Prevention of degradation processes of soils irrigated with mineralized water through plastering

Abstract

The long-term irrigation of extensive areas in the steppe zone of Ukraine using low-quality and mineralized water has caused degradation processes associated with soil salinization. To mitigate or alleviate these processes, researchers investigated the potential of chemical reclamation through the application of phosphogypsum. The study took place in the northern Steppe of Ukraine near the village of Oleksandrivka, Dnipro district, Dnipropetrovsk region. Over many years, field experiments were conducted, introducing phosphogypsum as a chemical meliorant. The experimental design included the application of phosphogypsum at rates of 1.4, 3.0, and 6.0 t/ha during different periods of the year. Standardized research methods were used for sampling, laboratory analysis, and processing of the results. The research identified a high salt content (0.35-0.48%) in the arable soil layer, signs of salinization (exchangeable sodium content of 3.64%), and unsatisfactory physical condition of the soil in the research areas. The application of phosphogypsum led to an increase in sulfate anions, as observed in the soil's sulfate chemistry, while the control areas exhibited a soda-sulfate type of salinity. The pH level of the water extract remained within neutral values throughout the years of the study. Positive changes were observed regarding the degree of soil salinity. Specifically, the application of phosphogypsum at rates of 3 and 6 t/ha in irrigated areas resulted in a change from moderate to slightly saline salinity levels. The research also demonstrated a positive effect on the sodium-adsorption ratio, particularly when phosphogypsum was applied during irrigation in the third year. The sodium-adsorption ratio decreased by 69% compared to the control options, indicating a better ameliorative effect of phosphogypsum during irrigation. Under the conditions of using water of class II quality for irrigation, the optimal application of phosphogypsum was found to be at doses of 3 t/ha for spring cultivation and 6 t/ha for the main cultivation in autumn. These application rates effectively reduced the degree of soil salinity and improved the ecological and meliorational conditions of the irrigated area