Nitrogen fertiliser-induced changes in NO emissions are attributed more to ammonia-oxidising bacteria rather than archaea as revealed using 1-octyne and acetylene inhibitors in two arable soils.

Nitrification is believed to be one of the major sources of NO production emitted from soil. Previous studies showed that both ammonia-oxidising bacteria (AOB) and archaea (AOA) can produce NO via nitrification but their relative contributions are still poorly defined. Here, we used acetylene, an inhibitor of AOB and AOA ammonia monooxygenase (AMO), and 1-octyne, a selective inhibitor that specifically inhibits AOB AMO, to investigate how AOB versus AOA contribute to NO emissions in two distinct arable soils. Soil amended with ammonium (NH ) increased NO emissions to a greater extent than nitrate (NO ), and acetylene had a greater impact on NO emissions in NH -treated soils than that in NO -amended soils, which indicated that nitrification was the dominant NO emitting process in these two arable soils. In the alluvial and red soil, the percentage of evolved NO after application of NH by AOB were 70.5 ~ 78.1 % and 18.7 ~ 19.7 % by AOA, respectively. Quantitative PCR revealed that NH addition stimulated AOB growth, and the growth could be significantly inhibited by acetylene or 1-octyne in the two soils. The stimulation of NO emissions by NH and the relative suppression by inhibitors paralleled fluctuations in the AOB growth. In addition, cumulative NO emissions were not correlated with AOA abundance in the two soils. Our results revealed that AOB could contribute more to soil NO production than AOA in the NH -amended arable soils. [ABSTRACT FROM AUTHOR]