Features of structural-aggregate condition of forest chernozems in Hlyboky ravine
Authors: Gorban V. A. , Strygina T. A. , Mandrygelia M. V. 
Published: February 2020

As it is known, the structure of the soil, as well as the qualitative characteristics of its units (size, water resistance, mechanical stability) is largely dependent on the granulometric structure, the availability of sufficient organic matter, vigorous activity of soil microorganisms and mesofauna, development of root systems of plants. The formation of soil structure is a complex physical-chemical process, which results in the adhesion of soil particle-size fractions of humic substances with a corresponding impact of absorbed cations. Therefore, the shape of the structural units can serve as a diagnostic feature that reflects the genetic features and the natural fertility of the soil. Soil structure is a dynamic property and may be changed under the influence of agricultural use and environmental factors. The stability of soils to human impacts depends on their genetic characteristics, factors and soil conditions. In particular, the greatest impact on the structural state of the soil creates a progressive dehumufication. At present the main features of the research focuses on the establishment of a structural condition of chernozems, used in agriculture, while at the same time, structural and aggregate state of chernozems under forest vegetation remains little explored. Accordingly, the aim of our work is to establish the characteristics of the structural condition of forest chernozems that formed in a ravine oak steppe zone of Ukraine. The object of study is based on the soil of Hlyboky Ravine, which is located near the village Andriyivka (Novomoskovsk district, Dnipropetrovsk region). Soil samples were collected in a 5 test areas: the first test area is located on the steppe virgin soil between the field and marge a northern slope, the second – in the middle third of the northern slope, the third – on the flat areas of the thalweg, the fourth – in the middle third of the slope of southern exposure, the fifth – on virgin steppe between the field and marge slope of southern exposure. The research was carried out by sieve method in the modification of N. I. Savvinov. As a result of the investigations it was found that the optimal aggregate state characterized by the surface horizons of the soils, which are dominated by the fraction size of 2–1 and 3–2 mm. The maximum content of agronomically valuable fractions revealed in the horizon H1el southern exposure, in which the structural factor is 30.2 %. The most favorable conditions for the formation of water-resistant structures are typical for the northern and southern exposure of the Ravine. The least favorable conditions for the formation of water-resistant aggregates different northern edge. Minimum variability in terms of structure coefficient among the studied soils characteristic of the soil and the northern edge of northern exposure, and the maximum – for the southern exposure of soil. The most important soil factors which determine the peculiarities of structural-aggregate state of the soils are the eluvial-illuvial processes. Forest chernozems have a very good structural and aggregate state.