A complex of soils characteristic of the Vladimir Opole region was studied: agro-gray typical deep-arable soil, tongue-shaped agrozem and agro-gray gleyic soil. The high contrast of soil properties, which is due to the genesis of field landscapes, can be traced in the differences in the arable and subarable horizons of agro-gray soils at the aggregate and microaggregate levels. The soils have an excellent structural condition, high water resistance and mechanical strength of aggregates. In the aggregate structure of arable horizons, dependences on the position in the relief were found: down the slope the content of agronomically valuable aggregates decreases, the weighted average diameter of aggregates increases, the water resistance of aggregates and the mechanical strength of aggregates at capillary saturation decreases. However, the distribution and size of microaggregates, as well as the strength of aggregates in an air-dry state, reflects the complex genesis of the landscape and retains the influence of paleorelief with depressions and elevations. The weighted average diameter of microaggregates of arable horizons of the soils of the Vladimir Opole region is close to the chernozems of the Kursk region. The granulometric composition of the studied soils is typical of Vladimir Opolye soils and close to each other. In accordance with the classification of N.A. Kachinsky arable horizons are medium loamy, coarse silt, BT horizons are heavy loamy, coarse silt. The most structural is the arable horizon of agro-gray typical deep-arable soil, it has large microaggregates, it also has high water resistance and the highest content of agronomically valuable aggregates. The most homogeneous in terms of aggregate composition is tongue-shaped agrozem; the average diameter of aggregates and microaggregates in the arable and subarable horizons are equal and similar in the content of microaggregates and agronomically valuable aggregates. This soil is also highly water resistant. Agro-gray gleyic soil contains fewer agronomically valuable aggregates and its water stability is unsatisfactory.

The results of rheological studies of semihydromorphic soils of taiga zone in the northeast of the European part of Russia (Komi Republic) on a modular rheometer MCR-302 (Anton Paar, Austria) by an amplitude sweep test (oscillatory method) are considered. Rheological studies of soil samples have been performed with plate–plate measuring systems at maximum capillary water saturation. The strongest interactions between soil particles develop in the horizons with the high content of mobile humus compounds (fulvic acids) and Al–Fe-humus complexes (ELhi,g–ELg–CRM horizons). Increased structural stiffness is due to the binding of soil particles with humus substances and Al–Fe-humus complexes with the development of strong interparticle bonds. Freezing–thawing processes are an important factor of changes in rheological parameters. The impact of seasonal freezing on the rheological behavior is most clearly pronounced in the profile of semihydromorphic svetlozems (Histic Gleyic Stagnosols) in their cryometamorphic (CRM) horizons, where increased stiffness of interparticle bonds is due to condensation compaction of soil particles in the course of the long-term development under temperatures close to 0°С (zero curtain). With an increase in the soil moistening, disaggregation of the mineral mass takes place, which is seen from a significant increase in the plasticity range. Disaggregated soils are more susceptible to erosion, but a thick moss–peat layer forming in the upper part of the profile of semihydromorphic soils protects them from degradation. In the northward direction, from the texturally differentiated soils of southern taiga to the cryomethamorphic soils of forest-tundra, the stiffness and brittleness of interparticle bonds increase, which is associated with a more active input of fulvic acids, including Al–Fe-humus complexes, as well as with a longer freezing of northern soils. It is shown that rheological parameters can be used as additional indicators in the diagnosis and classification of taiga soils.

Проведен сравнительный анализ результатов реологических исследований образцов почв методом амплитудной развертки (amplitude sweep test – AST) на модульном реометре MCR 302 (Anton Paar, Австрия). Объектом исследований послужила подзолистая с микропрофилем подзола супесчано-/тяжелосуглинистая почва на покровном суглинке (Folic Albic Retisol (Abruptic, Loamic, Protospodic)) – почва средней тайги (Республика Коми, окрестности г. Сыктывкара). Реологические параметры определялись на образцах нарушенного (растертые и просеянные через сито) и ненарушенного (монолиты) сложения в состоянии капиллярного увлажнения. Это позволило выявить схожий характер реологического поведения и определить специфику отдельных генетических горизонтов. Наиболее устойчив к механическим нагрузкам верхний органогенный горизонт – лесная подстилка (О). Переходный горизонт BEL характеризуется жесткой, но наименее устойчивой структурой с узким диапазоном деформационных возможностей. Ненарушенные образцы имеют прочные и жесткие структурные связи в области вязкоупругого поведения, что обусловлено плотной упаковкой и многоуровневым взаимодействием почвенных частиц, микроагрегированностью и присутствием фрагментов корней. Повышенная жесткость сложения монолитов сочетается с хрупкостью их структуры. Нарушенные образцы при нагрузке характеризовались большей пластичностью по сравнению с монолитами, что обусловлено разрушением агрегатов в процессе растирки и образованием большого количества межчастичных контактов.

We have studied mechanical characteristics of soils of Syktyvkar of the same genesis and different land use: agrosoddy–podzolic urban-stratified soil within the city, park postagrozem, and suburban podzolic soil. Their relationship with the organic-matter content and particle-size composition is analyzed. Strength properties are mainly related to the content of coarse fractions (>0.25 mm) in agrosoddy–podzolic urban-stratified soil and to the organic matter content in podzolic soil. Soils are arranged in sequences according to rheological parameters. The strength of structural bonds estimated by the parameter of initial elasticity modulus is the greatest in podzolic soil, and horizons of agrosoddy–podzolic urban-stratified soil are characterized by a wide range of linear viscoelastic status. The starting point of the viscous flow region is the same for postagrozem and podzolic soil.

In this article we describe the use of novel aqueous polymer formulations for stabilization of sand and soil against wind erosion and retention of water in polymer-treated sand/soil samples. Two series of formulations were prepared. The first consisted of polyacrylic acid (PAA) and two electrostatic complexes of PAA with cationic poly(diallyldimethylammonium chloride): negatively and positively charge; the second included PAA-based cross-linked copolymer (PAA#) which forms microgel particles upon swelling and two its electrostatic complexes with the polycation: negatively and positively charged. 1 mass% formulations showed the stability against aggregation for 3 months excepting the negative complex with PAA which aggregated within half an hour after preparation. The viscosity of 1 mass% formulations, which lies within a (1.6÷320)×10−6 m2/s interval, allowed their deposition over fine-grained sand and loamy sand soil using a conventional spray machine followed by formation of polymer-sand(soil) crusts. Both for sand and soil, the PAA#-based crusts demonstrated a higher resistance to mxechanical loads in comparison with the crusts formed by linear PAA: up to a 42.5 MPa mechanical strength for sand/PAA# crust against a 12.5 MPa strength for sand/PAA crust. Additionally, the PAA#-based crusts was not impacted by airstream, up to a 190 km per hour air speed, while PAA-based crust was destroyed within a minute. Finally, PAA# alone and its negative complex were characterized by a high swelling (degree of swelling up to 195) that allowed them to maintain a high water retention capacity, being bound to sand and soil. The results are promising for preparing anti-erosion and water-saving formulations, especially in areas with insufficient moisture content, and design of sand-based composite materials.

The sessile drop method was used to measure the contact angle of wetting (CA) of ordinary Chernozem from the fields of the Kamennaya Steppe agrolandscape used in various ways. The treatments differ in the intensity of tillage operations (protected mowed steppe, arable land after moldboard plowing), the use of mineral fertilizers and their aftereffect, as well as changes in soil properties under the influence of irrigation. At the same time, the total organic carbon content, C/N ratio, specific surface area, and rheological parameters were determined for the physical and chemical characteristics of soils. The results of the study showed that the hydrophilic-hydrophobic properties of the surface of the solid phase of soils, which largely determine the main structure-forming properties of soils, can be characterized by the value of the wetting edge angle. The CA of the studied soil samples varies from 32 degrees (highest wettability) to 45 degrees (lowest wettability). The lowest wettability is due to the increased content of hydrophobic compounds in the organic matter of soils and is characterized by the highest CA and is typical for native, untreated soil of the mowed steppe, which differs from other studied variants of the experiment in all explored physical and chemical parameters. Moldboard plowing as well as fallowing lead to changes in the physical and chemical properties of the soil and the qualitative composition of organic matter in the direction of their deterioration and a decrease in the CA. The use of mineral fertilizers contributes to the increase in the studied indicator mainly due to changes in plant productivity, in particular, the differences in CA are due to the impact of root secretions and plant residues on the soil properties. For the studied soils, the CA changes in the following series: mowed steppe > arable land with the mineral fertilizers application > arable land undergone the aftereffect of fertilizers. Correlation analysis revealed the relationship of CA with organic carbon content, specific surface area, and rheological characteristics of Chernozems. Thus, CA can serve as an integral indicator of changes in the physical and chemical properties of soils, their degradation changes under the conditions of different agricultural load. The method used in this research for determining CA requires a smaller amount of sample compared to rheological methods and is generally more informative than determining the content of organic matter.

Interpolyelectrolyte complexes of a linear cationic polymer poly(diallyldimethylammonium chloride) and anionic microgel particles with carboxyl groups in a pH 6 buffer solution are presented. Dispersions of the microgel and its complexes-negatively charged with a 3-fold molar excess of the anionic groups of the microgel and positively charged with a 3-fold molar excess of the cationic groups of the polycation-retain aggregative stability for six months. When applying 1 wt % dispersions of the microgel and complex on the surface of the soil with a high sand content, polymer-soil coatings with a mechanical strength of 19 to 61 kg/m(2) depending on the composition of the dispersion are formed. These indicators significantly exceed those for coatings obtained by applying a 1 wt % solution of a linear anionic polymer, poly(acrylic acid), on the soil surface. Coatings involving microgel and its complexes remain stable at an air flow rate of 190 km/h.

The preparation of electrostatic complexes between a cationic polymer, poly(diallyldimethylammonium chloride), and natural polyanions, potassium humates, is described. The polycomplexes remain stable in the aqueous solution for a long time (up to 3 months) or form precipitates that can be easily resuspended when the sample is shaken. When aqueous solutions/suspensions of polycomplexes are applied on the sand surface, polymer-sand coatings (crusts) are formed, the mechanical strength of which increases with increasing content of poly(diallyldimethylammonium chloride) in the polycomplex. The greatest resistance to water (water resistance) is exhibited by crusts with a high proportion of mutually neutralized sections of both polymers. For such crusts, sand loss during watering is in the range from 0 to 2%. The developed multicomplex formulations can be used to stabilize soil and ground against water and wind erosion.

Soil pastes at the water content corresponding to the maximum swelling of samples from different genetic horizons of cryometamorphic soils―surface-gleyic iron-illuvial svetlozem (Folic Albic Stagnosol) and peaty and peat humus-impregnated gleyic svetlozems (Histic Gleyic Stagnosols)―have been studied with an MCR-302 modular rheometer (Anton Paar, Austria). It has been found that the strongest interparticle bonds are formed in the horizons of cryometamorphic soils characterized by high contents of humic substances and organomineral Al–Fe–humus compounds. These are horizons of podzol microprofile (Eg and BHF) in iron-illuvial svetlozem and a humus-impregnated horizon (ELhi,g) in peaty and peat svetlozems. Organomineral Al–Fe–humus compounds, as well as the seasonal freezing of soils, determine the elastic-brittle character of interparticle interactions. The contents of clay fractions, exchangeable bases, and organic and organomineral substances impart viscoelastic properties to these contacts. An enhancement of elastic-brittle properties of soil is observed under the impact of gleying and freezing. The threefold decrease of the structural interaction parameter (∫ Z ) when going from automorphic to semihydromorphic conditions indicates a decrease in the resistance of peaty and peat svetlozems to mechanical loads under increasing hydromorphism compared to iron-illuvial svetlozems.

Coupled studies of pore space and rheological behavior of undisturbed samples from soddypodzolic soils (Albic Glossic Retisols (Loamic, Aric, Cutanic)) of Moscow oblast under forest and under cropland and from typical chernozems (Haplic Chernozems (Loamic, Aric, Pachic)) of Kursk oblast under oak forest, shelterbelt, and cropland were conducted. Soil pore space was investigated using a Bruker SkyScan 1172 G (Belgium) microtomograph, and 3D models of pore space were constructed. The total pore space (in percent of the volume of analyzed samples) and the volumes of open and closed pores were determined from these models. The nondestructive tomographic method made it possible to analyze the rheological properties of soils for the same samples using the amplitude sweep method on an MCR-302 (Anton Paar, Austria) rheometer. The following parameters of the rheological behavior were determined: storage modulus in the range of linear viscoelastic behavior, the range of linear viscoelastic behavior, and the range of plastic behavior. A joint analysis of the rheological properties and morphometric characteristics of the undisturbed samples of soddy-podzolic soils and chernozems demonstrated the dependence of the rheological behavior of these soils on their physicochemical properties and pore space structure reflecting the differences in the genesis and physical and chemical properties of soil horizons. The correlation analysis attested to direct (positive) relationships between the values of the total and open tomographic porosities, the range of linear viscoelastic behavior, and the deformation upon the destruction of soil structure. Negative relationships were found between the values of open and total porosity and the structural strength of the soil monoliths. A hypothesis about an increase in the range of plastic behavior of soils and a decrease in the strength of soil structure with an increase in porosity was suggested.

The paper discuss the literature data on clay mineralogy of vertisols and presents the investigation of clayey soils formed in ultra-continental climate in the Eravna depression (Buryatia). Soils are formed on the watershed and shoulder positions of the local ridge and are underlined by permafrost. Morphological analysis of soils revealed a combination of cryogenic features (permafrost wedges and cracks, cryogenic structure, above permafrost gleyization) and vertic properties (slickensides, wedge-shaped aggregates). According to the morphology, the soils were classified as Dark compact soil or Gleyic Vertisol Glossic Gelistagnic on the shoulder position, and as Chernozem-like weakly compacted cryoturbated soil or Vertic Gleyic Phaeozem Glossic Pachic Clayic Gelistagnic on the watershed where vertic features were weakly expressed. According to physical properties and clay mineralogy, the shrinking-swelling potential of the soil on the watershed is comparable to the soil of the shoulder: almost the same, and in some horizons even higher content of clay (up to 76%), fine clay (up to 54%) and swelling components in the fine clay (

With the help of computed X-ray microtomography with a resolution of 2.75 μm, changes in the microstructure and pore space of aggregates of 3 mm in diameter from the virgin soddy-podzolic soil (Glossic Retisol (Loamic)) in the air-dry, capillary-moistened, and frozen states after five freeze–thaw cycles were studied in a laboratory experiment. The freezing of the samples was performed at their capillary moistening. It was shown that capillary moistening of initially air-dry samples from the humus (AY), eluvial (EL), and illuvial (BT1) horizons at room temperature resulted in the development of the platy, fine vesicular, and angular blocky microstructure, respectively. The total volume of tomographically visible pores >10 μm increased by 1.3, 2.2, and 3.4 times, respectively. After freeze–thaw cycles, frozen aggregates partly preserved the structural arrangement formed during the capillary moistening. At the same time, in the frozen aggregate from the AY horizon, the total tomographic porosity decreased to the initial level of the air-dry soil. In the frozen aggregate from the EL horizon, large vesicular pores were formed, owing to which the total pore volume retained its increased values. The resistance of aggregate shape to the action of freeze–thaw cycles differed. The aggregate from the EL horizon completely lost its original configuration by the end of the experiment. The aggregate from the AY horizon displayed definite features of sagging after five freeze–thaw cycles, whereas the aggregate from the BT1 horizon preserved its original configuration.

The rheological properties of typical chernozem were investigated by the amplitude sweep test on an MCR-302 rheometer (Anton Paar, Austria) for three water contents: maximum swelling, the liquid limit, and capillary rupture. A method is proposed for determining the water content of capillary rupture on an analyzer by using the curves for soil drying at constant temperature, determined simultaneously with the water content. Comparison of rheological soil characteristics at different soil humidity has shown that variations in the forms of soil water cause changes in the rheological soil behavior from viscous to elastic–brittle.