Carbonaceous materials as a possible source of soil humus

Abstract

Based on the optical properties, Kumada et al. (I) proposed to classify soil humic acids into A. B, Rp and P types. Among them, A type is characterized by stronger light absorption and lower inclination of the absorption curve, compared with other types of humic acids, and predominates in andosols (volcanic ash soils in Japan), chernozems, grumusols and rendzinas. The absorption curve in the UV and visible region of P type humic acids is characterized by the presence of absorption bands at 615, 570, 450 and 280 nm, and this type distributes widely in podzols, brown forest soils ID Japan and other soils. In 1966, it was found however. that humic acids obtained from the II and A horizons of a podzol in the Tyrebagger forest near Aberdeen, Scotland, belonged to A type, and the same type of humic acid was recovered from charcoal (charred wood) buried there (2). Among the twelve samples (A and B horizons) of podzols collected during the Tour 12 of the 11th lCSS held in Canada in 1979, in ten samples and in the remaining two samples, P type and A type humic aCids could be identified, respectivly. Charcoal fragments were observed in these two samples after treatment with hydrogen peroxide (3). These findings strongly suggest that such carbonaceous materials as charcoal and cinder are a possible source of A type humic acid.