Partitioning Nitrification Derived N2O Emission from Ammonia Oxidizing Bacteria (AOB) and Ammonia Oxidizing Archaea (AOA)

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N₂O is a potent greenhouse gas and its global warming potential is 298 times higher than carbon dioxide (CO₂). In 2013, 74% of the total N₂O emission in the U.S. was due to agricultural soil management. Therefore, understanding the sources of N₂O emission is critical for developing future mitigation practices and achieving a more sustainable agriculture. Nitrification, a process that oxidizes ammonia into nitrite, is considered as one of the major sources of N₂O emitted from soil. Previous studies showed that both soil AOB and AOA were able to produce N₂O via nitrification but their relative contributions are still poorly understood. We used acetylene (C₂H₂), an inhibitor that inactivates AOA and AOB ammonia monooxygenase (AMO), and Octyne, an inhibitor that specifically inhibits AOB AMO, to investigate how AOA vs. AOB contribute to N₂O emissions in an agricultural soil. In short-term laboratory incubations of freshly collected soils, we found that AOA contributed 33% of total nitrification (NO₂^- + NO₃^-) over 12 hours in aerobic soil slurries and 30% of accumulated N₂O.