CHANGES OF SOIL ORGANIC MATTER UNDER ECOLOGICAL AND CONVENTIONAL FARMING SYSTEMS

Abstract

The paper presents changes in the organic matter of the arable layer (0-25 cm) of soil from crop rotations under the conventional and the ecological farming system. Organic matter quality was estimated based on the chemical fractionation of humus compounds. The susceptibility to oxidation of soil organic matter with potassium permanganate (KMnO4) solutions was also analyzed. Changes in humus fractions caused by crop succession were generally slight, probably due to a short period of time that passed from the moment of converting two crop rotations to the ecological system. A higher content of free humic acids and the fraction of carbon most prone to oxidation in soil from conventional crop rotation may be related to the kind of plant remains and the application of mineral fertilizers. A higher content of humins and a lower content of free humic acids in soil from ecological crop rotations may indicate more favourable conditions for the formation of permanent mineral-humus bonds.