PHYSIC-CHEMICAL PROPERTIES OF TYPICAL CHERNOZEMS OF PRYDNISTERSK PODILLYA

Abstract

This article analyzes the physic-chemical properties of typical chernozems. According to the methods, a laboratory study was performed. Physic-chemical parameters that are typodiagnostic for subfacial classification division of typical chernozems of the Prydnistersk Podillya are determined. Typical chernozems of the Prydnistersk Podillya are low-humus (2.78–3.98%). With depth, the humus content decreases by an average of 0.2% for every 10 cm, which indicates a uniformly accumulative type of distribution of organic matter in the profile of chernozems. In the same direction, humus reserves are declining. There is a spatial correlation between the humus content and the amount of physical clay in the fine soil.
 Humic acids predominate in the humus to a depth of 90–100 cm (Sgk: Sfk is 1.12–1.78). The general tendency of relative “fulvatization” of the arable layer as a result of its agrotechnical depletion is noticed. In relation to SGC to total organic C, chernozems of the study area are characterized by a high and very high degree of humification of organic matter. It is highest (62–70%) in the soils of the key section “Humentsi”, decreasing to 52–62% and 43–63% in the western direction.
 The humic acids of typical chernozems are dominated by calcium humates (GK-2). The largest number of them (29–35%) is concentrated on the contact boundary of humus and carbonate profiles. The convex nature of the distribution curves of the fraction of 2 humic acids and a sharp decrease in its content deeper than 100 cm, indicates their high migration capacity and the possibility of significant deposition of only a significant excess of calcium carbonates. The intensity of migration processes of the GK-2 fraction decreases in the direction of increasing the stiffness of hydrothermal conditions, due to the pulling of carboxylic acid salts closer to the soil surface, supersaturation of the solution with calcium bicarbonate, and as a consequence, increasing the total alkalinity in the humus horizon.
 The capacity of cation exchange (ECO) of typical chernozems is quite high (29–32 mmol-eq / 100 g of soil) with the dominance of calcium and magnesium cations in the composition of the soil-absorbing complex (GVC). There is a general tendency to increase these indicators in chernozems with low values ​​of SCC of the territory.
 The pH of the aqueous extract of typical chernozems of the Prydnistersk Podillya increases with depth from weakly acidic in the arable horizon to weakly and medium-alkaline within the carbonate profile. The reasons for such changes in the increase with the depth of the concentration of Ca2 + bicarbonates, which in their dissociation leads to an increase in the amount of hydroxyl ion and increase the alkalinity of the soil.
 The carbonate profile of typical chernozems is dominated by migratory forms of carbonate neoplasms - mold, carbonate plaque, veins. The vertical curve of carbonate content has an eluvial-illuvial type of profile structure. The content and reserves of carbonates in the 1.5-meter layer of typical chernozems increase from the west (434–714 t / ha) to the east (979–1847 t / ha).
 Key words: physic-chemical properties, typical chernozems, humic horizon, humic acids, carbonate profile.