When studying humate solutions, it is often not taken into account that humic substances (HS) can form supramolecular formations (SMFs) from molecular particles. These SMFs are highly stable, that is, the particles-molecules of HS do not separate from them spontaneously. It follows that at concentrations of the existence of SMFs, it is they, and not the particles-molecules of HS, that should be in solutions and determine their properties. The purpose of the study is to assess the influence of the form of existence of HS in solutions on their physico-chemical properties and biological activity. Solutions of sodium humate from brown coal were used in the work. The experimental results showed that with an increase in the concentration of humates, an abrupt increase in pH in the range of 30–50 mg l⁻¹ is observed. These concentrations correspond to the literature data on changes in the structure of HC in solutions: at concentrations above 30 mg l⁻¹ – barrier concentration – HS molecules form SMFs by self-assembly. Both molecular particles and SMFs, due to the diphilicity of HS, have the properties of surfactants. That is, in solutions at the interface of the “water–air” phases, HS films form. The strength of the films depends on the size of its constituent particles and the speed of their movement from the thickness to the surface of the solution. When plotting graphs in the coordinates “Film formation time in hours–Log humate concentration, mg l⁻¹”, a jump corresponding to the barrier concentration was detected on the curves. It was also found that during foliar treatment of cucumber shoots with mechanoactivated humate solutions with concentrations below the barrier, the stimulation effect increases, apparently due to the transition from the existence of HS in solution in the form of SMFs to existence in the form of particles-molecules that, due to their small size, can penetrate plant cells.

Based on earlier study results, the drying process changes the soil properties and, in particular, the characteristic features of a specific soil organic material such as a humic substance (HS). HS is the basis of soil organomineral gels that cover and bind soil particles. When water is removed from soil, gels are subjected to hydrophobization and compression resulting in changes in properties of soil samples. The recovery of soil gels of air-dried samples should reduce the discrepancy between the study data obtained on the soil properties of dried and non-dried soil samples. The study objective is to find ways to recover the structure of soil gels. Samples of six soil types were studied. Vibration viscometry, laser diffractometry, scanning electron microscopy (SEM), photocolorimetry, and conductometry were used in this work. The drying of soil samples increases the size of supramolecular formations (SMFs) in the soil and reduces the soil paste viscosity, a parameter characterizing the structure and the ability of gels to swell. To recover the structure of soil gels, it is proposed to reduce the size of SMFs from HSs to the initial level. SMFs of air-dried samples were separated by soil moistening and subsequent treatment with various temperatures, by ultrasound, and by freezing. Based on the SEM data, heating and ultrasound treatment do not reduce, but enlarge SMFs. Humidification of air-dried soils, exposure to moisture for two weeks, and subsequent freezing bring the paste viscosity of a number of studied soils closer to the condition of samples that were not dried. This process is due to the return of SMFs to size values of the initial soils, as evidenced by the laser diffractometer data on the suspended particle size distribution. Hence, a method for recovery of gel structures in dried soils to the initial state is proposed.

It is common to consider the experimental soil physics results from the standpoint of a three-phase soil model. Along with the three-phase model, a gel model of soils is used. These models are based on different principles: in the three-phase model, solid phase constancy and liquid mobility; in the gel model, the ability of soil gels to swell, harden, and reduce water mobility. The purpose of this work is to assess the applicability of three-phase and gel soil models to analyzing the study results of some physical properties of soils. The studies were carried out with the zonal soil series: sod–podzolic, gray forest, chernozem, and chestnut soils. The following methods were used in this work: vibration viscometry, laser diffractometry, and electrical resistivity of soils. Unexpected results were obtained in the study of the soil’s physical properties. Firstly, the curve of the relationship between the moisture content of soil samples and the viscosity of pastes prepared from them reached the maximum at the point of limited availability of water (PLAW). Secondly, under the increased mechanical action on soil pastes, the particle size increased rather than decreased in them. Thirdly, the soil electrical resistivity–moisture relationship maintains a uniform course in the PLAW area. Meanwhile, at this water content, the continuous liquid phase framework providing moisture and electrical conductivity disappears in the soils. Fourthly, moist soils dry out in a desiccator over water. It is not possible to explain these results from the standpoint of the three-phase soil model generally accepted in soil science. For this reason, the gel model of soils was used to analyze and explain all the results obtained.

The point of limited availability of water (PLAW) characterizes the lower boundary of the area with the most productive moisture for plants. The analysis of the experimental methods used to determine PLAW is indicative of their high labor intensity and low efficiency. The objective of this study is to develop a high-performance and accurate method to determine PLAW. In the work 18 samples from various soils were used. It is proposed to determine PLAW by the following method: soil samples are placed in a Schott funnel, moistened with excess water, and then water is pumped out using a water jet pump. As water is removed from the sample, the interval between drops falling from the funnel increases. A jump in the intervals between drops is considered as an indicator of experiment completion. According to the experimental results, the soil moisture content obtained by vacuuming correlates with the values calculated for the lowest soil moisture capacity (according to Dolgov) by 87

The effect of alkalinization of fulvic acid (FA) solutions on an increase in their optical density has been studied. To explain this phenomenon, FA particles existing in solutions at different pH have been studied by scanning electron microscopy (SEM) and scanning tunneling microscopy (STM). It has been found that an increase in pH results in a noticeable decrease in the size of the supramolecular assemblies of FA molecules from ~200 to ~100 nm. An STM study of FA samples demonstrates that FAs exist in solutions as supramolecular assemblies of several hundred nanometers in size formed by 10–20 nm FA particle molecules. The observed phenomenon has been explained using the existing ideas about the supramolecular fractal cluster organization of humic substances. The explanation states that the upper layer of F-clusters degrades to give FA particle molecules, while the cluster size is seen to decrease. The FA particle molecules cannot be detected by SEM due to their small size, but they are readily visualized by STM.

Agrolandscape and ecological zoning of natural forage lands (NFL) has been developed at the Williams Federal Research Center of Forage Production & Agroecology for the information support of regionally, landscape and ecologically differentiated agriculture, rational nature management, preservation of soil fertility, and increase of productivity and sustainability of agroecosystems and agrolandscapes. The zoning covers 11 natural and economic (economic) regions of the country, i. e. Northern, Northwestern, Volga-Vyatka, Central, Central Chernozem, Volga Region, North Caucasian, Urals, West Siberian, East Siberian, Far Eastern. The set of documents for agro-landscape and ecological zoning of the NFL for each natural and economic region of Russia includes the following materials: map M 1:2 500 000, legend, database on lands, database on forage lands, database on negative processes, classification of forage lands, classification of deer pastures, strategy and promising ways of agricultural nature management. The NFL zoning was developed on the basis of the Map of Soil and Ecological Zoning of the Russian Federation M 1:2 500 000 elaborated at the MSU Faculty of Soil Science, which is used as a contour and information basis. Numerous cartographic and statistical data, and available literary and stock sources were used for the zoning, which was based on comparative geographical and agro-landscape-ecological methods. The agro-landscape and ecological zoning of the NFL provides zonal, regional, landscape and ecological adaptation and specialization for the development of agriculture, which allows using local natural resources with the greatest efficiency and minimizing the development of negative processes. The databases of the soil-ecological zoning map have been supplemented with new information and indicators characterizing the state of landscapes and their components, such as climate, relief, hydrological regime, soils, vegetation, NFL, the development of negative processes, ecological and economic conditions. This is a significant contribution to the inventory of lands and fodder lands, nature management and protection of agroecosystems and agricultural landscapes. In the future, it is advisable to combine materials and databases of the soil-ecological zoning of the Russian Federation and the agro-landscape-ecological zoning of NFL of different regions of the Russian Federation, created on a single basis, to assess and monitor the state of agrolandscapes, soils and forage lands, and take administrative decisions on nature management in agriculture.

It was previously established that soil drying changes their properties and, in particular, the characteristics of a specific soil organic substance – humic substances (HS). HS is the basis of soil organomineral gels that cover and bind soil particles. When water is removed from the soil, hydrophobization and compression of gels occur, as a result of which the properties of soil samples may change. The restoration of soil gels of air-dry samples should reduce the discrepancy between the data obtained when studying the soil properties of dried and non-dried soil samples. The purpose of the work is to find ways to restore the structure of soil gels. Samples of 6 types of soils were studied. Methods of vibration viscometry, laser diffractometry, scanning electron microscopy (SEM), photocolorimetry and conductometry were used in the work. It has been found that drying of soil samples increases the size of supramolecular formations (SMFs) from the soil and reduces the viscosity of soil pastes, a parameter characterizing the structure and ability of gels to swell. To restore the structure of soil gels, it is proposed to reduce the size of the SMFs from the HS to the initial ones. SMFs separation of air-dry samples was carried out by moistening the soils and subsequent treatment with various influences: temperature, ultrasound and freezing. Using SEM, it is shown that heating and ultrasound treatment do not reduce, but increase the size of the SMFs. Humidification of air-dry soils, exposure to moisture for 2 weeks and subsequent freezing bring the viscosity of pastes of a number of studied soils closer to the condition of samples that have not been dried. This process occurs due to the return of the SMFs size to the values of the initial soils, as evidenced by the data on the distribution of the size of suspended particles on a laser diffractometer. Thus, a method for restoring gel structures in dried soils to the state of the original soils is proposed.

One of the methods to increase the water stability and erosion resistance of soils is the use of structure-forming polymers. It is believed that the mechanism of their action is based on strengthening the bonds between particles of clay minerals. This approach ignores the existence of organomineral gels on the surface of mineral particles, which can affect the effectiveness of polymers. The purpose of this work is to investigate the interaction of a number of structure-formers used to increase water stability and erosion resistance with soil components. In model experiments on the interaction of polymers with soil components, suspensions of humate and bentonite are used. The results are verified on leached chernozem. The effectiveness of polymers is evaluated by the blade method used to determine the water stability of soils, and the interaction of particles in suspensions in model experiments is evaluated by laser diffractometry. It is established that, in solutions of humates with polymers, the size of particles formed in solutions increases with increasing hydrophobicity of the polymers. No such unambiguous relationship is found in bentonite suspensions with polymers. Verification of the results of model experiments on chernozem has shown that the water stability of the aggregates increases with an increase in the hydrophobicity of the polymer used for treatment. To further verify the role of organic matter in ensuring soil water stability, the possibility of using oppositely charged humic substances and iron sol to increase soil water stability is evaluated. The experiments have shown that the use of iron sol increases the water stability of chernozem. Moreover, at an increase in the pH of the iron sol solution from 1.7 to 6.1, the effect value increases from 11 to 59

The response of the microbial community of soils to different levels of oil contamination was studied in a model experiment by the parameters: basal respiration (BR), substrate induced respiration (SIR), carbon of microbial biomass (Cmic), potential denitrification (DNF), methanogenesis, and catalase activity. We analyzed light-chestnut (Haplic Kastanozems Sodic) and meadow-chestnut (Gleyic Kastanozems Chromic) soils of the dry-steppe zone of Stavropol region, differing in the organic matter amount, salinity, and the content of physical clay. The intensity of BR increased within a 30-day-period after the crude-oil input to the soils and caused the growth of Cmic due to activation of oil-oxidizing microorganisms in anaerobic zones of soils. The variations in DNF in light-chestnut and meadow-chestnut soils were in different directions, which was probably related to the organic-matter content and salinity of the soils. The catalase activity was a sensitive indicator of petroleum hydrocarbons in light-chestnut soil, but salinity was the determining factor for its activity in meadow chestnut soil. Biotesting with the use of worms Eisenia fetida showed the inability of test organisms to survive in non-contaminated chestnut soils. The BR and SIR related to it were significant indicators, which did not depend on natural factors in chestnut soils. Catalase activity and DNF are limited by the salinity factor.

In the work, the influence of water content in soil pastes on their viscosity was studied by the method of vibrational viscometry and changes in viscosity were explained from the standpoint of the structural organization of humic substances (HS) of soils. It was found that the viscosity of pastes prepared from sod-podzolic soil, with a decrease in their water content below 36%, increases to values of 4000–4200 MPa sec, and then practically does not change. This contradicted the existing ideas about the viscosity of suspensions, which should continuously increase with a decrease in the water content in them. This phenomenon was explained from the standpoint of the presence in the soil paste another component in addition to water and soil particles (aggregates and microaggregates) – supramolecular formations (SF) from soil HS, which can separate from soil gels and pass into a dispersion medium. According to the literature data, SF of HS exist in soils in the form of fractal clusters (F-clusters) consisting of particles-molecules. Due to the high stability of F-clusters, it is possible to assume that soil particles sliding along F-clusters in pastes, and a change in the thickness of the F-cluster layer through which sliding occurs may not significantly influence the viscosity of soil pastes. The data obtained during the study of the viscosity of soil pastes confirm the importance of F-clusters in the occurrence of soil properties.

A comprehensive quantitative and qualitative characterization of prokaryotic communities of solid atmospheric fallout (dust aerosol) and soils in the areas with different anthropogenic loads within the territory of Moscow was obtained. The total number of bacteria in the studied samples of solid atmospheric fallouts (SAF) was lower than the number of bacteria in soil samples; actinomycete mycelium was not found in dust samples, although it was found in soil samples. The number of culturable saprotrophic bacteria in dust samples was an order of magnitude lower than in Urbic Technosols taken at the same plots. Representatives of the genus Micrococcus dominated the culturable bacteria in the dust aerosols, while representatives of the phylum Proteobacteria dominated in soils. Representatives of the Enterobacteriaceae family were found in the dust samples, among which there were species that are potential human pathogens. The maximum biodiversity of bacteria of the Enterobacteriaceae family was recorded in the dust samples taken in areas with increased anthropogenic and transport load. The sanitary-indicative bacterium Escherichia coli was found in all samples of the dust and Urbic Technosols; its content varied from 10 to 100 CFU/g, which corresponds to the moderate degree of epidemic danger. Ecological indices calculated for prokaryotic communities in situ (barcoding of the 16S rRNA gene) indicate a lower taxonomic diversity of SAF prokaryotic communities in comparison with communities of closely spaced Urbic Technosols.

The opinion exists that water stability is provided by hydrophobic bonds between organic soil particles; however, there are works in which the main role in the occurrence of this property is assigned to the presence of hydrophilic organic substances in soils. The goal of this study is to clarify the nature of the bonds (hydrophilic or hydrophobic) that ensure the water stability of soils. We used samples of sod-podzolic and gray forest soils, as well as leached chernozem. Experiments to assess water stability were carried out using the method of “blades.” It is based on the dissection of linearly arranged aggregates, which were preliminarily moistened in vacuum to values close to saturation. The energy of hydrophobic bonds depends on the temperature; therefore, the influence of temperature on the value of the determined water stability was studied. Experiments showed that, as the temperature increases, the water stability of aggregates stored in the wet state increases from the moment of selection and decreases as the temperature increases. This indicates the leading role of hydrophobic bonds in the formation of water stability. As for the samples dried to an air-dry state, moistened again, and kept wet for more than two weeks, no temperature dependence of the water stability has been found. Taking into account that the strength of hydrophobic bonds increases with increasing temperature, while that of hydrophilic bonds decreases, the obtained data immutability of water stability can be explained if we assume the joint participation both hydrophobic and hydrophilic bonds in water stability of soil samples that have passed through the stage of drying to an air-dry state. In fact, these results indicate a strong change in the structural organization of soils during drying.

The structure and functions of the “Soil-Geographical Database of Russia Information System” (ISSGDBR) implemented on the platform of the Soil Science Faculty of the Lomonosov Moscow State University are considered. The current state of national soil databases and developing on that base international soil information systems are described. The created information system consists of three sections. The first section includes soil maps of different scales and maps of the natural conditions of the territory of the Russian Federation. The second section is represented by a natural-attribute database, which is based on a soil profile with associated analytical characteristics. In the third section, with the help of software tools, the collected varied information about the soil cover becomes the basis for modeling the spatial distribution of various indicators, performing calculations in applied projects for a wide range of users. The ISSGDBR is considered as an expert and analytical center, which acts as a coordinator and supports the functioning of a distributed network, as well as the development and distributing of internationally relevant standards for description, storage, presentation of soil information and data exchange through the use of specialized programs adapted to regional features. In addition, the purpose of the center is the implementation of communication between primary digital resources of natural and soil information localized in various organizations, agrochemical-service regional centers, and federal agencies accumulating information necessary for making managerial decisions.

The effect of alkalinization of fulvic acids (FA) solutions on an increase in their optical density is studied. To explain the observed phenomenon, the investigation of FA particles in solutions with different pH was carried out using scanning electron microscopy (SEM) and scanning tunneling microscopy (STM). It was found that with an increase in pH, there is a noticeable decrease in the size of the observed supramolecular formations from FA from about 200 to 100 nm, and when studying FA samples on STM, it was shown that FA in solutions exist in the form of supramolecular formations several hundred nanometers in size, formed by particles-molecules of FA 10–20 nm. An explanation of the observed phenomenon was proposed based on existing ideas about the supramolecular fractal-cluster organization of humic substances (HS). It consists in the fact that the upper layer of F-clusters disintegrates into particles-molecules of FA with a decrease in their size observed with the help of SEM. At the same time, particles-molecules of FA due to their small size are not visible with the help of SEM, but they are well visualized when using STM.

Based on an analysis of the presumed mechanisms of the hysteresis of the water retention curve (WRC) for soil drying and wetting, as well as the ideas about the nanostructural organization of soils, a conclusion is made that the hysteresis can be caused either by stable (non-colloidal particles) or labile (gels) parts of the solid phase in soils. Due to the fact that until recently the main attention has been focused on study of the effect of the stable solid phase of soils on the hysteresis of the WRC, it is proposed to investigate the effect of soil gels on hysteresis. For this purpose, the effect of the moisture content of soil samples prepared by drying and wetting on the initial viscosity of soil pastes is studied. It has been established that a well-defined hysteresis is observed for the samples of all soil types studied. To explain the hysteresis, two mechanisms based on changes in soil gels in the wetting–drying processes are proposed. One of them is based on the slowness of swelling and shrinkage of soil gels when they absorb and release water. The second is based on the greater hydrophobicity of the surface of gels containing less water, and water slippage on hydrophobic areas of the surface with a decrease in the viscosity of pastes. Thus, the studies conducted have shown that hysteresis phenomena in soils are caused by soil gels and their changes during drying and wetting of soils.

The influence of the contact of chernozem, soddy–podzolic, and gray forest soil aggregates with water on their water stability has been studied. An increase in the contact time of soil aggregates with water leads to a gradual decrease in their water stability. Based on the verified salt solution effect on the water stability of soil aggregates, the water stability of the loss of aggregates in contact with water is not directly proportional to the disjoining pressure. When soil aggregates come into contact with water, fractal clusters of humus particles (F-clusters) are isolated from them. It is suggested that the F-clusters that the soil gel is based on control the physical basis of the water stability of the soil.

Crop exposure to stress during cultivation is known to reduce the yield and to cause the release of allelotoxins from plants into soil. It was assumed that allelotoxin release may considerably affect the vegetable growth in greenhouses and that a decrease in the allelotoxin concentration in greenhouse substrates may improve the plant growth. To verify the assumptions, allelotoxicity and microbial contents were determined in greenhouse substrates in which cucumber, tomato, and pepper plants grew well or poorly. The allelotoxin content was found to be higher and the prokaryote content, lower in the substrates of poorly growing plants. The finding confirmed the assumption that allelotoxins significantly influence the cultivation of vegetables in greenhouses. Treating the plant root zone with humate solutions having a high allelotoxin absorption capacity appreciably improved the cucumber plant growth and was assumed to provide a promising means to increase the vegetable yields in greenhouses.

In Russia, the area of oil-contaminated soils exceeds tens of thousands of hectares. However, to date, there are no unified approaches for evaluation soil change to contamination and the rationing of oil and petroleum hydrocarbons (PHs) in soils. The response of plants in the pot experiment could provide significant results for rationing of PH content in agricultural soils. This work evaluates the response of higher plants as a marker of the direction and intensity of biological processes in soils in the pot experiment under oil contamination to justify the standards of permissible residual content of PH in agricultural soils. The composition and properties of Luvic chernozems, Calcic chernozems, and Voronic chernozems (WRB, 2015) have been investigated in the pot experiment a month later the soil contamination with crude sulfur-containing oil. The effect of different oil doses on the bioproductivity of wheat and pea has been evaluated. In comparison to pea, wheat (in terms of dry biomass) showed higher sensitivity to oil contamination with medium and heavy PH fractions. A nonlinear regression model described by a logistic curve has been applied for rationing the PH content in chernozems. The quality standard values found for wheat biomass are 0.9, 0.4, and 1.0 g/kg of soil for Luvic (humus content ~9.8%, sandy loam texture), Calcic (humus content ~7.6%, clay loam texture), and Voronic (humus content ~12.8%, loam texture) chernozems, respectively. The residual PH content levels found as 30% of soil-functioning change, which corresponded to the risk level of soil degradation, estimated by the soil fertility parameter of dry wheat biomass are 1.2, 0.5, and 1.1 g/kg for Voronic, Calcic, and Luvic chernozems, respectively.

The review considers the basic terms characterizing the accumulation of allelotoxic compounds in soil and justifies the need to study soil allelotoxicity and approaches to reduce its negative impact on plants. As is shown, the main sources forming soil allelotoxicity are plant and microbial exudates and the substances released during the decomposition of plant residues. Different classes of allelotoxic substances and putative mechanisms underlying the transformation of allelotoxins in soil are considered as well as the capabilities and limitations of the available approaches to the assessment of soil allelotoxicity. The presence of allelotoxins is poorly detectable by chemical assays; correspondingly, bioassays are most likely to be the best method for this purpose. Analysis of the published data suggests the approaches to decrease the negative impact of soil allelotoxicity, which rely on a decrease in the concentration or activity of allelotoxins in soil or at the seed–soil interface utilizing fixation of allelotoxins on the applied sorbents or activation of the consumption of allelotoxins by microorganisms.

As is well known from the mid-20th century, films of organomineral gels cover and bind soil particles in soils. Soil contact with water has been shown to lead to water absorption by gels and gel swelling. The change of gel properties in soils should manifest itself in a change in the viscosity of soil pastes. A vibrating viscometer was proposed to use to determine the viscosity of soil pastes. The physical meaning laid down in Einstein’s formula was used to interpret the results. This made it possible to assess the degree of gel swelling by the amount of water that remained capable of moving independently of soil particles, that is, was not included in soil gels (free water). The effect on the degree of swelling of soil gels was studied for (1) the moisture content in soil samples used to prepare soil pastes, (2) the time after adding water during the preparation of soil samples used subsequently to obtain soil pastes, and (3) the sample preparation of soil samples (initial, autoclaved, or dried to air-dry and absolutely dry states and re-moistened) used to obtain soil pastes. Experiments showed that (1) the degree of swelling of soil gels increased with the increasing moisture content in soil samples, (2) a longer time of interaction of soil samples with water led to a greater degree of swelling of soil gels, and (3) different degrees of swelling of soil gels were observed in pastes prepared from soil samples that had the same moisture content, but differed in sample preparation protocol.