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The effects of split application of enhanced efficiency fertilizers on non-winter nitrous oxide emissions from winter wheat.

Owens, J., H. An, B. Beres, R. Mohr and X. Hao. 2019. NRC Research Press

Abstract

This study tested if non-winter cumulative nitrous oxide (N2O) emissions, emission factors, and yield-scaled N2O emissions were affected by split application of enhanced efficiency nitrogen fertilizers in a rain-fed winter wheat crop. Based on initial soil tests, fertilizers were applied at 84 kg N ha-1 in year 1 and 72 kg N ha-1 in year 2. Two trials were completed each year. Trial 1 applied (1) urea, (2) urea with nitrification inhibitor, (3) nitrification and urease inhibitors, and (4) polymer-coated urea as (1) 100% side-banded at planting, 30% side-banded at planting and (2) 70% surface-applied in late fall, or (3) 70% surface-applied in spring at Feekes growth stage 4 (GS4). Trial 2 applied (1) urea- ammonium nitrate (UAN), (2) UAN treated with nitrification inhibitor, (3) urease inhibitor, (4) a combination of both, (5) granular urea, and (6) polymer-coated urea, all applied 50% side-banded at planting and 50% surface-applied at GS4. Cumulative N2O emissions from fertilized soils ranged from 0.101 to 0.433 kg N ha-1. The emission factors for trial 1 were greater in year 1 than year 2 (P≤0.05). There were no treatment differences in cumulative N2O emissions in trial 2. However, cumulative N2O emissions, emission factors, and yield-scaled N2O emissions from trial 1 were higher when fertilizer was split-applied in late fall compared with at GS4 (all P≤0.05). This study demonstrates that under best management practices, it is better to apply the required rate in the form of conventional fertilizer at planting rather than split application.

Key Words

nitrification inhibitors, urease inhibitors, polymer-coated urea, urea