Polysaccharide constituents in fulvic and humic acids extracted from soil

Abstract

Soil humic materials extracted from three dissimilar soil profiles were studied by infra-red spectroscopy. Carbohydrates in the form of polysaccharides were present in close relation or as constituent components in the fulvic and hymatomelanic acids encountered in both the surface and deeper layers of the soils examined. The fractionation procedure that yielded polysaccharide from hymatomelanic acid failed to do so when used on humic acid. At least two kinds of polysaccharides were encountered - those from fulvic acid, with a single peak at 1,650 cm −1, and those from hymatomelanic acid, with twin peaks at 1,650 cm −1 and 1,400 cm −1. Fulvic acid in acid brown forest soil formed under pine vegetation had a stronger phenolic or lignoid character and a weaker polysaccharide character than did fulvic acid in a chestnut and an alluvial soil formed under grass vegetation. This difference was especially pronounced in the surface soil, but disappeared in the subsoil. The infra-red spectra of polysaccharides in the hymatomelanic acids of the surface layers of the three soils were, however, surprisingly similar.