Biochar amendment mitigated N2O emissions from paddy field during the wheat growing season

Qianqian Zhang; Zhen Wu; Xi Zhang; Pengpeng Duan; Haojie Shen; Anna Gunina; Xiaoyuan Yan; Zhengqin Xiong

doi:10.1016/j.envpol.2021.117026

Biochar amendment mitigated N₂O emissions from paddy field during the wheat growing season

Environ Pollut. 2021 Jul 15:281:117026. doi: 10.1016/j.envpol.2021.117026. Epub 2021 Mar 27.

Authors

Qianqian Zhang¹, Zhen Wu², Xi Zhang², Pengpeng Duan³, Haojie Shen², Anna Gunina⁴, Xiaoyuan Yan⁵, Zhengqin Xiong⁶

Affiliations

¹ Jiangsu Key Laboratory of Low Carbon Agriculture and GHGs Mitigation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China; Georg-August University of Göttingen, Department of Soil Science of Temperate Ecosystems, Department of Agricultural Soil Science, Büsgenweg 2, 37077, Göttingen, Germany.
² Jiangsu Key Laboratory of Low Carbon Agriculture and GHGs Mitigation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
³ Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, Hunan, China.
⁴ Department of Environmental Chemistry, University of Kassel, Nordbahnhof Strasse 1a, 37213, Witzenhausen, Germany.
⁵ State Key Lab of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China.
⁶ Jiangsu Key Laboratory of Low Carbon Agriculture and GHGs Mitigation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China. Electronic address: zqxiong@njau.edu.cn.

PMID: 33813196
DOI: 10.1016/j.envpol.2021.117026

Abstract

Biochar may variably impact nitrogen (N) transformation and N-cycle-related microbial activities. Yet the mechanism of biochar amendment on nitrous oxide (N₂O) emissions from agricultural ecosystems remains unclear. Based on a 6-year long-term biochar amendment experiment, we applied a dual isotope (¹⁵N-¹⁸O) labeling technique with tracing transcriptional genes to differentiate the contribution of nitrifier nitrification (NN), nitrifier denitrification (ND), nitrification-coupled denitrification (NCD) and heterotrophic denitrification (HD) pathway to N₂O production. Then the field experiment provided quantitative data on dynamic N₂O emissions, soil mineral N and key functional marker gene abundances during the wheat growing season. By using ¹⁵N-¹⁸O isotope, biochar decreased N₂O emission derived from ND (by 45-94%), HD (by 35-46%) and NCD (by 30-64%) compared to the values under N application. Biochar increased the relative contribution of NN to total N₂O production as evidenced by the increase in ammonia-oxidizing bacteria, but did not influence the cumulative NN-derived N₂O. The field experiment found that the majority of the N₂O emissions peaked following fertilization, in parallel with soil NH₄⁺ and nitrite dynamics. Soil N₂O emissions during the wheat growing stage were effectively decreased (by 38-48%) by biochar amendment. Based on the correlation analyses and random forest analysis in both microcosm and field experiments, the decrease in nitrite concentration (by 62-65%) and increase in N₂O consumption were mainly responsible for net N₂O mitigation, as evidenced by the decrease in the ratios of nitrite reductase genes/transcripts (nirS, nirK and fungal nirK) and N₂O reductase gene/transcripts (nosZI and nosZII). Based on the extrapolation from microcosm to field, biochar significantly mitigated N₂O emissions by weakening the ND processes, since NCD and HD contributed little during the N₂O emission "peaks" following urea fertilization. Therefore, emphasis should be put on the ND process and nitrite accumulation during N₂O emission peaks and extrapolated to all agroecosystems.

Keywords: Biochar; Gene/transcripts abundance; Nitrifier denitrification; Nitrite accumulation; Nitrous oxide.

MeSH terms

Charcoal
Denitrification
Ecosystem
Nitrous Oxide / analysis
Seasons
Soil
Soil Microbiology*
Triticum*

Substances

Soil
biochar
Charcoal
Nitrous Oxide