2O emissions from rainfed winter wheat crops, but a well-timed split application with a majority of fertilizer applied after winter can minimize N2O emissions.

Publication date

2021-04-01