Features of the soil absorption complex of leached chernozem during sunflower cultivation in a grain-grass-tilled crop rotation

The purpose of the research is to provide a comparative assessment of the condition of the soil absorption complex of leached chernozem during the cultivation of field crops in a graingrasstilled crop rotation using various intensification technologies: extensive, pesticidefree, environmentally sound, and intensive. The research was conducted in 2020–2025 in the longterm field experiment, traditional methods of soil research were used. It has been established that the intensification of agronomic technologies for growing solid crops (alfalfa, winter wheat, and barley) increased the amount of exchangeable bases in the 0–60 cm layer of leached chernozem by 5.6–6.1%, while decreasing hydrolytic acidity by 7.3–23.4% and active acidity by 2.6–3.9%, relative to the control variant (extensive technology). The intensification of sunflower cultivation technologies increased hydrolytic acidity by 9.3–13.3%, compared to the control. A plowing system with deep periodic loosening of the top 20 cm of soil during sunflower cultivation increased exchangeable bases by 5.7%, decreased hydrolytic acidity by 8.9%, and decreased active acidity by 3.2%. There were no significant differences in the physical and chemical properties of the lower layers depending on the soil treatment system. The negative impact of intensified cultivation technologies on the physical and chemical properties of soil under sunflower was most evident in the 0– 20 and 20–40 cm layers: the sum of exchangeable bases decreased by 4.7%, while the levels of hydrolytic and active acidity increased by 28.0–42.6% and 2.4%, respectively, relative to the control (extensive technology). No significant differences in the physical and chemical properties of the soil were found between the alternative technologies in the 40–60 cm layer. A negative tendency towards a decrease in the degree of saturation of the soil absorbing complex of leached chernozem with bases, especially when using intensive sunflower cultivation technologies.