RELATIONSHIPS BETWEEN THE NATURE OF SOIL ORGANIC MATTER AND ROOT LIGNINS OF GRASSES IN A ZONAL SEQUENCE OF CHERNOZEMIC SOILS

Abstract

Clay–organic complexes, humic substances, and grass roots were separated from the Ah horizons of soils sampled at undisturbed sites in three Chernozemic soil zones from under dominantly single species of grass. Derivative thermograms (DTG) and infrared (IR) absorption spectra of the soil materials and of the lignins of the grass roots were compared. The data indicated that the organic matter (OM) of the Black soils contained fewer aliphatic groups and more carboxyl groups and was more resistant to thermal decomposition than that of the Brown soils; the OM of the Dark Brown soils was intermediate. The root lignins from the same soils showed many of the same zonal variations in the IR and DTG properties as did the soil OM.