Abstract
While productivity in converted paddy fields in hilly and semi-mountainous areas is important, excess moisture damage due to poor drainage is a serious problem in Japan. The objective of this study was to develop an effective drainage method for farmers, by focusing on the artificial landform transformation history of the fields.The experiment was conducted from 2020 to 2022 at fields in a hilly and semi-mountainous area in Higashi-Hiroshima, Hiroshima Prefecture, using a rice husk underdrain construction machine and a bullet underdrain construction machine for upland farming in a paddy field rotation. A construction map was created using past aerial photographs, and the underdrain was settled in the direction connecting the leveled and reclaimed areas. Subsidence of the ground surface was observed at the reclaimed area, and water was found to be collected in the reclaimed area. In 2022, the soybean seedlings and yields were improved by installing a drainage outlet in the reclaimed areas and by connecting the leveled and reclaimed areas through underdrains. Taking into consideration the location of the drainage outlet, a significant increase in the seed yield was observed. These results suggest that in hilly and semi-mountainous areas, the effect of drainage methods can be enhanced by focusing on the artificial developmental history of the fields.
