INFLUENCE OF DIGESTATE ON THE AGROCHEMICAL COMPOSITION OF SOIL AND CARBON ACCUMULATION IN IT

The article presents the results of studying the influence of digestate on soil fertility indicators and organic carbon accumulation in it. The research was conducted during 2019–2024 under the conditions of LLC "Organic-D" on gray forest soils of light loamy mechanical composition. The results of the conducted studies established that the application of digestate, obtained by 14-day fermentation of pig manure in a biogas plant, which has an alkaline solution reaction, a significant amount of macro- and micronutrients, and beneficial microorganisms, positively affects the indicators of carbon accumulation in the soil from 1.03% to 1.50%, reduces acidity (exchangeable pH) from 4.68 to 5.7, and increases the content of macroelements in the soil: ammonium nitrogen (NH₄⁺) from 14.13 mg/kg in the control to 41.20 mg/kg in the variant with biennial digestate application; nitrate nitrogen (NO₃⁻) from 1.37 mg/kg to 47.50 mg/kg; ammonium-nitrate nitrogen (NH₄⁺+NO₃⁻) from 15.50 mg/kg to 88.70 mg/kg; phosphorus (P2O5) from 75.77 mg/kg to 100.70 mg/kg; potassium (K2O) from 103.33 mg/kg to 230.40 mg/kg; sulfur (S) from 2.4 mg/kg to 9.0 mg/kg. Additionally, the content of micronutrients increased: copper (Cu) to 0.13 mg/kg, zinc (Zn) to 1.32 mg/kg, manganese (Mn) to 7.16 mg/kg. Overall, in the experiment, the application of digestate ensured an increase in organic carbon content by 0.148% compared to the control variant (without digestate application). The cation exchange capacity was highest in the variant with three-time digestate application: basal fertilization (60 t/ha), pre-sowing application (60 t/ha), and top dressing (60 t/ha), reaching 176 mmol+/kg of soil, while in the control variant, it was 147 mmol+/kg of soil. The application of digestate also positively influenced the content of physical clay in the soil. Specifically, in the variant with three-time digestate application: basal fertilization (60 t/ha), pre-sowing application (60 t/ha), and top dressing (60 t/ha), the clay fraction content was 19%, compared to 16% in the control variant. The highest organic carbon content in the arable soil layer was recorded in the variant with three-time digestate application: basal fertilization (60 t/ha), pre-sowing application (60 t/ha), and top dressing (60 t/ha), reaching 173.25 t/ha. In comparison, the organic carbon stock in the arable soil layer of the control variant was 138.38 t/ha, resulting in an increase of 34.88 t/ha.