Abstract
The humus contents and the Ch/Cf ratios of fifteen Humic Allophane soils were very high and the humus composition was characterized by the predominance of fraction 1 and low contents of fraction 2 and humins. The Ch/Cf ratios of Humic Allophane soils have certain geographical regularities. In Japan the ratios generally increase from the north to the south. Though the former contains a considerable amount of amorphous aluminosilicates dissolved by the Tamm's reagent, Altered Humic Allophane soils should be distinguished from Humic Allophane soils by the predominance of 14Å minerals and kaolin minerals. The Ch/Cf ratios of nine Altered Humic Allophane soils are higher than those of Humic Allophane soils, but the aromatic nature of the humic acids is almost the same as that of Humic Allophane soils. If Altered Humic Allophane soils were of the hydromorphic origin, their humic acids would not have such a high degree of aromaticity. The humic acids of normal and Altered Humic Allophane soils can be distinshished from those of Red-Yellow soils by their high Ch/Cf ratios and aromatic nature. Therefore, the forming process of the humus of Altered Humic Allophane soils is different from that of geographically associated Red-Yellow soils, but closely resembles that of Humic Allophane soils. This is the reason why Altered Humic Allophane soils should be regarded as a subtype of Humic Allophane soils.
