Dynamics of the dispersity of model soddy-podzolic soils in a long-term lysimetric experiment

Changes in the particle-size composition and specific surface area were considered for soddy-podzolic soils in large lysimeters of the Soil Research Station of Moscow State University, which simulated anthropogenically modified soils with different sequences of genetic horizons in a long-term (1961–2002) experiment. Changes were detected in the degree of dispersion of the soil horizons occurring under conditions inadequate for their genesis: a decrease in the clay content by 7% and in the external specific surface area from 28.9 to 7.4% in the illuvial horizon placed on the surface and the accumulation of colloidal mineral fractions in the Ap horizon buried at a depth of 80–100 cm. The degree of change depended on the occurrence depth of the buried horizons and increased with approaching the surface. The changes in the dispersity of the model soddypodzolic soils in the lysimetric experiment were primarily due to the translocation of the fine fractions with vertical water flows. The long-term experiment carried out under completely controlled conditions showed that, at the initial functioning stages of the soils with anthropogenically modified profiles, this process was well detectable and significant for the monitoring studies.     

Aggregate Structure of Native and Arable Soils of Different Geneses: Morphological and Rheological Characteristics

Eurasian Soil Science - Aggregates and capillary-saturated pastes from loamy soddy-podzolic soils (Albic Glossic Retisol (Lomic, Cutanic)), typical and vertic chernozems (Haplic Chernozems (Loamic,...     

Thermal diffusivity of plowed leached meadow-chernozemic soils in the Adygeya Republic

Thermal diffusivity of the upper horizons of leached meadow-chernozemic soils varies in dependence on the soil water content within the following limits: 1.20–4.11 × 10⁻⁷ m²/s for the Ap horizon, 1.21–3.85 ×10⁻⁷ m²/s for the A1 horizon, and 1.35–3.73 × 10⁻⁷ m²/s for the A1B horizon. The relationships between the thermal diffusivity and the soil water content are described by S-shape curves with a long gently inclined segment within the range of water contents of <0.20 cm³/cm³, a distinct rise in thermal diffusivity within the water contents from 0.20 to 0.30–0.35 cm³/cm³, and a flattened or somewhat declining segment in the area with the high (>0.30–0.35 cm³/cm³) water contents. The thermal diffusivity of air-dried soil samples correlates with the physical clay (<0.01 mm) content. The Pearson correlation coefficient for these two variables equals −0.67 and is statistically significant at the significance level of 0.05. Regression equations allowing one to calculate the thermal diffusivity of the investigated soil horizons on the basis of data on the soil water content have been obtained.     

S.A. Vladychenskii as a teacher

In the paper “Training of Soil Scientists” published in the journal Pochvovedenie in 1966, S.A. Vladychenskii noted problems that are particularly topical in our days. How to balance pedagogical and research activities at the institutes of higher education? What should be done to improve the quality of teaching? What are the requirements for teachers and professors of soil science? What is the optimum level of specialization in their selected field for students? In this paper, we consider current problems of teaching soil science at the institutes of higher education in the context of the ideas advanced by S.A. Vladychenskii.     

The study of preferential water flows and convective heat transfer using the method of temperature labeling

The proposed method of temperature labeling makes it possible to study the convective heat transfer by fast water flows. A filtration experiment on the transfer of heated moisture in the plow layer of a light loamy soddy-podzolic soil of Moscow region has been performed. The high unevenness of the front of the water migration in the experiment is related to the spatial distribution of the major pores and leads to sharp changes in the soil temperature. Temperature measurements in large lysimeters of Moscow State University filled with soddy-podzolic soils indicate that there are short periods of rapid changes in the soil temperature during the snowmelt season and upon heavy showers. These changes are related to intense gravitational water flows. In the soils with a distinct blocky structure of the upper horizon, the convective transfer of heat is better expressed than that in the soils with a crumb or granular structure of the plow layer.     

Microstructure of Soils of Different Geneses and Its Transformation in Constructozems of Moscow

The transformation of microstructure of constructozems was studied in a four-year-long (2012–2016) field experiment with the use of rheological and electron microscopy methods. Field studies were performed in the area of Moscow State University on three variants of artificial human-made soils (constructozems) differing in the structure of their profiles: (1) the control variant with the upper part composed of a homogenized Ap horizon, (2) the layered constructozem composed of a sequence of layers (Ap–peat–sand–Ap), and (3) the constructozem consisting of a mixture of the above-mentioned horizons. Electron microscopy attested to an increase in differentiation of the pore space in the upper Ap horizons in variants 1 and 2: new pores and chambers of different sizes appeared. In the loose porous mass of the peat layer in variant 2, more compact cohesive microstructures were formed. Microaggregation was identified in the upper layer of variant 3. Changes in the spatial arrangement of the solid phase of the soils were reflected in their rheological properties. A gradual increase in stability of structural bonds in the Ap horizon (variant 1) was detected. In variant 2, the underlying peat layer affected the shape of rheological curves in the Ap horizon. In variant 3, changes in strength properties of the mixed soil mass resulted in the formation of rheological behavior of fluid bodies typical of the plowed humus horizons.     

Structural status of technogenic soils and the development of preferential water flows

A technogenic soil (technozem) created on the surface of the former sludge pond of the Lebedinskii iron-ore quarry in the course of land rehabilitation was studied. The upper chernozemic fill in the technozem was underlain by the sandy or loamy layers. The water regime of this soil differed from the water regime of background automorphic natural soils and was characterized by a periodic stagnation of water at the boundary between the two layers. In 20 years, this type of the water regime resulted in the development of a columnar structure in the lower part of the chernozemic layer. The coatings on ped faces in this part of the profile had an increased content of Fe and Ca ions, and the soil texture became coarser under conditions of the alkaline medium. There was no differentiation of the carbon of organic substances and carbonates in the soil profile. Field studies of water flows in this soil with the use of starch label and laboratory experiments on infiltration of salt solutions through the soil columns with determination of ion concentrations in separate portions of the filtrate demonstrated the existence of preferential water flows in the technozem. Rapid infiltration of water through preferential water paths in the chernozemic layer after abundant rainfalls and during the snowmelt season leads to the development of perched water above the textural boundary. Temporary water stagnation in this zone ensures an increased water content in the intraped mass of columnar peds in the lower part of the chernozemic layer.     

Sensitivity assessment,adjustment, and comparison of mathematical models describing the migration of pesticides in soil using lysimetric data

The water block of physically founded models of different levels (chromatographic PEARL models and dual-porosity MACRO models) was parameterized using laboratory experimental data and tested using the results of studying the water regime of loamy soddy-podzolic soil in large lysimeters of the Experimental Soil Station of Moscow State University. The models were adapted using a stepwise approach, which involved the sequential assessment and adjustment of each submodel. The models unadjusted for the water block underestimated the lysimeter flow and overestimated the soil water content. The theoretical necessity of the model adjustment was explained by the different scales of the experimental objects (soil samples) and simulated phenomenon (soil profile). The adjustment of the models by selecting the most sensitive hydrophysical parameters of the soils (the approximation parameters of the soil water retention curve (SWRC)) gave good agreement between the predicted moisture profiles and their actual values. In distinction from the PEARL model, the MARCO model reliably described the migration of a pesticide through the soil profile, which confirmed the necessity of physically founded models accounting for the separation of preferential flows in the pore space for the prediction, analysis, optimization, and management of modern agricultural technologies.     

Hydrosorption and Microstructural Characteristics of Soil Horizons of Different Geneses and Their Change in Constructozems

Eurasian Soil Science - Soil substrates used in model constructozems (artificially constructed soils) of different fabrics created on the territory of Lomonosov Moscow State University in 2012 were...     

Thermal diffusivity and temperature regime of soils in large lysimeters of the experimental soil station of Moscow State University

The thermal diffusivity of the upper horizons of model soddy-podzolic soils in the lysimeters depends on their water contents and varies within 2.1?4.32 × 10^?7 m²/s in the Ap horizon, 1.59?3.99 × 10^?7 m²/s in the B1 horizon, 1.28?3.74 × 10^?7 m²/s in the plowed B2 horizon, and 1.12?4.10 × 10^?7 m²/s in the B2 horizon. The dependence of the thermal diffusivity on the soil water content is described by an inverted parabolic curve for the Ap horizon, an S-shaped curve for the B1 and B2 horizons, and by a curve of transitional type for the plowed B2 horizon. The temperature regimes of model soils with different morphologies of the profile do not differ much and are close to the soil temperature regime under natural conditions on the plots of the weather station of Moscow State University.