| Project/Area Number |
16KT0151
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 特設分野 |
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| Research Field |
Food Cycle Research
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| Research Institution | Kumamoto University |
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Principal Investigator |
Ichiyanagi Kimpei 熊本大学, 大学院先端科学研究部(理), 准教授 (50371737)
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| Research Collaborator |
Hososo Takahiro
Suzuki Yaeko
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| Project Period (FY) |
2016-07-19 – 2019-03-31
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| Project Status |
Completed (Fiscal Year 2018)
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| Budget Amount *help |
¥4,680,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥1,080,000)
Fiscal Year 2018: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2017: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2016: ¥2,860,000 (Direct Cost: ¥2,200,000、Indirect Cost: ¥660,000)
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| Keywords | 地下水 / 窒素汚染 / 自然栽培水田 / 自然農法 / 水田 / 窒素収支 / 自然農法水田 / 硝酸性窒素 / 水質汚濁・土壌汚染防止・浄化 / 環境調和型農林水産 |
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| Outline of Final Research Achievements |
In this study, the nitrogen and water budgets were investigated in a naturally-farmed paddy field covered an area of about 1,000 m2 that was not treated with pesticides, or chemical and organic fertilizers. The nitrate ion concentrations in soil water at a depth of 60 cm were very low, so the nitrate load to groundwater was considered very low. Cause nitrogen isotope compositions in soil organic matter and rice paddy were both about +10‰, it was estimated that soil organic matter was the nitrogen source of rice paddy in this field.
As a result of the groundwater model simulation in case that all paddy fields are changed to the naturally-farmed paddy, nitrate ion concentration of groundwater drops within several years around the paddy fields and within 20 years in the downstreams.
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| Academic Significance and Societal Importance of the Research Achievements |
自然栽培水田は栽培が難しく，実際の水田で窒素収支を観測した研究はほとんど無い．また，水田土壌と生育したイネの窒素安定同位体比はどちらも+10‰であり，土壌の有機物起源であると推定できた．これらの成果は，日本初の貴重なデータである．
さらに，熊本地域の水田をすべて自然栽培にする仮定で地下水シミュレーションを行った結果，地下水の硝酸性窒素濃度が下がるのは数年から20年程度という具体的な年数が明らかになった．また，モデルを検証するために収集した河川データより，江津湖の湧水量の再評価や熊本地震の影響を明らかにした．これらの成果は地下水汚染対策に有用であり，社会的な意義が大きいと言える．
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