The classification may be created on a basis of the analysis and grouping of the soil data or some typical images (standards) of the soil, which were imagined or selected from the existing data. These will be the representative profiles. The expression "representative profile or soil pit" may serve as a summary (denotation) of concepts different in meaning or content. As reference points may be taken mean, modal, or median profiles of the marked taxons, holotype – profile, which is the most similar to the whole taxon profiles. However, the calculated representatives are not entirely convenient because of the dependence on the volumes of multidimensional samples. Two approaches are combined. However, this also causes the increase of the subjectivity share, which is contained in the procedures of representative processes identification in the groups of initial objects. Nevertheless, we found more objective approach of typical samples detection, which is presented by the idea of classification-specification. The purpose of classification (genetic, factorial, substantive, combined, etc.) is determined through a fixed system of soil indicators (specificities) corresponding to this goal, organized in the form of a classification-specification graph. The number of objects for such a classification is determined by the number of gra-dation combinations for the values of the selected specificities (Кj), where j = 1,2, ... m, and m is the number of specificities taken into account. The edges of the graph reflect descriptions of representative images (types) of classification taxa. The word “type” here is related to the representative profile, and not to a soil.

The long-term dynamics of agrochemical properties for leached chernozem under an orchard monoculture has been studied. The objects of monitoring are two testing areas in the south (“Krasnodar”) and in the center of the European part of Russia (“Michurinsk”) without applying of organo-mineral fertilizers and chemical melioration to the soil. A significant decrease of the main fertility indicators within the soils humus horizon has been revealed during the period of intensive growth and stabilization of apple trees yields for the testing area in the south of Russia: a reduction in the nitrogen mineral forms stores and nitrification ability, and in exchange potassium stores. As for the area in the center of the European part of Russia, a trend for the content of mobile forms of phos-phorus and potassium decreasing during the growth and stabilization of apple yields has been revealed. The regression models obtained as a result of the anal-ysis were linear and revealed probable significant trend of the decrease for the observed indicators over time. Quantitative changes in the parameters of the organic matter content in soils within the boundaries of the testing area made it possible to identify the processes of dehumification: in conditions of monocul-ture at the natural level of fertility. During the period from 1990 to 2014, the depletion of soil organic matter contained 7.5%. It is shown that the processes of soil organic matter depletion occur differently under different soil and climatic conditions. It is established that apple plantations, consuming the amount of available forms of mineral elements needed for the forming of sustainable yields, create prerequisites for the development of processes of chernozems chemical degradation. Absence of fertilizers and chemical reclamation on this background contribute to aggravation of this process.

Available data on salt-affected soils of the Rostov lowland in the Upper Volga region and the Nero lake basin are predominantly based on observations made in the beginning of the last century. Modern studies of potential areas of soils salinization in this region are absent. As a result of the conducted investigations considering long-term stages of the groundwater level decreasing within the area of Rostov lowland on a background of the known trends of the climate change, the question on the salinization phenomenon is still opened. Following the results of the second cycle of monitoring investigations in 2016-2017, we made an assessment of the salinization degree of the subaqual landscape on the II terrace of Nero lake. The possibility of hydromorphic solonchaks forming was shown. The factors and conditions of their forming and the relatively sus-tainable functioning in the humid climate of the southern taiga subzone were examined. The seasonal dynamics of the profile distribution of water-soluble salts, carbonates, gypsum and storage of salts in two soil pits within the impact zone of the salty spring (the former salt industry center) was revealed. To identify the long-term salinization dynamics in the Varnitsy landscape the information on water types from the salty spring, groundwater and soil extraction over a period of a hundred years of sporadic observations was analyzed. The current monitoring data indicated active salinization processes in the landscape and salts migration beyond the soil profile into the associated system of the Nero lake tributaries.

Results of salinity assessment of irrigated soils at the Svetloyar Irrigated Mas-sive located in the Northern Sarpa Lowland (Volgograd region) are shown. Soil cover patterns suffered severe transformation under the impact of ameliorative activity during 45–50-year irrigation. There were 25–50% of Solonetz and sol-onetzic soils on the investigated territory before the construction of Svetloyarsk Irrigation System. In 2010-s there were practically no Solonetz soils, as the main part of solonetzic (nitric) horizons were cut and mixed with material of other upper horizons during the planning works. Soil cover patterns of irrigated massive presented by transformed solonetz complex with solonchakous (epiprotosalic in WRB-2015) and deep solonchakous (endoprotosalic) soils passed to a phase of salt leaching at the present. Horizons with soluble salts moved deeper from the layer 0–100 cm in 1990-s to the layer 100–200 cm in 2010-s. Soils have become very deep solonchakous (bathyprotosalic) with weak and moderate degree of salinity predominantly chloride-sulfate and sulfate composition of salts. Under current conditions, the application of the multispectral satellite information did not allow us to map the salinized soils on the investigated massive. Therefore, maps of salinity in the layers 0–100 and 100–200 cm were created by interpolation method (the method of Inverse Distance Weights) on the basis of experimental data obtained during field investigation in 2015 and 2016. The high content of toxic salts was revealed in soils at the western part and locally in the northern part of Svetloyar Irrigated Massive. These territories will be potentially the most hazardous for secondary salinization, if ground water level rises up (higher than 3 m).

To separate the aggregates into the inner part (core) and the periphery (bark), the aggregates were rubbed against one another. For this purpose, aggregates of 5–3 mm were shaken 48 hours on a over head shaker, they rubbed against each other, and gradually their bark was grinded, passing into the fraction <0.25 mm. To monitor the process, the abrasion efficiency from the change in the size distribution of the size fractions was periodically evaluated. At the end of the ex-periment, the carbon and nitrogen contents were determined in the fractions obtained. The distribution of the resulting size fractions was stabilized after 16 hours of the experiment, in the case of Chernozem under the steppe, and after 24 hours in the case of Retisol under forest. In the Retisol abrasion (from the large aggregates, the peripheral part separates and particles <0.25 mm are formed) were observed throughout the entire experiment. In Chernozem, after the first hour of treatment, fragmentation of the aggregates predominated, then in the next 10 hours abrasion prevailed, then again crushing dominated. Determination of the carbon and nitrogen content shows the anisotropy of aggregates in this parameter. Inside the aggregates, the carbon content is higher than at the periphery, with the C/N ratio indicating the predominance of poorly-decom-posed plant residues. Moreover, these differences are more expressed in uncultivated soils, and when comparing types, in Retisols in comparison with Chernozems. In general, the proposed approach is promising. However, it requires further development for an effective application.

The article describes the morphological and molecular genetic approaches used to identify the green microalgae of the Trebouxiophyceae class from the ACSSI collection. In the brown semi-desert and chestnut soils, we found Muriella ter-restris. In the buried meadow-chestnut soil we found Edaphochlorella mirabilis. Three more strains are characterized as new uncharacterized taxa: ACSSI 014 is a new species related to the genus Watanabea isolated from gray forest soil, with a pyrenoid surrounded by several starch grains, in contrast to the type species, and ACSSI 104 and 144 are a Nannochloris-like genus, whose representatives were found in solonetz and chestnut soil and are characterized by poor morphological specificities. It is shown that no single criterion (either morphological or other specificity, calculation of genetic distances, analysis and comparison of the ITS2 secondary structure, search for compensatory changes and molecular signatures) does not allow reliable classification of taxa. Therefore, due to this fact, it is necessary to apply a polyphasic approach in the systematics of algae, especially when identifying taxa with simple cellular morphology, which are often found in soils.

The results of large-scale (1 : 5000) soil mapping of allotments (garden non-commercial partnerships) located on the territory of Meshchera lowland of Noginsk district of Moscow region are considered. The investigations showed that the initial soils located on the territory of the allotments have suffered the significant transformation since the allotments were created. Predominantly soddy podzolic soils with the different degree of surface or ground gleization, and also boggy soils were transformed into the agro-soddy podzolic soils and agrozems. The most significant changes occurred within soils in areas of intensive development where the implementation of organo-mineral fertilizers, green manures, formed agrogenic (hummock) micro-topography, manmade microstructure of the soil cover. Compared to the natural soil profile, they are characterized by a neutral pH, high and medium content of mobile phosphorus, poor in exchange potassium. Soils with the medium humus content (3–5% humus) prevail in this area. We separated clusters characterized by the agro-chemical and morphological properties of soils reflecting the classification at the level of subtype. The revealed changes reflect the growth of productivity and quality of the allotment soils and determine the expediency of soil parameters consideration in the basic documents providing the register of soil resources at the local level.

Mineralogical composition of different texture fractions of Solonetz (Calcic Gypsic Endosalic Solonetz (Columnic Cutanic differentic) was studied. Inves-tigated object was located on the Borsi key plot in the northern part of the Caspian lowland (absolute height of the territory about 48 m) and developed on Early Khvalynian deposits. The profile of Solonetz is formed on coarsesilty clays and is characterized by depletion of silt in the upper 5cm horizon. The modern pedogenesis causes eluvial-illuvial distribution of silt fraction along the profile and the different ratio of mineral phases: 1) trioctahedral illites prevail in the SEL horizon, which indicates the process of illitization; 2) the upper natric horizon differs from the underlying ones by the predominance of labile minerals with the segregation of smectite packages. This pattern is associated with the process of lessivage, which occurs as the forming of clayey coatings. According to the mineralogical composition, some stratification of the soil-forming material is noted: in the upper part of the profile there was an increased content of illite of tridioctahedral type and mixed-layer minerals in comparison with the lower horizons. Comparing to the accumulative-calcareous horizons BCA and BSN3s the calcareous (Cca,s) horizon has a higher content of chlorite and kaolinite with perfect structure. The distribution of clastogenic minerals along the Solonetz profile in silt fractions and ≥ 10 μm has a weak disordered variation. With the increase of fractions sizes, an increase in the content of quartz, feldspars, plagioclases was marked. Also, the decrease of micas due to their more active disintegration during the pedogenesis was revealed.