Influence of irrigated mineralized waters on properties of ordinary chernozem in the conditions of Prysamaria Dniprovske

Abstract

Irrigation of lands in arid climates helps to solve the problem of water deficit of soils in order to increase their fertility. However, under the influence of mineralized waters used for irrigation, there is a degradation of chemical, physico-chemical, water-physical and physical properties of soils. Soil monitoring is one of the effective mechanisms that allowsassessing the current state of soils and predicting the negative consequences of economic activity in the future. The area where the research was conducted is in the zone of insufficient moisture where there is an annual deficit of water balance of soils. Irrigation in the studied areas began in the mid-70s of the last century and lasted until 1992. The waters of the Samara River were used for this purpose. The total mineralization of water during the growing season reaches 3515 mg/dm3. It is possible to estimate the degree of transformation of soils that have been under the influence of irrigation waters for a long time in relation to the indicators of virgin soils. The zonal soils of the research area are CalcicChernozems. The analysis of macromorphological indicators showed that irrigation soils differ from the reference ones by the thickness of the organogenic horizon, density and structure. The results of the analysis of the aqueous extract of the reference soils show the absence of salinization with water-soluble salts. Their content varies in the range from 0.051 to 0.078 %. A maximum of one salt is observed in the soil profile, namely in the transitional horizon at a depth of 45–63 cm. Below this depth, the content of water-soluble salts progressively decreases. The total content and distribution of water-soluble salts in the soil profile of irrigated soils has some differences from the reference soils. In the upper part of the humus horizon, the total amount of water-soluble salts is smaller, which can be attributed to the effects of machining and better aeration, as well as the intensive removal of their vegetation. Below these horizons, the amount of water-soluble salts progressively increases and reaches a maximum in the soil-forming rock. The nature of the distribution in the soil profile and the total amount of salts isnot typical for Calcic Chernozems and ismore similar to those of Gleyic Calcic Chernozems. The maximum amount of water-soluble salts is concentrated in the parent rock. Their percentage indicates the absence of salinity in both studied soils. But guided by the method of calculating the content of toxic water-soluble salts in the soil, in the reference soils, this figure reaches 0.21 t/ha in a meter layer of soil, and in irrigation 0.42 t/ha. The results of studies of physicochemical parameters show that a higher content of metabolic calcium is characteristic of the reference soils, and its distribution in the soils along the profile of both options is relatively similar. In contrast, the distribution of exchangeable magnesium in the soil profile varies greatly, especially in the reference soils. In irrigated soils, the ratio of exchangeable calcium to magnesium is more stable and varies in the range from 4.2 to 7.9, which may be the result of prolonged irrigation. According to the obtained physicochemical parameters, irrigation soils have weak salinity in the lower part of the transition horizon. This indicator, together with the ratio of exchangeable calcium to magnesium, indicates eluvial-illuvial processes that for some time contributed to the redistribution in the soil profile of both water-soluble salts and exchangeable cations. Evaluation of the degree of salinity of soils showed the absence of salinization in the reference soils, as well as in the upper part of the humus horizons of irrigated soils. Given the buffering of irrigated soils, weak salinity is present only in the upper part of the transition horizon.