The paper discuss the literature data on clay mineralogy of vertisols and presents the investigation of clayey soils formed in ultra-continental climate in the Eravna depression (Buryatia). Soils are formed on the watershed and shoulder positions of the local ridge and are underlined by permafrost. Morphological analysis of soils revealed a combination of cryogenic features (permafrost wedges and cracks, cryogenic structure, above permafrost gleyization) and vertic properties (slickensides, wedge-shaped aggregates). According to the morphology, the soils were classified as Dark compact soil or Gleyic Vertisol Glossic Gelistagnic on the shoulder position, and as Chernozem-like weakly compacted cryoturbated soil or Vertic Gleyic Phaeozem Glossic Pachic Clayic Gelistagnic on the watershed where vertic features were weakly expressed. According to physical properties and clay mineralogy, the shrinking-swelling potential of the soil on the watershed is comparable to the soil of the shoulder: almost the same, and in some horizons even higher content of clay (up to 76%), fine clay (up to 54%) and swelling components in the fine clay (<0.001 mm) fraction (93-98% of montmorillonite). However, in the ultra-continental climate of Buryatia and close-lying permafrost (depth to permafrost at the end of August was about 250-280 cm), the most contrasting hydrothermic regime and the most favorable conditions for the implementation of shrinking-swelling are created in the upper steep part of the south-facing slopes. Due to the fact that soils on the watershed receive more moisture and less heat, this results in less contrasting hydrothermic conditions and less pronounced shrinking-swelling processes. The lack of conditions for full realization of shrinking-swelling potential in clayey soils of watersheds is the reason for identification of vertic features at a lower taxonomic level.

The results of digital mapping of organic carbon content within the arable horizons of soils and the assessment of obtained models accuracy with the use of machine learning methods for the area of Central Russian Upland in Voronezh Oblast are presented. The digital mapping was based on 22 points of soil samplings, applied for the learning and verification of models, and also on several sets of predictor variables. We took also digital elevation model, its derivatives and also remote sensing data of different spatial resolution as predictor variables. Several methods were used to create the spatial variability models for the investigated property based on the decision trees methods: random forest, boosting regression trees and Bayessian regression trees. The assessment of the models obtained accuracy was conducted by a method of cross-validation. As the accuracy indices we used the determination coefficient, mean absolute error and the root mean square error. The modelling results showed that the use of predictor variables presented by digital elevation model, its derivatives and Landsat 8 data we were able to obtain more sustainable models. The determination coefficient varied from 0.6 to 0.7, RMSEcv, i.e., the prognosing error varied from 0.5791 to 0.6520. Whereas, the best model was obtained with the method of Bayessian regression trees; whereas the predictor variables presented by the digital elevation model, its derivatives and Sentinel 2 data determination coefficient varied from 0.47 to 0.55, and the prognosing error varied from 0.7031 to 0.7909. It was revealed that in the described models according to different data sets the most significant were the various predictor variables.

The mineralogical composition of clay (<1mm), fine (1-5 mm), medium (5-10 mm) silt and coarser fractions (>10 mm) of light fine solonchakous solonetz strongly salinized by sulphate-chloride highly calcareous with gypsum content light clay-light clay loamy-heavy clay loamy on the loess like clay loams (Chromic Calcic Gypsic Endosalic Solonetz (Albic, Episiltic, Epiclayic, Endoloamic, Columnic, Cutanic, Differentic)) located on the highest eastern part of Yergeni upland at about 70 km in the north from Elista (Kalmykia). The investigated profile is formed on the homogenous aeolian clay loam deposits. The elluvial and illuvial distribution of clay in the solonetz profile is accompanied by the changes in the ballance of clayey minerals in the above solonetzic and solonetzic horizon. The following processes occurwithin the SEL above solonetzic elluvial horizon: (1) the destruction of the mixed layer formations of mica-smectitic type with the residual preservation of mixed-layer chlorite-vermicullites in clay; (2) the relative accumulation of trioctahedrical micas within the clay; (3) the outflow of the clayey (<1mm) particles down the profile. Within the solonetzic BSN horizon the mixed layer mica-smectitic formations are formed with the high content of smectitic packages. Such an accumulation is a relative within the clay composition ,and it is absolute within the solonetzic horizon, comparing to the soil forming rock. The differentiation coefficient according to the mixed-layer formings is lower within the clay composition, however, it is higher within the composition of the soil in general, comparing to the clay illuviation degree. The silty fractions consist of quartz, plagioclases, potassium feldspars, and micas with the mixture of chlorite and caolinite. The increase of fraction’s amount is accompanied by the increase of the quartz content (from 20-27% in the fine silt fraction to 50-58% within the fraction of >10 mm), plagioclases (from 10-13% to 21-28%), potassium feldspars (from 9-13% to 15-20%), and the decrease of micas content (from 30-40% to 4-9%). The minerals distribution within the silt fraction along the solonetzes profile is relatively homogenous.

The rill erosion affects significantly on the processes of arable soils degradation. Therefore the aim of the work was to continue the development of hydraulic and statistical methods for assessing the transportation of soil material by shallow streams. For this purposes, we conducted the verification of shallow water flows transporting capacity equation. As an object we used typical chernozems with medium depth light clay loamy on loess like clay loams deeply tilled non-eroded, weakly eroded and medium eroded. Samples for the purposes of the study were collected in the Kursk region. The comparison of the experimental and calculated by the equation turbidity values showed a satisfactory correspondence. The average relative error of calculations contained in modulo 18.0%, and the correlation coefficient was 0.89. The model experiment on a large erosion flume, revealed that the weighted average diameter of the aggregates moved by the flow is increased as the flow velocity is also increased. However, the diameter of aggregates deposited in the bed is decreased. This regularity was revealed as with air-dry initial state of the samples and with capillary-moistened initial state. It was found that the water flow with the low speed (0.3915 m/s) first of all washes out the multi-ordered and the densiest humified aggregates (including coprolites), whereas the pieces of less humified aggregates and separate mineral grains are accumulated on the bed. We revealed that this is quite specific for both types of the initial states of the samples. It was noted that the fractions sizes of the aggregates washed out by the flow at both initial states of the samples are congruent; the same is true for aggregates deposited in the channel

The content of microelements is determined within the alluvial soils of the flood plain situated near the river bed in the middle flow of Amur River. The impact of the catastrophic flood of 2013 on their content is also revealed. The microelements were determined by using mass spectrometry in samples collected from genetic horizons. The principal component analysis has been applied to characterize the relationship between microelements, alluvial soil properties and macroelements composition. The associations of accumulation (Rb, Sr, Ba) and association of dispersion (Zr, Ta), having a lithogenic nature, are separated. The content of other microelements is lower than the average one for the world's soils. However, their concentration increases as the distance from the river bed increased. It is revealed that trace elements under the impact of flood waters are not accumulated only. They are also leached. Their migration is influenced significantly by floodplain topography: microelements are more affected to washing out in soils which are located near the river bed. Other factor which affects the microelements migration is the soil properties. Some microelements (Sr, Cd, Ba, Pb) are washed out from all types of soils. While the other ones (Y, Sc and Cr) are accumulated only. Flood affected greatly Mo (+43% average for the soil), Sc (+38%), Cu (+27%), Cd (-23%), Pb (-12%) and Sr (-12%). However, before the flood, significant correlation between microelements were observed only for exchangeable manganese and oxides aluminum and magnesium. Significant correlation between texture, organic matter and soil pH appeared after a long flood in all studied soils. These changes are probably caused by a decrease in the redox potential during flooding and the washing out of calcium oxide.

The experience of the agriculture biologization is assessed on the example of the “Slava kartofelju” Agrofirm situated in the Komsomolsky District of the Chuvash Republic. The soil is presented by medium loamy leached chernozems. The content of humus in the arable layer varies from 7 to 11%, and the depth of the fertile layer varies from 50 to 110 cm. Soil-forming rocks are loess, loess-like loam (varying from light loam to heavy loam). In each crop rotation, perennial fabaceous or fabaceous-cereal crops were necessarily present. Straw and fertilizer were implemented to the soil in order to improve the balance of humus and biological parameters. Within the area of pea and cereals cultivation, due to the straw incorporation into the soil 36.6 kg of nitrogen, 16 kg of phosphorus and about 66 kg of potassium were returned to the soil per hectare on average. The share of melilot in the structure of crop areage contained 21.3%. In 2016 the amount of nitrogen, phosphorus and potassium which entered the soil with melilot green manure mass contained: for nitrogen - 1055 t of ammonia nitrate, for phosphorus - 194 t of ordinary superphospate, for potassium - 470 t of potassium chloride. For the repeated green manuring after the melilot incorporation into the soil in 2016, the oil radish was sown in the beginning of the third decade of June on the area of 429.6 ha. The positive balance in potassium and phosphorus content was achieved due to the use of straw and broad implementation of green manure. Therefore, the share of biological nitrogen in the balance contained 76.3%, mineral nitrogen 23.7% correspondingly, and as for phosphorus and potassium it contained 42.6 and 68.0%