Soil structure development in ariake polder soils in relation to iron forms

Abstract
The Ariake Polder area in Saga Plain derived from the marine alluvial of the Ariake Sea is one of the most important rice regions in Japan. Some portions of this area have been under cultivation for the last 400 to 500 years, while other parts were reclaimed as recently as in the last two years. Agriculturally, the soils are generally highly productive as evidenced by the high yield of paddy rice.