Аңдатпа
Liman irrigation lands in the arid zone of West Kazakhstan are highly dependent on periodic flood irrigation and are subject to degradation due to secondary salinization and deterioration of soil agrochemical properties. Improving their productivity requires the application of integrated reclamation measures, including regulated flooding and chemical amelioration. The aim of this study was to evaluate the effects of gypsum and elemental sulfur on soil agrochemical properties and vegetation productivity under liman irrigation conditions. The study was conducted in 2024-2025 within the Ural–Kushum irrigation and water distribution system (West Kazakhstan region). Field experiments included the application of gypsum at rates of 6 and 12 t ha⁻¹ and elemental sulfur at 3 and 6 t ha⁻¹. Soil parameters (pH, humus content, nitrate nitrogen, available phosphorus and potassium, sulfate sulfur, and cation–anion composition) as well as vegetation productivity were assessed. The results showed that the control soils were characterized by an alkaline reaction (pH 8.2-8.5), moderate salinity, and limited nutrient availability. The application of chemical amendments led to a reduction in soil alkalinity to pH 7.7-7.9, a decrease in total salinity, and an improvement in the ionic composition of the soil solution due to the replacement of exchangeable sodium by calcium (under gypsum application) and microbial oxidation of sulfur. The most pronounced effects were observed under gypsum application at 12 t ha⁻¹ and elemental sulfur at 6 t ha⁻¹. In these treatments, available phosphorus increased to 41.2 and 35.2 mg kg⁻¹, nitrate nitrogen reached 8.25 and 8.24 mg kg⁻¹, respectively, and humus content increased to 2.38–2.45%. These improvements were accompanied by increased grassland productivity and a higher proportion of grass species in the vegetation structure. Thus, the combined use of regulated flooding and chemical amelioration effectively optimizes soil agrochemical properties and enhances the productivity of liman irrigation agrocenoses. The most effective treatments were gypsum at 12 t ha⁻¹ and elemental sulfur at 6 t ha⁻¹.