Table of contents

Soil Physics is an interdisciplinary branch of science with roots in Physics and fruits in Soil Science, Plant Science, Atmospheric Science, Ecology, and Microbiology. Key concepts of Soil Physics provide a basic framework for cooperation and research on vital environmental problems, such as soil erosion and degradation, water scarcity, groundwater pollution, global climate change, loss of biodiversity. Related topics were discussed at the International Conference «Key concepts of soil physics: development, future prospects and current applications» held in Moscow on May 27–31, 2019. The conference papers included in this volume concern the following issues: the intra-soil surface phenomena and microlevel interactions, soil pore space, soil structure and architecture; soil hydrology and transport phenomena in soil and landscape; soil temperature and climate change; issues of agriculture, food security, land reclamation, urban soils; mathematical modeling in soil physics and environmental science.

All papers published in this volume of IOP Conference Series: Earth and Environmental Science have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

The International Conference to commemorate the 90th anniversary of A. D. Voronin's birth «Key concepts of soil physics: development, future prospects and current applications» was held in Moscow on May 27–31, 2019. The topics of the conference were: soil solid phase (surface phenomena, soil structure and pore space); fundamental and applied aspects of soil hydrology; migration of toxicants and salts in soil; matter and energy fluxes in soil and landscape; soil temperature and cryogenesis; spatio-temporal heterogeneity and soil evolution; mathematical modeling in soil physics and environmental science; the intra-soil physical conditions and their impact on soil biota; recultivated and urban soils; scientific and applied aspects of land reclamation; food security and digital (smart) agriculture as modern challenges of applied soil physics.

Presented are the results of comparative studies of sod-podzolic soil, typical chernozem and chernozem merged in different land use conditions. While identifying the physicomechanical properties under loading-unloading cycle, it was revealed that the soils with the highest percentage of physical clay demonstrate a higher capability of restoring the soil structure.

From the samples of gradually drying (beginning from the field moisture capacity, FMC) soddy-podzolic sandy loam soil (Albic Retisol (Loamic, Ochric)) contaminated with Zn were isolated the soil solutions (SS) by centrifugation, while from the other samples of the soil, moistened to FMC, various energy fractions of the SS were pressed using a hydraulic press. The acidity of the centrifuge solutions extracted from the soil of the experiment variant with the cultivation of plants ("barley") was, on average, 1 pH higher than on "bare fallow", and decreased with decreasing soil moisture content. The acidity of the solutions extracted from the soils of the "bare fallow" variant in the same range of soil moisture content practically did not change. It was also found that in more acidic solutions from the "bare fallow" variant the content of Ca, Mg, Mn, Zn and K was 2.4 – 6.9 times higher than the content of these metals in solutions from the "barley" variant. The positive correlation between pF and pH was clearly observed for the pressed solutions from the soils of both variants. Concentrations of Ca, Mg, Sr, Ba,Zn, K and Na in successively pressed fractions of SSs from more acidic soil of the "bare fallow" variant, on average, 3.0 – 8.4 times exceeded their concentrations in similar fractions of solutions of the "barley" variant and showed an inverse correlation with soil moisture (pF value).

In 2012 - 2018 water regime monitoring was carried out at two areas of Cambisols (non-gleyic and Gleyic) in autonomous relief positions (hill tops) of the Sambian hilly moraine plain (Kaliningrad region). Differences between soils in duration of the desiccation period (moisture content < lento-capillary point) and overmoistening period (moisture content > field capacity) in the 0 - 20 cm and 0 - 100 cm layers are established. Formation of zones with critical air supply (aeration porosity below 10%) has been studied.

Thermal diffusivity of peat, quartz sand, and their mixtures was studied at different water contents using the unsteady-state method. Quartz content in studied samples was 0.00 m³m⁻³ (pure peat), 0.05, 0.10, 0.15, 0.20, 0.30, 0.40, 0.50, 0.55, and 0.62 m³m⁻³ (pure sand). Thermal diffusivity of air-dry samples varied from 0.6×10⁻⁷ m²s⁻¹ for pure peat to 7.0×10⁻⁷ m²s⁻¹ for pure sand. Thermal diffusivity of moist samples grew by two-four times as compared to dry samples. Small amounts of quartz material with separate sand particles distributed within the peat didn't contribute much to the heat transfer through the studied media, and the thermal diffusivity of mixtures with quartz contents of 0.05 and 0.10 m³m⁻³ was practically the same as that for pure peat. Vice versa, there were pronounced differences in thermal diffusivities between the samples with quartz contents of 0.55 and 0.62 m³m⁻³. It means that addition of small amounts of peat to the sand material results in significant lessening of thermal diffusivity. We assume that there is a kind of threshold between the quartz contents of 0.10 and 0.15 m³m⁻³, after which the continuous sandy chains are formed within the peat, which can serve as preferential paths of heat transport.

The study is the first attempt in soil physics to estimate the effective specific surface area of strongly swelling polymer hydrogels as soil conditioners of a new generation. Along with the standard assessment of water vapor desorption isotherms by the BET method, a new method for determining the specific surface area deduced from the slope of water retention curves was used. Water desorption isotherms and water retention curves were obtained by a dynamic sorption equilibrium method and by a new method of thermodesorption. The specific surface area values of synthetic polymer hydrogels ranged from 468 to 1029 m²/g. An innovative Russian product VM-P with amphiphilic filler in the form of dispersed peat had the maximum specific surface area among all studied types of hydrogels. Water absorption properties and dispersion of gels have a hysteresis caused, presumably, by the dynamics of dispersion in the cycles of wetting-drying.

The dependence of Cu²⁺ and Zn²⁺ adsorption by Chernozems of the Rostov region on the soil texture was examined. The thermodynamic parameters of the Langmuir equation (K_l and C_∞) were calculated for all the studied samples. According to the adsorption parameters, the metal cations were arranged in the order Cu²⁺ > Zn²⁺. The adsorption of the studied heavy metals and the strength of their fixation on the surface of soil particles decreased with a decrease in the percent of the clay fraction in the particle size distribution of the soils. A correlation analysis of the relationships between the adsorption parameters and the contents of particles <0.01 and <0.001 mm in the soil samples showed that the maximum adsorption (C_∞) of the metals mainly depends on the particle size, whereas the strength of adsorption is largely controlled by the chemical and mineralogical composition of the soil particles.

The results of soil hydrophysical parameters modeling by neural networks are considered. Modern computing facilities using pedotransfer functions provide simplicity, speed and cheapening of obtaining soil characteristics by mathematical calculations. The initial data are the basic properties of the soil, which are stably determined. The analysis of errors in the calculation of hydrophysical parameter was conducted. Obtained neural networks most accurately reproduce hydrophysical parameters.

The surface horizons of the soils of traffic areas of Rostov-on-Don are characterized almost twice higher content of soil particles from 1 mm to 0,01 mm than native chernozems. The higher anthropogenic load provides the higher the content of sand fractions in the particle-size distribution. The accumulation of heavy metals (HM) in urban soils of roadside areas is relatively small, which is also due to a decrease of the soil sorption capacity. Significant excess of the estimated permissible concentrations was detected only for zinc and lead, and the higher the pollution level, the weaker the correlation between the particle size distribution and the HM content. This is justified by the influence of external factors on the accumulation rate of chemical elements.

Soil surface wettability is the main physical property that defines organization of elementary soil particles into soil structure. Human impact affects the changing in properties of soils under arable land use. The objective of this research is to study this impact by the example of two profiles of Chernozems (Kursk region), located under the forest and at the arable field. For both profiles some soil solid phase properties (contact angle, aggregate composition, aggregate waterstability) were measured. There was a positive correlation between the content of organic matter and soil's wettability in studied soils – a growth of contact angle with the increasing the content of organic matter. Under the forest the content of soil organic matter was changed from 6.41% on the surface to 1.9% at the depth of 100 cm. In the Chernozem under the arable land use the organic carbon content in arable horizon is almost two times less. The maximum of hydrophobicity (78.1°) was observed at the depth of 5 cm under the forest. In the profile at the arable field the contact angle value at the same depth was 50°. The results of the structure analysis showed a decrease in the content of agronomically valuable and water stable aggregates in the profile under arable land.

Several well-known mathematical models of concentration fields in the soil (both at the single aggregate and the profile scales) are considered. It is shown that the respective boundary value problems for steady-state profiles belong to the class of ill-posed problems, since their solution does not exist. It occurs because a certain set of processes (for example, diffusion transport + first-order kinetic of the consumption) restricts possible boundary conditions, which, therefore, can no longer be arbitrary. Ill-posed inverse problems are also briefly described as well as one ill-conditioned inverse problem of parameters identification for mathematical model of the soil organic matter concentration profile. Exact solution for this model is the sum of two exponents. For a certain input data it was shown that this problem belongs to the class of ill-conditioned, since a small bias in the input data causes a significantly larger error in the solution (i.e. in calculated parameters).

The yeast communities of tropical soils of two biotopes in monsoon tropical forest in the specially protected natural territories of the National Park Cát Tiên were studied. It was possible to establish that the distribution of yeasts in the profile of studied soils differed markedly. Of particular interest was the isolation from the tropical soils of Vietnam the pedobiont yeast species Saitozyma podzolica, which is regularly found in soils of temperate latitudes of Russia and other regions.

In the process of nesting activity ants change the physical characteristics of the soil. We studied penetration resistance of ants' nests, their temperature regime and particle size distribution for the nests of three soil-dwelling ants species (Lasius niger, L. flavus and Formica cunicularia). Control sites were located in different regions of Russia (Ryazan region and Arkhangelsk region) on different soils (post-agro-sod-podzol gley sandy loam on alluvial-deluvial sediments in Ryazan region and developed sod-podzolic, light loamy soil on the moraine in Arkhangelsk region). So we found out that ants can reduce the penetration resistance of the soil by 8 times compared to the control (66 kPa in control soil and 7,8 kPa in ants nests). The temperature regime of anthills is more aligned and the average temperature of ants nest was lower than in the control (21,4 °C in the control soil mound and from 20,8 °C to 17,7 °C in ants nests depending on their species). The particle size distribution, by contrast, was more variable compared to the control.

The soil cover of the Vladimir Opole was investigated by the method of long (up to 40–50 meters long and 1.5 m deep) transects. Four Qualifiers of Phaeozem (PH) were morphologically identified: albic, gleyic densic, grayzemic and PH cambic with the 2nd humus horizon. Agrophysical studies of soils in transects included layer-by-layer determination (every 20–40 cm along the trench, and at depths 0, 20, 40, 60 and 100 cm) of soil density, water permeability, and penetration resistance. The soil compaction (up to 1.57 g cm⁻³) was observed, which was especially pronounced in a layer of 20–25 cm and connected with the agrotechnological impact. Simultaneously, friable (<1 g cm⁻³) and, therefore, zones with high moisture capacity confined to PH with 2nd humus horizon, showing that the change in agrophysical properties in the soil cover occurs gradually, continuously and regularly and is determined by both pedogenetic and agrotechnological factors.

Physical properties and their dynamics under anthropogenic impact are important for the rational use of urban soil and its fertility management. However, due to the urban soils anthropogenic transformation features some classical methods are not applicable in specific cases. Thus, the cutting ring method for determination a soil bulk density does not give objective results in horizons with a high proportion of anthropogenic inclusions. The microtomographic method allowed us to obtain new information on the parameters of the pore space of the humus-accumulative horizons of urban soils. It is shown that the value of closed porosity is the most informative diagnostic indicator of the soil structural condition. Simultaneously, anthropogenic transformation of the soil is accompanied by a significant change in the volume of closed pores. The diameter of macropores visible in tomographic sections increases in the sequence: Urbic Technosols, Technic Chernozems (Calcic), Haplic Chernozems (Calcic).

The influence of prehistory and chemical properties of soils on their allelotoxicity was studied. 12 soil samples of East-European Plain, 6 seeds' cultivars of spring wheat and seeds of barley, rye and triticale were used in the research. It was found that all studied cereals are inhibited by soil allelotoxins according to the revealed regularity. Soil samples from territories of agricultural use are characterized by a greater allelotoxicity compared with fallow and forest areas. Experimental data suggest that crop rotation applying not always able to reduce soil fatigue. For this reason, it is necessary to assess the real soil fatigue (soil allelotoxicity) when using the crop rotation.

The soil cover of the territory of Baikal region is characterized by a significant variety, and the structure of soil cover – by a high complexity due to complex geological history of the region, to the influence of tectonic processes of the Baikal rift zone, to the wide spread of young mountain systems, island permafrost and other factors. Distribution of loess rocks at the territory of the forest-steppe zone of Baikal region contributes to the genesis of fertile soils, but increases the heterogeneity of soil cover, which should be considered in agricultural land use.

Regularities of spatial variability of the structural state of soils in rainfed and irrigated regions of Azerbaijan are discussed with application of classical statistics and geostatistics. The highest coefficient of variation is observed for water-stable aggregates >3 mm (106 %), and the lowest – for 10-0.25 mm (7.9 %). The results of geostatistical analysis show a strong spatial dependence of the indicators of wet sieving at irrigation. Structural indicators are mainly approximated by spherical and exponential models in irrigated soils, but in rainfed conditions, by linear models.

The interdependence between the rheological properties and the water retention curve was determined on the example of typical chernozems of Kursk region. The strength of the aggregates of humus horizons of a virgin chernozem, an arable chernozem, and aggregates of Bca horizon in a wide range of water content was investigated by the conical Rebinder's plastometer. It was shown that the strength of the aggregates depends on water content. The dependence of aggregates strength on moisture is exponential. Comparison of virgin and arable soils revealed a positive effect of organic matter on the structural state of the soil. At high water content, aggregates of the virgin soil are more stable than aggregates of the arable soil and ones of the lower horizons Bca. In air-dry conditions, the strength of aggregates from the arable soil significantly exceeds the aggregates' strength from the virgin soil, which indicates degradation processes in the arable soil, a decrease of organic matter content leads to an increase of interparticle interaction and an increase in a block-like structure. These experimentally obtained data confirmed the existence of a close relationship between logarithm's values of the soil moisture full potentials' moduli and the strength of soil aggregates and the presence of an appropriate linear regression dependence. Voronin's structural-functional concept is confirmed by the fact that hydrophysical, mechanical and rheological properties of soils are functions of the soil structure.

The paper considers some examples of secondary carbonates in edaphic ecosystem components (soils, river and lake bottom sediments, suspensions). In addition to calcite, more soluble and less stable polymorphic modifications of calcite vaterite and aragonite, which are important precursors of carbonate-forming systems, are diagnosed. Microforms of vaterite are formed in presence of low molecular weight amino acids. In turn, microforms of aragonite are associated with extremely high salinity of water. According to the nonclassical mesocrystal concept, stability of vaterite and aragonite in situ is explained by the formation of mesocrystals – hierarchically organized superstructures from nanocrystals. The mesocrystal concept may be an important key to understanding the micro-and macroaggregates in soils.

Statistical cumulative distributions of indices for shrinkage curve of 324 monoliths from Vertisols and Vertic Solonetzes are created. Natric and vertic horizons have similar range of shrinkage indices, with that natric ones have higher values of pore volume weakly changed during water evaporation and lower bulk density at shrinkage limit.

The rheological parameters of naturally structured and homogenized sod-podzolic soils and typical chernozems under various land use were studied by the amplitude sweep test. The range of elastic behavior at low loads in which the microstructure does not break down (LVE-range) and the strength (stability) of natural structural bonds (storage modulus in this range) in naturally structured samples are greater than in homogenized samples but homogenized soils have a bigger range of plastic behavior (Crossover) at measurement conditions. Differences in rheological behavior between horizons are more pronounced for naturally structured soils. However, further studies and selection of optimal measurement conditions are necessary for better understanding of rheological behavior of naturally structured soils.

Mobility of cyanthraniliprole, paclobutrazol and metribuzin was investigated on large lysimeters of the Experimental Soil Station of Moscow State University . Pesticides were applied in recommended and tenfold rates for cyantraniliprole and paclobuyrazol and recommended and eightfold rates for metribuzin. All three pesticides were detected in leachate. Cyantraniliprole was detected in most water samples analyzed. The maximum concentrations of cyanthraniliprole in the leachate were 2.6 and 12.5 µg L⁻¹ in lysimeters with recommended and tenfold rates, respectively. Paclobutrazol was found 3 and 7 times during the year after application in the lysimeter with recommended and increased rates in concentrations up to 26 μg L⁻¹. Used in accordance with the regulation, metribuzin in leachate was detected once, in eightfold rate - 73% of water samples; maximum concentration was 180 µg L⁻¹. The migration risk into groundwater of all three studied pesticides is assessed as high, risk for people as low, risk for aquatic organisms as high. Risk and danger assessment based on simulation with model PEARL and mobility indexes showed high agreement with the assessment according to the experiment.

Main features of water regime of Umbric Albeluvisols Abruptic and Gleyic Albeluvisols Abruptic were studied. Two layers of surface water appear in soils in spring and fall, hence, the yields are decreased or crops die. Drainage is shown to eliminate surface water. Plastic drainage causes more intensive drainage effect than ceramic trench drainage in wet years. Regardless of the type of drainage, it is always an additional reason for the deep desiccation of surface soil horizons during the summer drought. Drainage leads to an increase in specific surface area of soils, total soil porosity, number of water stable aggregates, including those in the lower horizons. Favorable conditions for the cultivation of crops, especially for grain crops, are formed on drained soils of the Nonchernozem region.

The solid phase of Greyzemic Phaozems Albic was studied in the paper as an archive of palaeoenvironmental information. Textural differentiation of soil profiles was observed by the granulometric fractions content. The features of second humus horizon formation were described based on water regime, granulometric composition, mineralogy, porosity, specific surface area studying. Such characteristics as texture similarity index and loessation coefficient are also involved for this purpose.

Specific microrelief marked by white chalky spots at the soil surface was studied in Volga-Ural region. The microrelief was described and soil features were studied in a soil trench across the microrelief including morphology and further micromorphology in the thin sections with the aim to better understand the genesis and functioning of chalky polygons, and to testify the hypothesis of their cryogenic origin. Wide range of cryogenic features was found both at macro- and microscale. Some are expected to be relict, while the other features are supported or formed by modern cryogenic processes. The further investigation of the temperature regime is planned to investigate the spatial diversity and role of winter freezing in the modern squeezing of wet powdery chalky material to the soil surface.

Beneficiation products of phlogopite mining waste have been studied in terms of their use in soil engineering to improve soil hydro-physical and physicochemical properties. Vermiculite and lizardite minerals, parts of the obtained products, can interact with acid solutions and can be used to reduce the acidity of agricultural soils as well as to rehabilitate acidified industrial landscapes. The plant testing results indicate a positive effect of vermiculite-lizardite materials on plant growth and development.

An assessment of the state of soil invertebrate complex, litter horizons, and soddy-podzolic soils (Albic Retisols) in Moscow forest parks ("Bitsevskii Forest" and "Losinyi Ostrov") as a function of the level of recreational loads is presented. A clear pattern has been established for the deterioration of the soil invertebrates as the recreational load increases. This occurs as a result of changes in their habitat conditions, largely due to changes in the soil water regime and soil invertebrate feeding conditions. The abundance, biomass and diversity of soil invertebrates decrease by a factor of 2–2.5 under the influence of the recreational load. The condition of soil invertebrates is a sensitive indicator, which depends on the conditions of their habitat and is mainly determined by changes in the characteristics of the litter and soil properties.

This study presents the thermal diffusivity vs. moisture content curves for sandy soils of the East European Plain. Nine undisturbed soil cores 70 mm in height and 50 mm in diameter were studied in laboratory using the unsteady-state method. Thermal diffusivity of air-dry samples varied from 2.30×10⁻⁷ to 4.16×10⁻⁷ m² s⁻¹. The experimental moisture content – thermal diffusivity dependencies demonstrated pronounced peaks at 0.03−0.10 m³ m⁻³ moisture contents. Peak values of thermal diffusivity were from 8.25×10⁻⁷ to 9.86×10⁻⁷ m² s⁻¹. Statistical analysis was performed for 23 sandy samples including the newly studied ones and those earlier investigated with the same unsteady-state method. The ranges of sand, silt, and clay within the whole dataset were 73−97, 0−25, and 1−6%; wet bulk density varied from 1270 to 1820 kg m⁻³, organic carbon ranged from 0.1 to 1.7%. Each experimental curve was parameterized with a 4-parameter function. The parameters of average moisture content – thermal diffusivity dependencies were also obtained for (1) all sandy soils, (2) sandy soils with organic carbon content of 0.5% and greater, (3) sandy soils with organic carbon content less than 0.5%.

In Albic Retisols, Stagnic Fluvisols and Gleyic Fluvisols processes of ferriferous and manganese transformation follows rather active, that create new ecological niches for soil microorganisms.The study of concretions in the Albic Retisols, Stagnic Fluvisols and Gleyic Fluvisols showed, that the most characteristic feature of the prokaryotic community was the higher number and diversity of recoverable bacteria in comparison with the same indexes in the host horizons. The representatives of phylum Proteobacteria (class Gammaproteobacteria and Deltaproteobacteria) were dominant in the microbial communities in studied concretions. For the first time, the bacteriophages were found in concretions among them tailed phages were dominant. The method of the high-throughput sequencing of the 16S rRNA gene allowed to reveal the variability of the prokaryotic community in concretions of the Albic Retisol (Cutanic, Siltic), which was characterized predominantly by 7 bacterial phyla and 2 archaea phyla Both groups of organisms typical of soils and prokaryotes capable of transformation of iron and manganese under aerobic and anaerobic conditions were revealed in soil concretions. The specific characteristic of the studied soil concretions was a widespread occurrence of filtered bacterial forms, which may be considered as specific survival forms in soil loci.

Application of molecular biological techniques in environmental studies provides a more complete information concerning the taxonomic diversity and potential hydrolytic activity of soil microbial complexes that exist in a wide range of environmental factors. Among the key environmental parameters that determine the functional activity of the hydrolytic complex of soil layer, the most significant one is moisture. Moisture levels providing maximum activity of a hydrolytic microbial complex depend on the soil type. At high levels of moisture and temperature, the role of prokaryotic organisms, mainly actinomycetes, in the microbial complex significantly increases. It was discovered a new functional activity of actinomycetes in the hydrolytic prokaryotic complex: their controlling influence on the respiratory level of the complex in a wide range of parameters (moisture, organic matter, successional time).At the optimum for the life of most microorganisms levels of moisture (60% of field capacity) and temperature (27°C), representatives of Firmicutes and Actinobacteria phylums stand out among chitinolytic and pectinolytic dominants of the studied soils within the Bacteria domain. With increasing moisture and decreasing temperature the proportion of Proteobacteria increases. With decreasing moisture and increasing temperature, there is an increase in the amount of unicellular actinobacteria.

The topsoil bulk density of two abandoned small rural settlements situated at Tver and Yaroslavl regions of Russia was studied. The key sites had light grain soil texture. They had a long history of rural land use, and they were abandoned simultaneously. There were no stone buildings. The values of the abandoned rural settlements' topsoil bulk density are correlated with the land use type and the time of reforestation. The topsoil bulk density of the former buildings and the dirt roads was significantly higher than the one of the plough horizons of the former gardens, orchards and arable lands (1.7 and 1.4 g/cm³, respectively). Soil horizons of former buildings' territory are characterized by coarser granulometric composition of fine-grained fraction; however, they do not differ from plough horizons in bulk density that may be related to 2-3 times higher organic carbon content.

Prediction of soil temperature at an acceptable level of accuracy is essential for managing soil temperature at large scales since its measurement is costly and not practical due to its high spatial and temporal variability. This study was carried out for:: 1) Calculate the coefficient of thermal conductivity using classical methods and basing on data from measured soil profile temperatures in column and field conditions and 2) compare the results of the calculated and measured soil temperature, calculated from these data for both conditions. Soil temperature was measured with thermal sensors on both soil profiles in the field and soil column. The measured temperature values were similar in soil column and profile across 0.05, 0.10, and 0.20 m depths, but had the difference for 0.30 cm. The introduction of the second harmonic allows determining with high accuracy the parameters (T0, Ti, εi) of the temperature distribution on the field and column soils surfaces. For example, respectively for the harmonics n = 1 calculated the following statistical characteristics: R² = 86.45%, σ = 3.26, A = 13.07%, UII=0.12 and for n = 2: R² = 98.64%, σ = 1.09, A = 4.20%, UII=0.04. It was found that, mean values for soil thermal diffusivity (k), thermal conductivity (λ), damping depth (d) and heat absorptivity (e), calculated by amplitude, arctangent and logarithm methods, for the column were greater than those for soil profile, in all the cases.

The concept of probabilistic determinism is proposed to overcome a problem of significant soil variability which complicates finding of adequate models of soil development. Probabilistic and information indicators as characteristics of evolution of complex systems expand borders of use of soil texture results, allowing correct comparison with other natural and artificial systems on the earth and other planets. Probability distributions, statistical entropy and information divergence of granulometric fractions' contents are investigated. It is suggested to use these functions as statistical standards of granulometric composition for territory. Regularities of change of probability distribution functions and scale-independent information characteristics allowed receiving holistic numerical assessment of influence of processes of sedimentation, weathering and soil development also geological and contemporary deflation and anthropogenic impacts on probability structure of granulometric fractions contents.

The value of the fractal dimension of the soil structure is usually calculated by the geometric method based on particle size distributions. There is a hope to express soil-hydrophysical functions through the fractal dimension of the soil pore space found in some more direct, simple and physically independent way.

A three-dimensional hydrodynamic model was applied to derive the spatial patterns of the air flows and CO₂ fluxes within and around a recently clear-cut area. Results of modeling experiments show a strong influence of the clear-cut on the spatial air flow and vertical and horizontal CO₂ flux patterns. The CO₂ fluxes at the soil surface, within and above a forest canopy varied significantly depending on weather conditions, prevailed wind direction and influenced by the geometry and size of the forest clearing, tree density and the distance from the forest edges. The rates of horizontal CO₂ exchange near the ground surface especially within the downwind forest area and at the leeward forest edge were relatively large and comparable with vertical CO₂ fluxes.

Biochar is a carbonized, stable product obtained by pyrolysis. Due to its structure, chemical composition and characteristics biochar can change soil properties over a long period. To study the effect of woody biochar on loamy sand Spodosol, a small-scale field experiment was conducted. Following treatments were used in the experiment: soil-control, soil with biochar at a rate of 5 t ha⁻¹, soil with nitrogen fertilizer at a rate of 90 kgN ha⁻¹ and soil with combined application of biochar and N fertilizer. Application of biochar increased water-holding capacity of the soil in the range of plant-available water by 7%, in average, increased soil moisture 1.13-1.19 times, reduced the soil bulk density by 5% and led to a short-term increase in soil pH.

The necessity of creating multi-scale soil-landscape maps for making scientifically based decisions on soil melioration at all levels is substantiated. Multi-scale soil-landscape maps are called a system of interrelated maps of all scale ranges, obtaining automatically from expert integral polygonal layers, having a single classification basis, containing integrated information about soils and landscapes and displaying soils not only as independent natural bodies (that is, systems) but also as derived elements of landscape systems. The ways of integrating heterogeneous information about soils and landscapes contained in cartographic and textual sources are named. The concept of "global data integration" is revealed and the importance of its implementation in relation to the soil and landscapes is emphasized. The advantages of multi-scale soil-landscape maps are shown in comparison with traditional and modern digital soil maps, which are due to the use of the genetic hierarchical Soil-Landscape Classification System as the classification basis.

When creating "Zaryadye Park" in the center of Moscow, the tasks of creating soil constructions and artificial plantations were solved. The task was to form landscape-analogs of all natural zones of the European territory of Russia from tundra to subtropics in one small park in the center of Moscow. Based on the climatic conditions of the city, the selected range of plants, recreational load and the regime of visiting the park, a certain structure of soil cover was suggested, which is formed on the roof of underground constructions. The creation of fertile substrate and vegetation cover lasted from October 2016 till June 2017. 2 months after the planting had been completed, the first determination of soil properties in various types of forest stands was carried out.

Soil temperature is a sensitive climate indicator. In this paper, we used data from weather stations located in various natural zones of the European part of Russia to demonstrate how the soil temperature responded to modern climate change. The most intensive warming is observed at the beginning of the 21st century. The average annual air temperature for the period 2001–2015 increased compared to the period 1961–1990 by 1.2–1.4°C. The average annual soil temperature has increased in all studied soils and at all depths by 0.5–1.0°C. Soil warming is observed in both warm and cold periods of the year. However, soil temperatures have changed differently in different seasons of the year. The increase in air and soil temperature leads to a shift of the soil-climatic zones to the north.

The work is based on the idea that the shape and orientation of soil pores are among the direct indicators of the structural state of the soil. The specific features of the quantitative assessment of the shape of pores in two-dimensional sections by the degree of its difference from the circle are considered. To improve the quality of the evaluation of the pore shape, it was proposed to use a generalized index of the pore shape F, which reflects both roundness and pore isometry. Using the form factor F, the structure of thin macropores was studied in vertical sections from the genetic horizons of the zonal loamy soils of the European territory of Russia. With the help of cluster analysis in the studied soils, 8 types of pore space specific for the main aggregative soil structures were identified. The selected types differ in shape, orientation and size of thin macropores in micromorphological sections. By means of discriminant analysis, a system of automated morphometric diagnostics of the aggregate soil structure based on the structure of the pore space of the soil has been developed. The natural genetic divergence of the aggregate structure in virgin soils and the agrogenic convergence of the structure in the arable horizons of agrosoils are shown. Morphometric criteria for diagnosing the four main stages of the degradation of the physical structure of the soil according to the shape and orientation of the soil pores are proposed.

Based on analyzing the catenary sequence of soils and parent materials down the northern slope of the Klin-Dmitrov Ridge adjacent to the Upper Volga Lowland (formerly the periglacial zone of the Russian Plain), it was revealed that sediments including sandy loams, clay loams and clays, which constituted slope terraces at heights from 130 to 180 m a.s.l. and often accounted for lithic discontinuities in soil profiles, had glacio-lacustrine genesis, i.e., they had accumulated during the existence of a periglacial dammed lake at the final stages of the Late Pleistocene.

Kaolinite suspensions were inoculated by microorganisms (Bacillus velezensis) for 2 months. During the period of inoculation the formation of microaggregates of a certain shape and size was traced by electron microscopy. During the experiment the initially predominant planar structure was partially transformed. The newly-formed large (up to 250 µm in diameter) organo-mineral aggregate-like particles were registered. We suppose that during the 2-month period of incubation B. velezensis microorganisms partially destroyed the crystal structure of minerals to obtain the vitally necessary potassium. The protein compounds produced by bacteria hydrophobized the surface of the minerals which resulted in the formation of organo-mineral aggregates by bonds of hydrophobic-hydrophilic interaction.

This paper describes soil chronosequence studies relating to fertility evolution of meadow-chernozemic (Gleyic Chernozem) soil of the Kuban region. The research has been conducted in the rice irrigation system of Krasnoarmeysky district, Krasnodar Krai. Over the course of 80 years with 12-year intervals, soil was sampled from pits from the plots/checks with permanent rice cultivation, or with crop rotation as well as from fallow land. Changes of morphological, physical and physico-chemical soil characteristics were studied. Rice paddy cultivation results in removal from the plow layer organic substances, carbonates, mineral elements, and silt particles, i.e. of the components responsible for stable soil development in the irrigation system. This illustrates the expression of dehumification, lessivage, and degradation soil processes with rice cultivation permanently as a monoculture or in a crop rotation during the chronosequence study. Deterioration of the soil physical condition is one of ever-increasing factors.

The main indicators characterizing the surface properties of soils formed on the eluvium of Triassic clays of the Kostroma region have been studied. The categories of specific surface area and the degree of soil hydrophilicity have been calculated. Levels of sorption capacity and parameters of ultraporosity of the solid phase of the investigated soils have been identified.

The relationships between the electrical resistivity and the properties of hydromorphic saline soils forming in a humid climate were established. The salinity factor turned out to be the most significant for the value of electrical resistivity compared to soil texture and organic matter content.

The mechanism of disjoining pressure controlling the swelling and water absorption of gel structures for soil conditioning is discussed. Its quantitative description is based on the fundamental ion-electrostatic model of soil water sorption isotherms containing the phase variable of gel swelling degree and specific surface area index of the soil substrate. The model adequately reproduces the s-shape of soil water sorption isotherms in a wide range of water activity from 0.05 to 0.999 depending on the working doses of hydrogels in the range of 0.05-0.3 mass%. Reinforcement of gel structures with amphiphilic dispersed particles increases the effect of disjoining pressure and water absorption.

Saturated and unsaturated hydraulic conductivity as a function of a thermodynamic potential (pressure) of soil water K(P) are investigated in the sandy samples with admixtures of strongly swelling polymer hydrogels (SSPHs) in a wide concentration range from 0.01 to 0.3 %SSPHs. The author's original centrifugation method has been used along with a kinetic model of the water removal process, which enables to determine the function of water conductivity of gel compositions operating in an unsteady state. In saturation state and within the range of low absolute values of soil water pressure |P| = 0.3-20 kPa the SSPHs significantly (2-10 up to 50 times) reduced the hydraulic conductivity in proportion to the dose of a superabsorbent. A heterogeneous layered structure with a layer of pure gel or gel composition 0.1-0.3% SSHP reduces the saturated conductivity by 10-80 times.In the range | P | = 100-3020 kPa, the K(P) function, on the contrary, strongly increased up to 10–20 times under the action of SSPHs. The calculation of K(P) using the Mualem theory disagrees with our experimental estimation, especially in a range of low water content, where such a calculation strongly (up to 100-1000 times) underestimates the values of K(P).

The research investigates thermodynamic characteristics of water-retention capacity in different types of high swelling polymer hydrogels mixed with mineral soil substrates. The use of a combination of methods of equilibrium centrifugation and thermodesorption of soil moisture allowed for the first time to estimate the water-retaining curves and dispersion of gel compositions in the range of absolute values of thermodynamic potentials from 0 to 1 million J/kg. The introduction of hydrogels in concentrations of 0.1-0.3% total weight of the enclosing mineral material leads to a 5-15 fold increase in the total energy of water retention, 3-8 fold increase in water capacity and available moisture range, bringing investigated hydrophysical characteristics of the original sandy substrate at the level of the fertile loamy soils. The new types of acrylic hydrogels with amphiphilic fillers obtained by the author's technology had a greater water-holding capacity and a better structuring effect in comparison with the "Aquasorb" European trade mark. The incorporation of the electrolyte additives in the form of trace elements and ionic silver into the polymer matrix practically does not change the swelling capacity, allowing adding elicitor and antimicrobial properties to these compositions without compromising the effect of water retention.

A statistical assessment of data on the content and spatial distribution of humus in virgin and arable Chernozems on slopes in the south of the forest-steppe zone of the Central Russian Upland was performed. The greatest number of statistically significant differences between arable and virgin Chernozems was found for the upper soil layer (0–20 cm). At the depths of 200–40, 600–80, and 800–100 cm, the differences between these two groups of soils regarding the humus content were statistically insignificant. Data on the spatial distribution of humus in the layer of 00–20 cm indicated that high- and medium-humus Chernozems (>9.0 and 6.00–9.0% of humus) predominate on the slopes under virgin vegetation; medium-humus Chernozems with small patches of low-humus (<4%) Chernozems compose the soil cover of the slopes under arable fields.

Three variants of model soil constructions were created. Variant 1 (control) is made from Aarable horizon (0-18cm); variant 2 (layered construction) is represented by Aarable horizon (0-6cm), lowland peat (6-12cm), sand (12-18cm); variant 3 is a mixture of Aarable horizon, peat and sand in the same mass proportion as in the layered variant (0-18cm). Water retention capacity of Aarable horizon increased in all variants regardless of the location in the profile. Number of macropores increased and number of mezopores decreased in Aarable horizon of control and layered variants. The greatest number of moisture-saiving pores is observed in the peat-containing layers of variants 2 and 3 as a result of 4-year functioning. The lowest content is in the control in all layers.

This study presents the thermal diffusivity vs. water content curves for topsoil, peat, sand and their mixture used to construct the artificial layered soils at the Moscow State University Soil Station. The thermal diffusivity of studied samples varied in a wide range between 9.2×10⁻⁸ m² s⁻¹ for air-dry peat and 9.6×10⁻⁷ m² s⁻¹ for wet sand. The smallest values of thermal diffusivity were obtained for peat, the greatest ones – for sand, and the topsoil demonstrated medium values of thermal diffusivity.

Using membrane ultrafiltration and size exclusion chromatography (SEC), the effect of Cd (II) and Cu (II) ions on the molecular weight distribution of humic acids (HA) in solution was investigated. It was shown that Cu (II) ions, unlike Cd (II), can take part in the formation of supramolecular HA associates (> 10 kDa).

In a three-month experiment influence of different organic amendments (coal humate, peat-gel, biochar) in comparison with mineral ameliorants (NPK and CaCO₃) on chemical and physical properties of soils at different stages of degradation has been shown. Objects of the research were abrazem and podzol soils of technogenic barrens near Monchegorsk city, Murmansk region (Russia). Festuca rubra was used as a test-culture. According to the obtained data, we can conclude that organic applicants may be suitable for remediation of soils, contaminated by heavy metals. Applicants, selected for the experiment, unequally affected the soil properties and the test-culture growth. For the most disturbed and contaminated soils – abrazems –we suggest coal humate and calcium carbonate as the most promising additives for both toxicants' immobilization and preventing bioaccumulation. Biochar and peat-gel in the tested concentration showed a more expressed positive effect on podzol soils with a lower level of contamination. In both soils, abrazem and podzol, biochar favors to the test-culture growth more, than other amendments. The potential advantage of used organic amendments, coal humate and biochar, in contrast to ameliorants is their ability to improve the physical soil properties.

In a ten-year field experiment the technologies of conventional tillage (Plowing) and resource- and soil-saving treatment (No-till and Mini-till) were compared. The pros and cons of the No-tillage in the condition of temperate humid zone on the sod-podzolic soil are shown. The cons are: significant increase of soil density, lower crop biomass, higher weed infestation, an increase of pesticides application. The pros are increased soil moisture storage capacity, potential stability of cereal crop yield and economic benefits on grain production.

In the field experiment there was studied the seasonal temperature regime of the arable layer of sod-podzolic soil under different soil treatment. It was shown that soil treatment (conventional plowing and No-till technology) did not have a significant effect on the topsoil temperature regime. Seasonal and daily temperature variations in topsoil depended on the location of the soil temperature measurement point, on the distance from the windbreak forest belts and on the crop coverage of the soil.

Iron-deficiency chlorosis is a usual routine problem on calcareous carbonated soils of Crimea. Different reasons cause vine chlorosis: soil properties, physiological status of plants and others. It was shown that chlorosis spot in the vineyard has constant location. Chlorosis can be identified visually and instrumentally. In this study, an attempt was made to find the relationship between soil electrical resistance and the spread of vine chlorosis.