Influence of Salt Composition on the Enzymatic Activity of Degraded Soils in the Astrakhan Region

The influence of salt composition on the enzymatic activity of soils of the Astrakhan region: solonchaks (Haplic Solonchaks (Aridic)), brown arid (Endosalic Calcisols) and alluvial sod (Calcic Fluvisols) soils. Ten soil samples taken from the upper soil layer (0-20 cm) from the territory of the Narimanovsky, Trusovsky and Privolzhsky districts of the Astrakhan region were examined. Sulfate and sulfate-chloride types of salinization predominate in the studied soil samples. In the non-saline alluvial sod soil of the Volga region of the Astrakhan region, the maximum integral index of enzymatic activity was found for all enzyme classes (87%), while in a similar soil with an average degree of salinity its value was 1.5 times lower and approached that in Solonchaks. Under soil salinization, the enzymes of the C cycle (invertase, dehydrogenases), N (urease), S (arylsulfatase) and P (phosphatase) showed the greatest sensitivity, and the enzymes of the O cycle (ascorbate oxidase and peroxidase) showed the least sensitivity. The use of enzyme activity in saline soils as a diagnostic indicator is possible considering the type of soil, the chemistry of salinity, and the cationic and anionic composition of the soil.