Nitrous oxide emissions from urea fertiliser and effluent with and without inhibitors applied to pasture

Abstract

© 2015 Elsevier B.V.There is currently a limited number of New Zealand studies quantifying nitrous oxide (N₂O) emission factors (EF₁, N₂O emissions as a percentage of N applied) for farm dairy effluent (FDE) and urea fertiliser. Therefore, two experiments were conducted in four regions of New Zealand to determine EF₁ for FDE and urea fertiliser applied to pastures with contrasting soils and climatic conditions. Experiment 1 included urease and nitrification inhibitors to determine their effect on EF₁. Urea treatments included (i) standard urea; (ii) urea amended with the nitrification inhibitor dicyandiamide (DCD) at 0.02 kg DCD kg⁻¹ nitrogen (N) and (iii) urea amended with the urease inhibitor N-(n-butyl) thiophosphoric triamide (nBTPT) at 250mgnBTPTkg⁻¹urea, while FDE was applied with or without DCD, at 10 kg DCD ha⁻¹. Experiment 2 focused solely on FDE, which was applied to pastures that had either never received FDE or had a history of repeated application of FDE over several years. Urea fertiliser produced a large variation in EF₁ values, ranging from 0.03% to 1.52%. Application of FDE resulted in EF₁ ranging from 0.06% to 0.94% across both experiments. The urease and nitrification inhibitors had little or no effect on reducing EF₁ from urea fertiliser and FDE application. The history of repeated applications of FDE to pasture also had no effect on EF₁.