抄録
In the degrated paddy soils, the free iron oxides in the fallow soils were leached during the waterlodged periods, and were accumulated at the lower layers. In this paper the authors investigated the leaching mechanisms of the free iron oxides. The results are summerised as follows. In the reductive layers of the paddy soils, H_2S (S") are formed from the sulphates and organic substances which contain the sulpher, and F^<・・> are formed from the free iron oxides. In the case of the normal paddy soils F^<・・> predominate over S", But in the case of the degrated paddy soils S" predominate over F^<・・>, so that the formed FeS-gel change to the sol and then with the percolate-water the FeS-sol are leached from the fallow soils to the lower layers.
