THERMODYNAMIC STABILITY FIELDS OF HUMUS, MICROFLORA AND PLANTS

A method to determine Gibbs free energies of soil organic compounds: f ulvic acids, humic acids, humin, microflora and plants, is presented. The thermodynamic stability fields are a function of capillary water a ctivity ([H2O]), chemical composition of soil solution, as well as of carbon dioxide, f(CO2), and oxygen, f(O-2), fugacities in the soil atm osphere. The results obtained agree perfectly with what is generally k nown about organic matter in soils. The bases of a thermodynamic treat ment of the soil-plant-water systems is thus established where inert a nd living organic matter clearly are closely associated.