Infrared spectra of humic acids from soils formed under grass or trees

Abstract

The infrared absorption spectra of various humic acids have been examined to establish whether the 2, 500−1, 800 cm −1 spectral region may be used to distinguish between soils formed under grass or under trees or to separate Chernozemic from Podzolic organic matter. It appears evident that the spectral slope or configuration in this region is related to the molecular weight of the material examined and to the vegetation under which the humic substances are formed or transformed. The change from Podzolic to Chernozemic organic matter occurred within a few years. The change in the opposite direction took a number of years, and even then Podzolic characteristics of the organic matter as measured by the configuration of the spectral region between 2, 500 and 1, 800 cm −1 first became evident in the Bt horizon. The same results were obtained under poplar as well as under coniferous trees.