Subtype features of humus dynamics in chernozems of the center of the Russian Plain under conditions of long-term agricultural use

Abstract

The long-term dynamics of the humus content and reserves in the forest-steppe and steppe chernozems of the center of the Russian Plain was studied in a series: virgin land - perennial arable land. To the greatest extent, the transformation of the humus profile of chernozems as a result of plowing is manifested in its upper part. The depth of transformation spread reaches approximately 80-90 cm. In the series of subtypes: podzolic - leached - typical - ordinary chernozems, there are differences in the amount of humus lost. Long-term plowing of these soils leads to the humus content decrease. Therefore, real (t/ha) and apparent (%) humus losses in soils during their long- term plowing can differ significantly. The greatest losses of humus were recorded in leached chernozems – 15 t/ha. In podzolic and ordinary chernozems, the loss of humus reserves was approximately the same and amounted to 13 and 14 t/ha, respectively. Typical arable soils, as a rule, contain 15 t/ha fewer humus reserves than virgin soil. The humus level of chernozems varies significantly in the first years of use, then it stabilizes at a fairly high level according to the new regime of matter and energy circulation in agrocenoses. An objective assessment of changes in the main indicators of the humus state of chernozems during their long-term agricultural use should be carried out not by the percentage of humus but by its reserves, taking into account the corresponding values of the equilibrium addition density.