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Abstract

No-till farming in wheat is being practiced in the rice–wheat system of the Indo-Gangetic plains of south Asia for resource conservation. No-tillage leads to mitigation of carbon dioxide emission, but may emit more nitrous oxide (N 2 O) as compared to conventional tillage reducing mitigation benefit. The aim of this study was assessment of N 2 O emission in wheat grown under conventional and no-tillage and its mitigation using two new nitrification inhibitors, viz. S-benzylisothiouronium butanoate (SBT- butanoate) and S-benzylisothiouronium furoate (SBT-furoate). Cumulative emission of N 2 O-N was higher under no-tillage by 12.2% with urea fertilization and from 4.1 to 4.8% for the inhibitor treatments as compared to the conventional tillage. In no-tillage total emission of N 2 O-N reduced from 0.43% of applied N with urea to 0.29% of applied N with SBT-furoate treatment. The N 2 O-N emissions in SBT- butanoate treatment were at par with the standard dicyandiamide (DCD) inhibitor treatment. Water- filled pore space (WFPS) was higher on most days under no-tillage, with the largest emissions (>1000 mg N 2 O-N m 2 day 1 ) coming with nitrification of ammonium-N present in soil below 60% WFPS. Carbon efficiency ratio was highest (48.1) from SBT-furoate treatment under conventional tillage. The nitrification inhibitors used in the study increased yield of wheat, reduced global warming potential by 8.9–19.5% over urea treatment and may be used to mitigate N 2 O emission. A. a, *, S. a , N. a , H. a , R. b , A.