Studies on the Reclamation Method for Preventing the Field from the Soil Erosion.

试验田为普通田和草地各5公顷。分别在青森县NANGO村的改良斜坡上进行填海。本项目对该试验场及其水土流失防治机构进行了复垦规划设计。这些围填海规划和设计的效果进行了研究如下：1。一般农田（1）农田地形与土壤侵蚀的相关性明显。具有凸起表面的土地形式分散了雨水，减少了土壤侵蚀。另一方面，凹地形态使径流集中在底部，加剧了底部的土壤侵蚀。因此，田间建设设计应在凸形地形上进行. (2)拦河坝、淤地坝、浅V型断面的草道等田间设施对防止表层土壤侵蚀是有效的。它们有很大的一部分用于径流，可以吸走大量的淤泥，而不会埋在里面。此外，这些都是用成本较低的方法规划和建造的。(3)降雨在农田中的滞留量随开垦年限的增加而增加。这种增加是由于农田土壤层入渗量的增加，而且这种入渗量随着作物根孔的形成和土壤干燥后产生的裂缝而增加。此外，覆土还有助于增加降雨滞留量.玻璃地（1）分级后的土地形态和制度与普通农田相似，取得了较好的效果。复垦过程中未发现塌陷、侵蚀和水体污染。(2)表层土壤的修整和耕作被简化为苗床，种子被推土机而不是拖拉机压下。但通过改良土壤、施肥等措施，可以获得较好的产量和质量。(3)根据草地试验区的真实的状况，对表层土壤硬度进行了调查。

The experimental ordinary field and grassland having 5 ha. respectively are reclamed at improved slope in the NANGO village, AOMORI Prefecture. The reclamation planning and design of this experimental site and its institutions for preventing soil erosion are carried out in this project. The effects of these reclamation planning and design are investigated as follows:1. Ordinary field(1) It is obvious that the field topography correlate to soil erosion. Land form having a convex surfce disperse the rain fall run off and reduce the soil erosion. On the other hand the concave land form concentrate the run off on the bottom site and intensify the soil erosion in that. Therefore the design of field construction should be performed the convex land form.(2) Field institutions such as catch levee, silting weir and grassed waterway-road having a shallow V type section are effective for prevention of top soil erosion. They have a large section for run off water and can cathches much silting soils and doesn't bury in them. Also these are planned and constructed with a less-costed method.(3) Rain fall retaintion in the field increases with the years after reclamation. This increase is due to the enlargement of infiltration in field soil layer and this infiltration increases with the root pores formed by the crop plants and cracks developed by soil drying. Further, the top soil dressing contribute to the increase of rain fall retaintion.2. Glassland(1) Graded land form and institutions are similar to ordinary field and good results are obtained. It can finds neither collapse, erosion nor water pollution during reclamation.(2) The top soil dressing and cultivation are abbreviated for making seedbeds and seeds are pressed with a bulldozer instead of a tractor. But a good yield and quality of grasses can be gotten by soil improvement and fertilizer application.(3) The top soil hardness is investigated according to real state of expreimental divisions in grassland.