| Project/Area Number |
09660257
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Irrigation, drainage and rural engineering/Rural planning
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| Research Institution | Gifu University |
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Principal Investigator |
MATSUMOTO Yasuo Gifu University, Faculty of Agriculture, Professor, 農学部, 教授 (30021728)
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| Co-Investigator(Kenkyū-buntansha) |
MIYAKE Yasunari Gifu University, Faculty of Agriculture, Assistant Professor, 農学部, 講師 (60262755)
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| Project Period (FY) |
1997 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 1998: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1997: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Keywords | Reclaimed Farmlamd / Slope Farming / Drainage Ditch / Soil Erosion / Diluvial Ash Soil / Sedimentation Tank / Stream Polution |
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| Research Abstract |
In Japanese sloping farmlands, stream muddy pollution has been caused by soil erosion at heavy storms. This study was concerned to make the actual relations between slope farming and stream pollution clear and to propose the conservation practices from the viewpoint of sustainable agriculture. The results obtained were as follows.
[Characteristics of stream pollution] Installing a self-recording turbidity-meter at just the front of sedimentation reservoir and in it, we observed turbididy fluctuations. Measurements showed that turbidities of inflow water were sensitive to short rainfall distributions and rised steeply up to 1,000 mg/l and recover to the original clear conditions after rainfall for a short time. On the other hand, turbidities in the reservoir were over 1,000 mg/l after only heavy storms of 10 mm/10min. Sedimentation reservoirs were considered to be restricted to control the stream muddy pollution.
[Sediment source and factors affecting soil loss] we analysed soil erosion f
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actors affected by the field conditions (size and slope), furrowing practices, waterway ditch setups and raddish growing stages by the multiple regression method. The volume of soil loss was traced in 24 selected test fields installed a sedimentation tank. Soil loss was violent after heavy storms of over 10 mm/10min and varied. Multiple regression analysis showed clearly that soil loss was mainly caused by ditch setups along the end of furrows.
[Waterway ditch profiles] In severe soil loss fields, the longitudinal profiles of ditches had gentle gradient at the lower parts without native grass and steep one at the upper parts. On the other hand, mild soil loss fields had relatively steep ditches at the lower parts with native grass growing and more gentle one at the upper parts by sedimentation. Renewal of the ditches removing grass caused severe erosion losses.
[Conservation farming] Soil erosion was controlled by the ditches protection of sand bags setup conducting sedimentation at intervals with native grass growing up after the renewal. Attention should be paid at the lower parts stagnation of runoff at heavy storms which caused serious soil erosion by the upstream ridge break down. Less
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