2023 Fiscal Year Final Research Report

Methane bubble behaviors in soils and predictive models of methane transport in soils

Research Project

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Project/Area Number	19K22921
Research Category	Grant-in-Aid for Challenging Research (Exploratory)
Allocation Type	Multi-year Fund
Review Section	Medium-sized Section 64:Environmental conservation measure and related fields
Research Institution	Hokkaido University (2023) The University of Tokyo (2019-2022)
Principal Investigator	Hamamoto Shoichiro 北海道大学, 農学研究院, 教授 (30581946)
Co-Investigator(Kenkyū-buntansha)	常田岳志国立研究開発法人農業・食品産業技術総合研究機構, 農業環境研究部門, 上級研究員 (20585856) 小島悠揮岐阜大学, 工学部, 准教授 (70767475)
Project Period (FY)	2019-06-28 – 2024-03-31
Keywords	メタン / バブル態メタン / 水田 / 溶存メタン濃度
Outline of Final Research Achievements	The objective of this study was to elucidate the characteristics of methane gas emissions from paddy fields, including bubble-form methane fluxes. Field monitoring conducted in FY2021 and FY2022 showed that bubble-form methane fluxes were higher in the early and late growth stages when the aeration tissue of rice plants was immature or possibly degraded, and that a non-negligible proportion of bubble-form methane against the total methane fluxes The initial application of rice straw was also found to increase the release of bubble-form methane in the early growth stages. Based on the relationship between the amount of bubbles in the soil and the methane fluxes, we proposed a predictive model to estimate the methane flux at different pathways.
Free Research Field	土壌物理学
Academic Significance and Societal Importance of the Research Achievements	本研究成果から、水田からのバブル態メタン放出の季節変動を明らかにした。従来、水田からのメタン放出は水稲経由が主であると考えられており、本研究成果は水田からのメタン放出機構におけるバブル態メタン放出の重要性を示したもので学術的意義は高い。また、土壌内のバブル存在量を関数とする形態別メタンフラックス予測式を提案した。比較的測定が容易な土壌気相率の連続モニタリングデータから水田におけるメタン放出フラックス予測の可能性を示し、温室効果ガス放出源としての水田の正確な評価に繋がる成果が得られた。