Purpose: to reveal the features of changes in the reclamative state and soil fertility of the lands in the southern Russia by regular irrigation and in the post-reclamation period. Discussion. The reasons for raising the water table (GWL) by regular irrigation are considered: the location of systems in the floodplains of rivers or on terraces I and II, the design of large irrigation plots with an area of about 1000 hectares on irrigation systems, the design and construction of canals and an irrigation network in an earthen channel etc. The main factors influencing the deterioration of the reclamative state and the soil fertility decrease of irrigated land (secondary salinization, alkalinization, waterlogging, overconsolidation, dehumification, etc.) are natural and technogenic factors. Natural ones are climate, geological structure, geomorphological conditions, relief, natural drainage of lands, geochemical and hy-drogeological conditions, types and properties of soils (filtration, etc.), their natural salinity and alkalinity, fertility, etc. Technogenic ones are the efficiency of irrigation systems and their water supply, irrigation methods and technique, irrigation regime, irrigation map planning, types and parameters of drainage systems, quality of surface and drainage waters used for irrigation, technical level of operation of irrigation and drainage systems. Conclusions. The decrease in water load in the post-reclamation period, in the presence of natural and artificial drainage contributed to a decrease of water table and partially secondary salinization, alkalinization, while the soils do not reach the background levels in general. During the reconstruction and construction of new irrigation systems, the complexity and sequence of the measures taken to prevent the increase in GWL, salinization and alkalinization of soils should be observed.

Purpose: to determine the impact of phosphogypsum rates in combination with organic matter on the properties of integrated cover soils, their productivity, and also to substantiate the economic feasibility of their application for chemical reclamation during irrigation. Materials and methods. The studies were carried out in the Martynovsky district Rostov region for 4 years on the integrated cover soils according to the scheme of the experiment, including the application of phosphogypsum (Ph) and organic matter (OM) at certain rates. The studies were carried out according to generally accepted methods. Results. It has been stated that the phosphogypsum application at 10 t/ha rate contributed to the southern chernozem desalination up to 3 % sodium from the total soil-absorbing complex and an calcium and magnesium increase to the optimal parameters for this soil. On the solonetz, the content of exchangeable sodium decreased to 9–8 % in the variants with 10 t/ha Ph rate. In the variant with 5 t/ha Ph rate, the process of soil salinization proceeded somewhat more slowly, which is associated with an insufficient ameliorant rate for the solonetz. The accumulation of humus to the greatest extent was observed in the variant 10 t/ha Ph + 40 t/ha OM. After 4 years, it amounted to 0.24 % on the southern chernozem, and 0.19 % on the solonetz. Both soils included in the complex decompacted, and in the better option, the southern chernozem density was 1.17 t/m³, and on the solonetz – 1.20 t/m³. The soil properties improvement contributed to the increase in productivity. By the 4th year of the aftereffect of ameliorants, it increased by 73–85 % on the southern chernozem and by 69–79 % on solonetz compared with the control. The average productivity for 4 years of research on the southern chernozem ranged from 7.18 (5 t/ha Ph + 40 t/ha OM) to 8.03 t grain units/ha (10 t/ha Ph + 40 t/ha OM), and in the control 4.82 t grain units/ha. On the solonetz, respectively, it increased from 6.03 to 6.93 t grain units/ha, in the control – 4.30 t grain units/ha. Conclusions: the application of phosphogypsum with organic matter provides both reclamative and economic effect on solonetz integrated cover soils.

Purpose: to assess the ecological and reclamation state of an irrigated area on southern chernozems to restore its fertility. Materials and methods. The object of research is southern chernozems located in the dry steppe zone of Semikarakorsky district Rostov region, irrigated with II class water. To study the ecological and reclamation state of the irrigated area, soil samples, in which the water extract and the soil absorbing complex (SAC) compositions, the total humus, and the granulometric composition were determined, were taken. The soil bulk density was determined in the pits by the ring method according to Kachinsky. Results. It has been stated that southern chernozems, despite the presence of alkalinity in the parent rock (2.04–2.24 mmol(eq)/100 g), in general, up to 160 cm are mostly non-alkaline. Significant changes were noted in SAC, in which there was an accumulation of exchangeable sodium (up to 5–7 %) and magnesium (19–24 % of ∑ SAC) and a decrease in exchangeable calcium by 8 % compared to the natural one. These negative phenomena provoked a decrease in the humus content to 2.83 % (with the optimal parameter for this zone being 4 %) and soil compaction to 1.37 t/m³. Conclusions. The actual data on the ecological and reclamation state of the irrigated area indicated the variability of the main properties of the southern chernozem during prolonged irrigation with water of an unfavorable composition towards their deterioration in comparison with the criteria for a favorable ecological state of these soils. To improve the ecological and reclamation state of the surveyed irrigated area, measures are proposed depending on the indicators, such as the accumulation of organic matter, deep loosening, chemical reclamation, soil saturation with calcium, and groundwater diversion.

Purpose: to assess the possibility of growing crops on soils contaminated with heavy met-als. Discussion. The danger of pollutants accumulation in the “soil – plants” system is deter-mined. The ways of inactivation of heavy metals in soil by improving its properties and increasing its buffering capacity are considered. Agricultural crop cultivation is possible on soils contaminated with heavy metals after assessing their content on the plots. Lands are allowed for development with background levels of contamination with heavy metals and a neutral reaction of the soil medium, but with the use of proven fertilizer systems. On soils with the heavy metals presence within the limits of maximum permissible concentrations (MPC), complex measures should be carried out in accordance with soil properties, including chemical reclamation, the organic and mineral fertilizers application and crops accumulating little pollutants (legumes, cereals and industrial crops) should be included in crop rotations. Soils that contain heavy metals above the MPC and on which it is impossible to obtain good-quality products should be used for cultivating crops which can be used as raw materials for industry (flax, cotton, etc.). Conclusions: the analysis of scientific sources showed that it is possible to grow crops on soil contaminated with heavy metals, but the above mentioned provisions should be followed.

Purpose: to study the soil properties in the rice system at Manych-Agro LLC, to determine their variability in the space of rice paddies and to assess the ecological state of soils. Materials and methods. On a representative plot, the groundwater table level (GWL), water-physical and physico-chemical properties of soils under different crops of rice crop rotation were studied. Soil samples in non-irrigated plots were also taken for comparative analysis (sunflower, winter wheat and alfalfa). Results. It was revealed that the soils in the arable layer of rice system of Manych-Agro LLC are characterized mainly by weak salinity, gypsum-bearing layers in depth. There is practically no alkalinity, but magnesium alkalinity prevails in the absence of sodium one and low content of exchangeable calcium in the soil absorbtion complex (SAC) in the 40-cm layer (from 60 to 72 % of the total SAC). The humus content is low to very low. The above mentioned negative properties of soils contribute to their strong compaction. Variability of soil properties indicators in space is different. The most significant soil variability was found in salinity (V = 103 %) and solonetzization of soils (V = 25...40 %), and insignificant – in exchangeable calcium (V = 10 %). Humus has an average variability (V = 16 %) for rice fields. Conclusions. The ecological state of soils is ambiguous. Exceeding the GWL, loss of humus and the increase in the proportion of magnesium in SAC characterize the situation as an ecological disaster, and an increase in soil compaction and a decrease in the amount of exchangeable calcium form an emergency situation. A relatively satisfactory situation is emerging in terms of soil salinity and exchangeable sodium.