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The long-term (30 year) dynamics of a solonetz soil complex composed of solonetzic light chestnut soils and chestnut solonetzes under standard conditions and with the application of agromeliorative measures are considered. When the standard zonal agricultural practice is used, the soils of the solonetzic complex have unfavorable agrophysical, chemical, and physicochemical properties and low productivity. After 30 years of the standard three-level tillage of the soils to a depth of 40–45 cm, the productivity of the biogeocenosis decreased. Thirty years after a single rotary-milling subsoil treatment of the 20- to 45-cm soil layer using a milling tool FS-1.3, there were no morphological features pointing to the restoration of the solonetzic process. The humus content in the 0-to 20-cm and 20-to 40-cm soil layers was 2.3 and 1.7%, respectively; the content of adsorbed Na+ in the 20-to 30-cm layer was 11.6% of the total exchange capacity, or 38% lower than its content in the reference soil. The additional yield reached 30–70% and more of that obtained with the standard agricultural technology used during the whole period under investigation. The method of systems biogeotechnology (systems bio-geo engineering) is proposed as a method for the preventive control of soil evolution and the maintenance of the stability and high productivity of the soil cover.

Dynamics of material composition, migration and accumulation of salts is determined by chemical equilibrium in soil solution. Soil solution contains associated electrically neutral ion pairs CaCO30; CaSO40, MgCO30, MgSO40, charged ion pairs CaHCO3+, MgHCO3+, NaCO3-, NaSO4-, CaOH+, MgOH+. Calculation method is proposed for quantitative assessment of real ion forms in the soil solution of chestnut solonetz soil complex. Were proposed equations to calculate free and associated forms of ions. To solve the equations were used an iteration, a linear interpolation of equilibrium constants, a Method of Ionic Pairs including a law of initial concentration preservation, a law of the operating masses of equilibrium system, the concentration constants of ion pair dissociation on the law of operating masses. Was determined the quantity of ion free form and a coefficient of ion association as ratio of ions free form to analytical content I³e = Cass/Can. The association of ions varies in individual soils and soil layer. Increasing soil solution salinity amplifies the ions association. In form of ionic pairs in soil solution are: 11.8-53.8% of Ca2+; 9.4-57.3% of Mg2+; 0.7-11.9% of Na+; 2.2-22.3% of HCO3-, 11.8-62.7% of SO42-. The ion CO32- is high associated, the share of ions in associated form is up to 92.7%. The degree of soil solution saturation was obtained for three level of approximation accounting on analytical concentration, calculated association coefficient, calculated coefficient of association. Relating to thermodynamic solubility product S0, the mathematical product of analytical ionic pairs indicated super saturation of soil solutions up to K1 = 100, taking into account calculated coefficient of association ion activity super saturation of soil solutions is absent, K3≈1. Only for solonetz chestnut meadow K3≈2-5. The soil solution saturation degree in soil profile and laterally in landscape varies. The quantitative assessment of real ion forms in the soil solution allows explain evolution of landscape of salted soils, structure of soil cover. Calculations fulfilled show that a possibility of soil degradation scenario taking into account the laws of association of ions in soil solution is much more probable and dangerous than it was assessed before. New understanding of water-salt transfer, geochemical barriers and ecological functions of soil will help to improve rainfed and irrigational agriculture.

The chemical equilibrium in the soil solution determines the dynamics of its material composition, migration and accumulation of salts. In the soil solution are formed electrically neutral ion pairs ÐiаÐiО3°; CaSO4°, MgCO3°, MgSO4°, charged ion pairs CaHCO3+, MgHCO3+, NaCO3-, NaSO4-, CaOH+, MgOH+. The calculation method proposed for quantitative assessment of real ion forms in the soil solution of solonetz taking into account the ions association. Determination of real condition of the main ions in soil solution is based on ion association and its influence on physical and chemical properties of solution. Were calculated the free and associated ion form concentration according to analytical ion concentration. Were used an iteration to solve the equations of ion material balance, a linear interpolation of equilibrium constants, a Method of Ionic Pairs including a law of initial concentration preservation, a law of the operating masses of equilibrium system, the concentration constants of ion pair dissociation following the law of operating masses. Upon completion of iterative procedure, was determined the quantity of ion free form and a coefficient of ion association I³e as the ratio of ions free form to its analytical content I³e = Cass/Can. For calculation procedure were used the own software products. The association of ions varies in individual soils and soil layers, Nˆncreasing the soil solution salinity amplifies the ions association. Depending on concentration and composition of soil solution the ionic pairs are: 15-45% Ca2+; 16-49% Mg2+; 0,6-8,4% Na+; 2,2-17,6% HCO3-, 16-51% SO42-, up to 88% CO32-. The proposed thermodynamic calculation method for quantitative assessment of real ion forms in the soil solution helps to explain the evolution of salted soils, maintain the soil, improve plant nutrition and irrigation.

Changes in the properties of solonetzic soil associations (chestnut solonetzic soils and chestnut solonetzes) in the dry steppe after their reclamation have been studied for 30 years. The reclamation included the deep three-tier plowing and the approach of rotary tillage. A single rotary tillage operation resulted in the formation of fine aggregates of equal sizes in the plow layer; any morphological features of the restoration of solonetzic pedogenesis are absent. The atmospheric moisture easily penetrates into the soil, and soluble salts are leached off to a great depth. In 30 years since the soil amelioration with the use of a PMS-70 rotary tiller, the humus content has increased up to 3.3% in the upper 20-cm-thick layer and up to 2.4% in the layer of 20–40 cm. The content of adsorbed Na+ in the 20- to 30-cm-thick layer has decreased to 10.6% of the cation exchange capacity (in comparison with 19.8% in the nonreclaimed soil). The spatial heterogeneity of the soil cover has decreased in comparison with that prior to the reclamation. During the entire observation period, crop yields gained from the fields reclaimed with the use of the rotary tiller have been by 25–60% higher in comparison with those on the fields with traditional treatments.

An effective technology of growing crops with tilling solonetz by a PMS-70 rototiller was developed. On the basis of a long-term field experiment, a 30-year period of influence of cyclic soil ameliorative farming practices of chestnut-solonetz complex soils of the Rostov oblast is substantiated.