PROBLEM TO BE SOLVED: To provide a farmland conversion method for converting farmland from paddy field to upland using a water level adjustment system in consideration of soil preparation. SOLUTION: The farmland conversion method of the present invention is a farmland conversion method for converting farmland from paddy fields to upland fields, and is an underdrain pipe which is arranged under the farmland and has a plurality of through holes formed on the outer periphery thereof. , A water level adjusting step of lowering the underground water level and a water level adjusting step are performed after the water level adjusting step by using a water level adjusting system having a water bar connected to the underdrain pipe and adjusting the underground water level using the water head pressure. The step includes an agglomeration step of cultivating the soil of the paddy field and mixing the agglomerating material containing rotaceous acid into the soil of the paddy field to agglomerate the soil of the paddy field. [Selection diagram] FIG. 8【課題】本発明は、土づくりを考慮した水位調整システムを用いての農地を水田から畑地に転換する農地転換方法の提供を目的とする。【解決手段】本発明の農地転換方法は、農地を水田から畑地に転換する農地転換方法であって、前記農地の地下に配置され、外周に複数の貫通孔が形成されている暗渠管、及び、前記暗渠管に連結され、水頭圧を利用して前記地下の水位を調整する水閘を備える水位調整システムを用いて、前記地下の水位を低下させる水位調整工程と、前記水位調整工程の後に行う工程であって、前記水田の土を耕起しながら前記水田の土に腐植酸を含む団粒化材を混入させて、前記水田の土を団粒化させる団粒化工程と、を含む。【選択図】図８
