Evaluation of the Physical and Chemical Properties of Southern Chernozem Under Conditions of Stationary Crop Rotation and Fallow State

Purpose: to provide a comparative assessment of the physico-chemical properties of southern chernozem under stationary crop rotation and fallow state in the steppe zone of the north-western Azov region and to determine the nature of their changes on different agricultural lands. Materials and methods. To assess the physico-chemical properties of southern chernozem in the 0–30 and 30–60 cm soil layers, samples were collected from arable fields (bare fallow, winter wheat) and a 15-year-old fallow, followed by agrochemical analysis. Results. A decrease in the content of exchangeable calcium in the soil after winter wheat and bare fallow and its significant increase by 18–20 % on fallow lands were found. The cation exchange capacity of agricultural soils is characterized as average (18–28 mmol/100 g). The calcium content in the soil of crop rotation fields decreases compared to fallow land, and in the arable layer it is 73.7–75.0 %. The degree of base saturation on fallow lands was 94.2 %, on crop rotation field soils it was 93.9 % for bare fallow and 91.8 % for winter wheat. The mass fraction of toxic salts in fields involved in crop rotation confirms the absence of salinization; their content does not exceed 0.039 %. On fallow lands, their decrease by 40 % (does not exceed 0.023 %) was noted. The conducted studies confirm that, the analyzed soils are classified as non-saline and non-alkaline on the basis on the amount of solid residue (0.11–0.14 %), electrical conductivity (0.036–0.094 mS/cm), and the cation composition of the aqueous extract. Conclusions. Under conditions of insufficient and uneven moisture and high temperatures, leaving the soils fallow facilitates their restoration through natural phytoreclamation. The calcium content increases, creating favorable conditions for increasing the soil's base saturation and leading to the gradual restoration of the natural structure of southern chernozems.