Structural state of chernozems of Forest-Steppe zone at agrogenic impact

Abstract

Goal. To determine the main regularities of the transformation of the structural state of chernozems of the Forest-Steppe zone under conditions of long-term agrogene transformation. Methods. Field and laboratory experiment (dry structural dispersion of soil). Statistical-analytical method of factor analysis (principal component method), cluster analysis, non-parametric methods of analysis of the obtained data of the structural state. Results. They fixed the following regularities at the increase of agro- and technogenic load on the chernozem: fractions of structural parts in size of >7 mm were formed of the greater degree, and to a lesser extent there were formed fractions in size of <0.25 mm. At the same time, they determined a decrease in the number of the most valuable in agronomic understanding of fraction in size of 3.0–0.5 mm. That process is much more evident at the systematic plowing. The use of subsurface cultivation contributed to the restoration of soil structure and the formation of separate intermediate fractions in size of 7–5 mm and 5–3 mm, and a slight increase in the number of fractions in size of 3–0.5 mm. It also promoted the destruction of big fractions, with a gradual increase in the number of more valuable fractions (7–5 mm and 5–3 mm), which led to a minor increase in the density structure of the 0–30 cm soil layer in the first 3–5 years. Loosening started at the increase of the content of structural units in size of 5–3 mm with the further consolidation of the soil structure around the formation of the structural units of size 3–0.5 mm, which caused the decrease in the content of structural units in size of <0.25 mm. Conclusions. So, the size fraction of 10–7 mm is an important characteristic of cultivated chernozems of Forest-Steppe, which can determine the formation of the chernozem in agrocenoses under the influence of agrogenic load. General regularity was fixed: regardless of the status of the chernozem the share of units in size of 3–0.5 mm in the amount of agronomically valuable (7–0.25 mm) units, regardless of their number, was 51–54%, and increased agrogenic load accelerated the formation of big fractions (>7 mm) up to 30%, of agronomically invaluable units — to 35.6%, the share of structural units in size of <0.25 mm made 6–10%.