CHEMICAL PROPERTIES OF ORGANIC MATTER EXTRACTED FROM A NUMBER OF Ah HORIZONS BY A NUMBER OF METHODS

Abstract

The organic matter of eight Ah horizons, representing four soil Orders, was extracted and purified by a number of procedures, all designed to extract humic acid or high-molecular weight complexes. Organic carbon and total nitrogen contents of the air-dried soils were determined. The humic substances extracted from the soil were analyzed for carbon, nitrogen, total and carboxyl acidity, and ash and a number of its constituents. The nitrogen content and carboxyl acidity of the humic acids as well as the soluble silicon, calcium, and phosphorous content of the ash varied with the method used to extract the humic substances. The extraction of soil organic matter from Ah horizons by chelating resins merits pursuance. Often, high carboxyl acidities, as confirmed by infrared spectra, existed notwithstanding high ash contents. Other criteria, such as nitrogen content of the humic substances, may also have to be considered in this ash–carboxyl acidity relation. The materials extracted from the Lithic Regosol had relatively high calcium contents, low nitrogen and ash contents, and high calcium content of the ash, as compared with the other seven soils, regardless of method. With two methods total acidity was also high.