抄録
In hilly and mountainous areas, many terrace paddy fields have been abandoned due to lack of the successor to the farmer, difficulty of irrigation and so on. To clarify the changes of the soils after abandoned, the terrace paddy fields that were 3,12 and 20 years after farmers give up cultivation were investigated. The neighboring cultivated paddy fields, as the controls, were also investigated in Ohshima village, Niigata prefecture. The soil three years after abandoned had little differences in soil morphology and property compared with the control. In the cultivated paddy fields, the soils were classified into Gley or Gray Upland soils. On the well-drained sites (dominated by Miscanthus sinensis), the soils 12 and 20 years after abandonment had been desiccated and classified into Brown Forest soils. The surface (plow) and subsurface (plowsole) layers of these soils had changes in soil color from reduced gley or gray to oxidized brown and had weakly developed granular structure. In contrast, the soils 12 and 20 years after abandoned on the poorly drained sites (dominated by Phragmites communis) were classified into the same taxa as the controls. Basic intake rate, hydraulic conductivity and macro pore were increased, and exchangeable bases were decreased with the years after abandoned in the surface and subsurface layers of the soils on the welldrained sites. There, however, were not significant differences in these properties of the soils on
the poorly drained sites. After abandoned, soil morphological features and physical properties were remarkably changed on the well-drained sites. The changes of the soils have been influenced by microtopography
and drainage conditions.
