Abstract
To predict present-day soil distribution in Japan, it is necessary to clarify the effects of landform, land improvement, and land-use changes on soil class because many agricultural fields have experienced anthropogenic activities since the original agricultural soil maps were created. For this purpose, we compared the previous soil profiles of a paddy field in Shiga prefecture with the results of a present-day simple soil profile survey. The results of this survey revealed that Gley lowland soils were distributed in a valley bottom plain, regardless of soil class, before land improvement and associated soil movement due to normal water addition from a nearby forested area. Although there was no relationship between soil classes in the delta landform, the soil class changed after the introduction of a drainage system and subsequent land-use changes. Gley lowland soils that occurred in the delta before land improvement were subsequently altered to other soil classes. Some soils provided good drainage in the delta before the land became a lowland-paddy soil area by paddy soil-forming processes over more than 50 years. In conclusion, although land improvement and land-use changes had a significant impact on the agricultural field surveyed, we are still able to predict modern soil distribution by considering current landforms and past soil conditions.
