改良山成畑における耕地組織と砂防(生産環境学科)
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概要
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造成農地からの赤土流出の要因は種々ある。本研究は造成完了後の畑地の土砂流亡, 圃場面侵食, 土砂流出の要因解析, 砂防施設の機能等耕地組織と防災施設のあり方を検討したもので, その概要はつぎのとおりである。1.土砂流亡調査において, 濁度は植生圃場やマルチング圃場は無視できる程少ないが, 裸地圃場からの流出は大型沈砂池を通過した流出水でも濁度は高く観測された。2.圃場面侵食調査においては侵食を生ずる圃場面傾斜角度と斜面長の関係はつぎの一次式で表わされる。U=14.69-0.612θここにU : 限界斜面長(m)θ : 傾斜角(度)Uとθの相関関係は0.57で余り高くない。畑面の起状の状態や表土層の物理性が大きく与かっているからである3.パインアップルは植付後約1年間, サトウキビは半年間受食性作物の形態をとるがその後は植生被覆や根による土壌保定効果が現われ, 耐食性の形態をとる。4.大規模な農地造成の際の土砂流出抑止対策としては流出水の一時貯留を図り, 浮遊土砂の河川への直接流出をさけるようにする。5.砂防施設の堆砂機能に関してはTable.3の示すとおりであり流量の如何に関わらず, 水路型の方が高い。There are various factors involved in red soil loss from reclaimed farmland. This is a study which examines farm systems and soil loss control facilities by investigating soil loss from reclaimed farmland, rill erosion, factors contributing to soil loss, and functions of soil erosion control facilities. A gist of the study is as follows : 1. In soil loss surveys, soil loss from vegetated farmland and mulching farmland was negligible, whereas soil loss from bared farmland was high, with a high degree of muddiness even in water from large-scale sedimentation ponds. 2. In rill erosion surveys, the relation between the angle of inclination of the slope being eroded and the length of the slope can be shown in the following linear equation : U=14.69-0.612θ Where U=critical slope length (m) and θ=degree of slope. The relationship of the coefficient of U and θ is 0.58 and not too high, because the conditions of the microtopograhy of the soil surface and the physical characteristics of the surface layer are contributing factors. 3. Pineapples, for about one year after planting, and sugarcane, for about half a year after planting, are both erodible crops, but later become non-erodible crops as they grow to form cover and their roots develops soil catch. 4. In case of a large-sclae farmland reclamation, such soil loss control measures should be taken as building temporary catchments for runoff water and prevention of direct flow into rivers of fluided particles. 5. As to soil precipitating functions of soil erosion control facilities, as shown in Table 3,soil precipitation function is high in channel type Fig. 17 (c), regardless of the rate of discharge.
- 琉球大学農学部の論文
- 1994-12-01
琉球大学農学部 | 論文
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