The changes in the structural state of a typical chernozem (Haplic Chernozem) under various tillage practices (plowing, combined tillage, surface tillage, No-till) in the central chernozemic region (Kursk oblast) were studied. The macrostructural state of the soil was determined by the dry and wet sieving methods. Changes in the weighted average diameter of dry and water-stable aggregates, their entropy of distribution, and the weighted average diameters of the aggregates, which were destroyed by the harder impact and the particles to which air-dry aggregates were broken down were determined; the content of water-stable aggregates and their weighted average diameter were also determined. An increase in the weighted average diameter of the aggregates of dry and wet sieving under minimized primary tillage was found. Thus, plowing to the depth of 20-22 cm led to a decrease in the weighted average diameter of aggregates, which were destroyed by the harder impact, and the particles to which these aggregates were broken down. At the same time, tillage minimization led to an increase in the weighted average diameter of water-stable aggregates. The entropy of the aggregate-size distribution for both dry and wet sieving depended on the season and on the tillage depth. The relationship between the sum of water-stable aggregates according to Savvinov and the index of aggregate susceptibility to destruction upon wetting were analyzed. Regardless of the tillage practice and considered layer, the soil was characterized by the medium-quality structure (class III) before crop sowing and during the harvesting. Direct sowing technology improved the structural state in the topmost 10 cm to the good quality (class IV). The results of this study can be used to evaluate resource-saving methods of tillage.
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