Carbon and nitrogen dynamics in paddy soils from the perspective of iron-reducing nitrogen-fixing bacteria

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K15423
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 38010:Plant nutrition and soil science-related
• Research Institution: The University of Tokyo
• Principal Investigator: Masuda Yoko 東京大学, 大学院農学生命科学研究科(農学部), 助教 (80813237)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 水田土壌 / 鉄還元窒素固定菌 / 稲わら / 安定同位体 / SIP

Outline of Final Research Achievements

Bacteria utilising rice straw-derived carbon were identified by SIP using paddy soil microcosms supplemented with 13C-labelled rice straw. As a result, iron-reducing bacteria incorporated 13C derived from rice straw from the early stages of culture. Rice straw-derived organic acids and sugars were also identified and quantified using GCMS. The results indicated that rice straw-derived carbon compounds were quickly consumed and little remained in the soil.
Paddy soil microcosms containing 15N2 in the gas phase were prepared to verify that the iron-reducing diazotrophs actually fix nitrogen. The amount of nitrogen fixed in the soil was also calculated using IRMS.
This study revealed that iron-reducing diazotrophs utilise rice straw-derived carbon and increase the nitrogen fertility of paddy soils.

Free Research Field

土壌微生物学

Academic Significance and Societal Importance of the Research Achievements

代表者が発見した「鉄還元菌窒素固定」は、窒素固定の従来の常識を覆す新知見であった。本研究は水田土壌の自律的な窒素肥沃度維持の微生物メカニズムとして、稲が鉄還元菌窒素固定を駆動して土壌の窒素肥沃度(地力)を高め、それを利用して稲が生育するとの新概念、「稲が土を肥やし土が稲を育てる」を提唱し検証したものであり、実際に水田土壌で起きている事象の完全解明という学術的な意義だけでなく、将来的に低窒素施肥農業技術を支える基盤となる社会的意義も持つ。