To provide a plowland conversion method and an irrigation drainage system in which a farm field which has been used as a rice paddy is used as a dry field.SOLUTION: When a farm field 100 which has been used as a rice paddy is converted into a dry field, ridges 102 are formed in the farm field, and groove-shaped water shielding member 12 extending in a longitudinal direction of the ridge and perforated pipe 14 arranged on the upper side of the water shielding member are constructed inside the ridges. Then, when the farm field is switched from the dry field to the rice paddy, the water shielding member and the perforated pipe are removed from the farm field.SELECTED DRAWING: Figure 2【課題】田畑転換方法および灌漑排水システムに関し、水田として利用していた圃場を畑地として利用する、田畑転換方法および灌漑排水システムを提供する。【解決手段】水田として利用していた圃場100を畑地に転換するとき、圃場に畝102を形成すると共に、その畝の内部に、畝の長手方向に延びる溝状の遮水部材12と遮水部材の上側に配置される有孔管14とを施工する。そして、圃場を畑地から水田に戻すとき、遮水部材および有孔管を圃場から撤去する。【選択図】図2
