Özet:

Rice growing, in contrast to other agricultural crops, significantly changes the main soil processes, including water-air, nutrient, oxidation-reduction and salt regimes. Changes in the structure of crop rotation, growing technologies of agricultural crops and deterioration of the technical state of the rice irrigation system can lead to the development of processes of secondary salinization and solonetzification of soils, decrease of their fertility. To determine the influence of long-term rice growing on the salt composition of the main soil types of irrigated rice crop rotations, the models of qualitative composition of hypothetical salts for the soil layer up to 2 m with the comparison of salt composition before sowing (spring) and after harvesting of agricultural crops (autumn) are constructed. The model of qualitative composition of hypothetical salts of dark chestnut soil shows insignificant differences between the salt composition in spring and autumn, a decrease in the number of non-toxic salts and an increase of the part of toxic salts in the soil layer deeper than 80 cm in autumn. The salinization type of the all investigated layers of dark chestnut solonetzic soil is sulfate, calcium-sodium. The modelling of the salt composition of meadow-chestnut solonetzic soil indicates positive changes after growing of agricultural crops in connection with the appearance of non-toxic salt of calcium sulfate in the soil layer below 1 m. The type of salinization of meadow-chestnut solonetz soil is sulphate, calcium-sodium, and magnesium-sodium from a depth of 60 cm. The qualitative composition of hypothetical salts of meadow solonetz differs to the worst from other types of soils on connection with the presence of hydrocarbonates and sodium carbonates at a depth of 1 m. Comparison of the salt composition of the profile of meadow solonetz in spring and autumn indicates the meliorative function of rice growing. The salinization type of soil layers 0–100 cm is sulfate, 100–200 cm – sodic-sulfate, calcium-sodium, but in the autumn is magnesium-sodium. By the study it is shown that during the operation of rice irrigation system in the designed mode, using crop rotation and rice content not more than 50%, the salt regime of soils, namely, the qualitative composition of hypothetical salts up to a depth of 2 m is constant, without toxic salinization and secondary solonetzification processes. Rice irrigation systems, which are operated for a long time in the designed mode, under condition of observance of crop rotation and technologies for growing of rice and accompanying agricultural crops, are characterized by consistently good agroаmeliorative status. This is confirmed by yield data of rice (6.34–6.67 t/ha) and accompanying agricultural crops (soybeans 2.15–2.97 t/ha, spring barley 3.05–3.49 t/ha, winter wheat 4.85–4.90 t/ha)

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