Pathways and controls of N2O production in greenhouse vegetable production soils
Here, the combined approaches of a 15N tracing technique, DNA and mRNA analyses, and modeling were used to investigate the mechanisms underlying rapid nitrate (NO3−) accumulation and identify the relative contributions of autotrophic nitrification, heterotrophic nitrification, codenitrification, and denitrification to nitrous oxide (N2O) production in six vegetable soils. The soil pH had a positive effect on the NO3− retention capacity (p < 0.01) and a negative effect on the net NO3− production rate (p < 0.05), resulting in higher NO3− accumulation in acidic soils. Meanwhile, autotrophic nitrification accounted for 39–86% of N2O production in alkaline soils, whereas denitrification was responsible for 85% of N2O production in acidic soils. The results of structural equation modeling indicated that autotrophic nitrification-derived N2O production was influenced by soil C/N ratio, the gross NO3− production rate, and the ammonia-oxidizing archaea (AOA) amoA/ammonia-oxidizing bacteria (AOB) amoA mRNA ratio, while denitrification-derived N2O production was influenced by pH, the gross NO3− consumption rate, and the abundance of nirS mRNA, all of which were influenced directly and indirectly by in situ climate parameters of mean annual precipitation and mean annual temperature. Furthermore, regression analyses revealed that the soil total N content affected heterotrophic nitrification- and the pH affected codenitrification-derived N2O production, which contributed 9–76% and 0–7%, respectively, to the total N2O production in vegetable soils. The current findings improve our understanding of the mechanisms of NO3− buildup and N2O stimulation in intensively managed agricultural ecosystems.
KeywordsIntensive vegetable soil Gross N transformation mRNA NO3− accumulation N2O production pathways
We thank Professor Paolo Nannipieri and two anonymous reviewers for their valuable comments and critical evaluation on this manuscript. We also would like to thank Professor Christoph Müller and Professor Jinbo Zhang for N transformation rates assistance. We also thank Dr. Xianwang Kong and Dr. Bo Li for their many constructive comments.
This work was jointly supported by the National Natural Science Foundation of China (41471192), the Special Fund for Agro-Scientific Research in the Public Interest (201503106), and the Postgraduate Research & Practice Innovation Program of Jiangsu Province, China (KYCX18_0678).
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