The effect of different factors and preparation conditions of monofraction samples from the arable horizon of leached chernozem on soil erodibility and its relationship with soil tensile strength (STS) has been studied. The exposure of samples at 38°C reduces their erodibility by two orders of magnitude. The drying of samples, on the contrary, increases their erodibility. It has been shown that erodibility decreases during the experiment. It has been found that the inoculation of soil with yeast cultures ( Naganishia albida , Lipomyces tetrasporus ) reliably increases the STS value in 1.5–1.9 times. The sterile soil is eroded more intensively than the unsterile soil: at 4.9 and 0.3 g/(m 2 s), respectively. The drying of soil followed by wetting to the initial water content (30%) has no significant effect on the STS value in almost all experimental treatments.

Ammonium nitrogen (N-NH4) concentration in the calcisols of the Nikitsky Botanical Garden shows considerable spatiotemporal variation. This study has shown an extremely close correlation and corresponding linear relationships between nitrogen stores in the different soil layers and the average monthly temperature as well as between the logarithms of N-NH4 concentration values and depth.

It has been shown in experiments in a hydraulic flume with a knee-shaped bend that the rate of soil erosion more than doubles at the flow impact angles to the channel side from 0° to 50°. At higher channel bends, the experiment could not be performed because of backwater. Results of erosion by water stream approaching the sample surface at angles between 2° and 90° are reported. It has been found that the maximum erosion rate is observed at flow impact angles of about 45°, and the minimum rate at 90°. The minimum soil erosion rate is five times lower than the maximum erosion rate. This is due to the difference in the rate of free water penetration into the upper soil layer, and the impact of the hydrodynamic pressure, which is maximum at the impact angle of 90°. The penetration of water into the interaggregate space results in the breaking of bonds between aggregates, which is the main condition for the capture of particles by the flow.

The effect of density of monofraction samples from the plow horizon of leached chernozem on the rupture rate of interaggregate bonds in water has been studied. The rupture rate of bonds has been determined in a hydraulic flume by alternating passive phases of 1–5 min in duration, during which the sample occurs under a nonmoving water layer, with short (15-s long) active phases with a water flow in the flume. Samples have also been tested for tensile strength and water infiltration rate. It has been shown that the rupture rate of interaggregate bonds is related by a hyperbolic law to the soil density and by an exponential law to the rate of water infiltration to the soil. The latter relationship varies within a year and, hence, can be used as reliable parameter for predicting the seasonal dynamics of soil erodibility.

Linear regression equations between the logarithm of the total soil moisture potential and soil moisture content in the hygroscopic moisture range (Landau–Deryagin law) were derived for typical soils from different natural zones of European Russia. From these equations, a compact algorithm was developed for calculating the hydration energy of soils, which increases from 1280 to 10600 J/kg in the following soil series: heavy loamy soddy podzolic soil–heavy loamy gray forest soil–medium loamy light chestnut soil–heavy loamy brown semidesert soil–light clayey solonchak–light clayey chernozem–medium clayey krasnozem. Relationships were revealed between the hydration energy of soils, the specific surface of soils, the content of physical clay in soils, and the concentration of hydrated exchangeably adsorbed ions.

The theoretically derived dependence of the water vapor density (concentration) in the air on the absolute temperature permitted us to use the information obtained by thermogravimetric method for assessing the total potential of water remaining in colloids after drying at different temperatures. A close correlation and corresponding linear relationship fitting the fundamental physicochemical law by Landau–Derjaguin were observed between the logarithm modulus of the total potential of moisture left in soil colloids after drying at temperatures 27–70° and 70–200°C and their moisture. The total potential of water bound by hydrates and crystalline hydrates of substances in the soils varied in the range from–660 to–2394 J/g water, and that of water bound in soil clay minerals varied in the range from–714 to–2814 J/g water (which corresponds to the total soil water pressure of–7140 to–28140 atm.).

The contamination of heavy loamy chernozem by iron, sodium, magnesium, calcium, and hydrogen chlorides (2% of soil mass) decreases soil moisture content ( W , percent of soil mass) in the interval of the soil moisture pressure ( Р ) from 0.0 to–0.6 atm, which indicate soil degradation. In a range of P from–0.2 to–0.6 atm, there is a close correlation between the logarithm of Р module (log| P |) and W and, therefore, a regression relationship log| P W | = | P 0 |– kW , where | P 0 | and k are empirically determined parameters. This relationship is similar to the Landau–Deryagin law. The parameters | P 0 | and k are also in a close correlation, which is described by the regression equation | P 0 | = 29.3k–0.557. At chernozem contamination by chlorides, the | P 0 | and k parameters become smaller, and so they may be used for the evaluation of degradation of chloride-contaminated soils.

The differential water capacity of the main zonal soils of European Russia and Georgia is determined for the first time. This parameter in the A horizon of these soils rises in the sequence soddy-podzolic soil–gray forest soil–brown semidesert soil–chernozem–light chestnut soil–solonchak–krasnozem within the range of hygroscopic moisture and at equal total potential (or tension) of soil moisture. This is related to a rise in the content of physical clay, humus, or water-soluble salts in the soils. Close correlations are revealed between the logarithm of the absolute value of the total moisture potential (tension) and soil moisture content; between the parameters of this correlation and the specific soil surface; and between the specific soil surface and the content of physical clay in the soil.

Statistical analysis of water vapor sorption by light clayey brown forest soil and its elementary particles of different diameters has revealed extremely close correlations and linear relationships between the logarithm of total soil water potential (pressure) and the water contents in the separated particle-size fractions (due to the hydration of exchangeable cations in the diffuse layer near the surface of soil solid phase), as well as between the water content of particle-size fractions and the logarithm of their diameter (due to the differences in the specific surface area and mineralogy of these particles).

An inverse proportional relationship between soil water potential and the differential water capacity of elementary soil particles 1.3–40 μm in diameter in loamy brown forest soil has been identified for the first time. An inverse linear relationship has also been identified between differential water capacity and the logarithm of elementary soil particle size within the range of hygroscopic moisture. A decrease in the diameter of elementary soil particles by more than 10 times (from >20 μm to <2 μm) increases their differential water capacity by almost 10 times. The knowledge of the exponential relationship between the soil water content and the soil water potential within the range of hygroscopic moisture significantly facilitates the determination of differential soil water capacity.

The mathematical analysis of the data on the sorption of vapor moisture by the granulometric fractions of a loamy soil has for the first time indicated that an inverse linear relationship occurs: (1) Between the soil-moisture content and the logarithm of the moisture total potential (pressure) (probably as a result of the hydration of exchangeable cations that form a diffuse layer near the surface of the solid phase); (2) Between the soil-moisture content and the logarithm of the mean diameter of elementary soil particles (probably, as a result of differences in their specific surface determined by various mineralogical compositions); and (3) Between the hydration energy of elementary soil particles and the logarithm of their diameter.

Using a capillary method, it was demonstrated that destruction of the structure of a loamy soil decreases its total moisture capacity on the average by 0.034 g/cm 3 and increases the moisture content (that is not easily accessible to plants) on average by 0.057 g/cm 3 . As a result, the range of moisture that is easily accessible to plants decreases on average by 0.091 g/cm 3 (that is, by 35% from its initial value). The soil structure influences the parameter of the exponential dependence of capillary pressure of the soil moisture on the volume humidity, which allows one to use it as a criterion during the estimation of the structural state of a soil.

It was shown by capillarimetric and dielcometric methods that Linear relationships exist between the capacitance of soils and their volumetric water content. The coefficients of proportionality in these relationships abruptly decreased upon the disturbance of the soil structure: when the volumetric water content of soils decreased by two times, their capacitance decreased by 7–15 pF for soils with a natural structure and by only 1–2 pF for soils with a degraded structure. Therefore, the proportionality coefficients in these relationships could be used as criteria for assessing the structural state of soils.

Установлено, что в актиномицетных комплексах пустынных почв Монголии значительную долю, превышающую долю мезофильных форм, составляют термотолерантные и термофильные актиномицеты. Среди термотолерантных представителей порядка Actinomycetales наиболее распространенными в пустынных почвах оказались организмы, относящиеся к родам Streptomyces, Micromonospora, Actinomadura, Streptosporangium. В опытах с почвенными микрокосмами показано, что термофильные актиномицеты в пустынных почвах растут, развиваются, образуют мицелий, длина которого сопоставима с длиной мицелия мезофильных форм актиномицетов. Молекулярно-биологическое исследование (методы денатурирующего градиентного гель-электорофореза (DGGE) и гибридизации in situ (FISH) образцов остепненно-пустынной почвы свидетельствует о присутствии в них представителей филума Actinobacteria. Согласно результатам, полученным методом FISH, биомасса метаболически активных мицелиальных актинобактерий превышает биомассу одноклеточных актинобактерий в филогенетической группе Actinobacteria прокариотного микробного сообщества пустынных почв Монголии.

It has been established that soil moisture has a significant impact on the activity of chitinolytic microbial processes, rather than pectinolytic processes. The degradation of polysaccharides with an increase in soil moisture in microbial complex markedly increases the role of prokaryotic microorganisms, especially actinomycetes. For the first time, using the FISH method, the amount of detected phylogenetic composition of a metabolically active hydrolytic complex of humus horizons of grey forest and gley and weakly podzolic soil and humus has been estimated depending on the humidity. At optimum moisture, phylogenetic groups Actinobacteria and Firmicutes dominated in the chitinolytic process. An increase in the proportion of proteobacteria is observed with an increase in humidity. The role of gamma- and alphaproteobacteria and actino-bacteria is heightened with the drying of soil in the hydrolytic complex. A quantitative estimate of the rate of degradation of polysaccharides (pectin and chitin) in different types of soils at different levels of moisture is given. The dependence of the phylogenetic composition of an active microbial hydrolytic complex of humus horizons of grey forest and gley, weakly podzolic soils and humus on humidity is revealed.