Salt neoformations of seaside solonchaks (different in their granulometric composition) of the dried bottom in the southwestern part of the Aral Sea were studied by X-ray fluorescence, electron microscopy, the sedimentation method, and laser diffractometry. The surface layers of soils of sandy and silty clay composition were considerably saline and enriched with CaCO3. The distribution of CaCO3 over the area was quite uniform, indicating relatively similar conditions for its formation during drying. Salt content varied from 3.1 to 5.8% in silty loam soils and 0.4 to 1.2% in sandy soils. Silty loam soils were characterized by the highest salinity level. In addition to gypsum and halite, easily soluble salts were formed in them: eugsterite (2Na2SO4·CaSO4·2H2O), astrakhanite (Na2SO4·MgSO4·4H2O), and mirabilite (Na2SO4·10H2O). The template mechanism of CaCO3 accumulation in soils was revealed. The result of the interaction of CaCO3 with the solid phase of deposits depended on their granulometric composition, which determined the predominant particle size and, accordingly, the number of crystallization centers. Under the conditions of a small number of crystallization centers in sandy soils, the formation of CaCO3 cutans characterized by varying levels of stability and coverage of the sand grain surface occurred. In silty-clay soils with a large number of crystallization centers under constrained conditions for crystal growth, CaCO3 precipitation led to the formation of molecular clusters that bound clay and silty particles into CaCO3 microaggregates. The cause of the increased activity of salt neoformations in the processes of aeolian transport was established. This transport and, therefore, salinization of adjacent territories was facilitated by the blocking of adsorption centers by calcite in clays, which prevented the binding of soluble salts in clay–salt microaggregates.

Soil hydrology has deep Russian roots, which are primarily related to the theory of soil hydrological constants and their practical application. These constants have been used to assess the hydrological soil conditions in stationary observations, for which attempts to arrange regular hydrological observations in the landscape faced impracticable complexity of work and calculations and provided unreliable quantitative predictions. At present, there are new opportunities for experimental research, digital analysis, and prediction of hydrological indicators of soils in the landscape. A new quantitative approach to the use of digital technologies for monitoring soil water and temperature in the soils of agricultural landscapes, their dynamics, and their probabilistic calculations has been developed. Based on the soil map, it is proposed to create an information and measurement system with the studied thermal and hydrophysical characteristics of soils using mathematical models to calculate the dynamics of moisture and temperature for given periods and conditions of different availability of heat and precipitation, which allows us to quantify the availability of moisture reserves in the soils of the agricultural landscape. This system of observations, assessment, and forecast includes the use of modern technologies for determining soil water content and temperature, the adaptation of predictive physically based models for calculating the dynamics of moisture reserves depending on the availability of precipitation and conditions at the lower boundary of soil profiles. The paper deals with the hydrological analysis of soils by the example of the agricultural landscape of the Zelenograd station of the Dokuchaev Soil Science Institute in the village of El’digino, Pushkino district, Moscow oblast.

Complexes of gray forest soils of different podzolization degrees with the participation of gray forest podzolized soils with the second humus horizon play a noticeable role in the soil cover patterns of Vladimir Opolie. The agronomic homogeneity and agronomic compatibility of gray forest soils in automorphic positions (“plakor” sites) were assessed on the test field of the Vladimir Agricultural Research Institute. The term “soil homogeneity” implies in our study the closeness of crop yield estimates (scores) for the soil polygons; the term “soil compatibility” implies the possibility to apply the same technologies in the same dates for different soil polygons within a field. To assess the agronomic homogeneity and compatibility of soils, the statistical analysis of the yields of test crop (oats) was performed, and the spatial distribution of the particular parameters of soil hydrothermic regime was studied. The analysis of crop yields showed their high variability: the gray forest soils on microhighs showed the minimal potential fertility, and the maximal fertility was typical of the soils with the second humus horizon in microlows. Soils also differed significantly in their hydrothermic regime, as the gray forest soils with the second humus horizon were heated and cooled slower than the background gray forest soils; their temperature had a stronger lag effect and displayed a narrower amplitude in seasonal fluctuations; and these soils were wetter during the first weeks (40 days) of the growing season. Being colder and wetter, the soils with the second humus horizons reached their physical ripeness later than the gray forest soils. Thus, the soil cover of the test plot in the automorphic position is heterogeneous; from the agronomic standpoint, its components are incompatible.

Pore-size distribution in a soddy-podzolic silt loamy soil developing from mantle loesslike loam (Eutric Albic Retisol (Loamic, Cutanic)) was calculated from the water retention curve according to Jurin’s equation and directly determined in microtomographic experiments. Rounded macropores with the diameter of their sections from 75 to 1000 μm predominate in horizontal sections if the studied soil samples. A larger part of the soil pores (>30–35%) belongs to micro- and nanopores, and they cannot be quantitatively determined by the tomographic method, because their sizes are smaller than the detection limit of the applied X-ray microtomography (8.75 μm per pixel). This leads to a significantly larger pore volume determined from the water retention curve in comparison with the “tomographic” pore volume. A comparative analysis of pore-size distribution curves obtained by these methods shows that the major regularities of the pore-size distribution in the range from 30 to 5000 μm are similar in both cases. Fine macropores and, partly, mesopores predominate. Common characteristics of the pore-size distribution curves obtained by these methods, including the coincidence of the peaks, attest to the validity of classical approaches, according to which the hydrology of soil pore space can be perceived as a physical model of cylindrical capillaries of different sizes with capillary-sorbed water.

The main advantages of applying computed tomography to studying soil samples include non-invasiveness, independence of the moisture content in the samples and the possibility for mathematical modelling. The methodological problems of this imaging technique include restrictions of the sample size, resolution limitations and segmentation difficulties.

The methods of X-ray diffractometry, scanning electron microscopy, and energy dispersion analysis have been used in the mineralogical study of Baer mound soils in the southern part of the Astrakhan oblast. It has been established that such framework minerals as quartz and feldspars form the basis of the mineralogical composition of soils and mound deposits. It has been shown that the mound topsoils have similar mineralogy along the entire profile. Besides the essentially higher content of layered minerals, the soils at the foot of the mound and in the intermound hollow are characterized by a binomial mineralogical profile. Kaolin, chlorite, illite, illite-smectite, and smectite have been identified in the clay fraction of the soils. The processes of illitization growing down the slope and along the soil profile have been recognized in the soils.

Study of the composition, structure and morphology of microaggregates less than 1 mm in size in soils of one of the Behr hillocks revealed a high share of the clay-salt segregations (microaggregates and cutans). It was established that the segregation type depends on the mud content in soil, while the packing of particles, as well as the size and morphology of microaggregates, depend on the content and properties of salts. The clay component in the microaggregates is mainly represented by smectite. Carbonate (calcitic, dolomitic, and ferruginous) clay-salt microaggregates were found in all horizons of the studied soils, except for horizon Ap on the subhillock plain in the former rice paddy. Gypsum clay-salt microaggregates were identified in the salic horizon Bs of soils. The microaggregates in solonchaks were formed with the contribution of Na-Mg-Ca chlorides and sulfates. The formation of clay-salt aggregates promoted high microstructuring of soils and stability of the Behr hillocks under arid climatic conditions.

New instruments to measure pore space in 3D images (tomography), contact angle, rheological properties, etc. has come to be used in soil science. Those properties and measurements should find their application in soil studies; the soil measurement data obtained with the new equipment is discussed. The new instruments and techniques require major methodological efforts to identify the limits of their applicability, the optimal ranges, measurement conditions, and general standardization of experimental determination procedures.