NirS-type N2O-producers and nosZ II-type N2O-reducers determine the N2O emission potential in farmland rhizosphere soils
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Denitrification process in agricultural fields is a large source of nitrous oxide (N2O) emitted to the atmosphere. The rhizosphere soils tend to be the hotspots of denitrification in agricultural soils. Recent studies have reported the important role of nosZ II in eliminating N2O. However, little was known about how these more recently discovered N2O-reducing microorganisms together with other N2O-producers affected the N2O emission in agricultural rhizosphere soils.
Materials and methods
Here, we compared the potential N2O production rate, the denitrification end-product ratio, and the denitrifier communities between rhizosphere and non-rhizosphere soils of two types of crops in winter and summer. The potential activities were measured by acetylene inhibition technique. QPCR analysis was used to quantify the functional genes. High-throughput sequencing and clone library were conducted to analyze the community structure of denitrifiers.
Results and discussion
The rhizosphere soils had a higher N2O production potential but lower denitrification end-product ratio (N2O/(N2O+N2)) than the non-rhizosphere soils. The potential N2O production rate was correlated to the nirS-bacteria abundance, especially in terms of the genus Azospirillum. The N2O/(N2O+N2) ratio showed a negative correlation with both the diversity and abundance of the nosZ II-type N2O-reducers.
Altogether, we propose that nirS-type N2O-producers and nosZ II-type N2O-reducers can affect the N2O emission in agricultural rhizosphere soils, and enhancement of diversity and abundance of nosZ II-type N2O-reducers may help with the N2O mitigation from upland crops.
KeywordsFarmland N2O-producers N2O-reducers nosZ II Rhizosphere soils
This research is financially supported by the National Natural Science Foundation of China (Nos. 41671471, 41322012, and 91851204), Strategic Priority Research Program of the Chinese Academy of Sciences (XDB15020303), National Key R&D Program (2016YFA0602303), Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01Z176), special fund from the State Key Joint Laboratory of Environment Simulation and Pollution Control (Research Center for Eco-environmental Sciences, Chinese Academy of Sciences) (18Z02ESPCR), Open Research Fund of Key Laboratory of Drinking Water Science and Technology, Chinese Academy of Sciences (16Z03KLDWST), and Program of the Youth Innovation Promotion Association (CAS).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
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