Abstract
In three 30 a paddy fields of Gravelly Gley Upland Soils, main underdrains and the pipes for draining the surface water and penetration water were constructed. As the soils of this paddy field contained adequate amount of sand and gravel, numbers of soil cracks and water permeabilities of soils were increased during cultivating soybean, and soybean growth and yield were good. Both soil drainage and field maturing process in this Gravelly Gley Upland Soil had advanced to about 30 cm depth. In 30 a paddy field of Fine-Textured Gley Upland Soil, in addition to the construction of main of 20 cm in depth were dug with 5 m interval to accelerate the drainage of surface water. Because the soil had high clay content (LiC), and massive layers, the water permeability and formation of soil cracks were not improved, which caused injuries to the planted barley owing to the excess moisture. It can thus be concluded that the conversion of paddy field of Fine-textured Gley Upland Soil to matured upland field was considerably difficult without intensive drainage system.
