Features of modern genesis of the Ishim steppe watershed plain soils

Abstract

The genesis main directions of the Ishim steppe watershed plain soils depending on their economic use (arable land, forest belt, abandoned land) during the 1950s – 2020s were revealed. Within the studied region, soils were diagnosed on lands of different use. It is shown that the regional morphogenetic feature of all watershed plain soils is the tonguing of the humus horizon, which is reflected in their classification status by the allocation of a dark-tonguic subtype of the soils. Differentiation of the agrodarkhumus horizon into two subhorizons under the influence of plane-cutting processing was revealed in the agrozem, prevailing by area. The manifestation of postagrogenic transformation of soils occurring under forest belts and under deposits with herbaceous vegetation is determined. Postagrogenic soils are characterized by a granular structure, higher reserves of humus and total nitrogen in a layer of 0–20 cm compared to agrozems. In the soil of the forest belt, a coarse-humus neo-horizon was formed, which is not typical of steppe soils. The soil under abandoned for a long time grassland has signs of dark humus horizon progradation to a state close to a virgin one. The additional surface moistening of micro-subsidence soils causes them to have a higher humus content and its reserves in the 0–100 cm layer, deeper leaching of carbonates, the formation of a clay-illuvial horizon in the carbonate-free zone and prevents the formation of a gypsum horizon. The groundwater level raising in the modern period, which is a consequence of the mass plowing and functioning of impenetrable protective forest belts in the study area, caused the appearance of neo-hydromorphism in watershed plain soils and the formation of quasi-clay subtypes. The results indicate the regional specificity of the genetic properties of the Ishim steppe watershed plain soils that distinguish them from their European counterparts, as well as the influence of agrogenic transformation as an anthropogenic factor on them. This influence is reflected in the morphology of soils, their humus state, the nature of the carbonate and gypsum profiles, the processes of halogenesis in them and the variety of salt profiles.