Dynamics of ecological and biological characteristics of soddy-podzolic soils under long-term oil pollution

The dynamics of respiratory and enzyme activities and toxicological properties of loamy-sandy and loamy soddy-podzolic soils (Retisols) under the long-term influence of oil pollution were studied. The concentrations of the pollutant, at which the activity (the ability of self-purification) of the indigenous soil microflora is preserved, were determined. The dynamics of the decrease of oil product content and the time of elimination of the toxic effects on higher plants at the initial pollutant contents were revealed. The parameters of the respiratory and enzyme activities in the course of the 365-day experiment showed that the microbial community of the loamy-sandy soil was more sensitive to oil pollution. The phytotoxic characteristics of the oil-containing loamy-sandy and loamy soils did not correlate with their respiratory and enzyme activities. This fact testifies to some differences in the mechanisms of their influence on living organisms with different organizational levels and to the necessity of taking into account a complex of parameters when assessing the state of the soils under the long-term effects of oil and its products.     

Dependence of the aggregate swelling parameters in soddy-podzolic soils on their properties

The degree and rate of the aggregate swelling in loamy sandy, loamy, and clayey soddy-podzolic soils of northwestern Russia have been measured using the methods of image analysis. The results of the study have shown that the degree of swelling of the soil aggregates depended on the proportions of the fine (0.005 mm) and sandy fractions, and the rate of the swelling depended on the density of the soil solid phase. A reliable effect of the soil organic matter content on the swelling rate of the studied objects has been established. The aggregates of the arable soddy-podzolic soils with the highest content of organic matter, as well as the aggregates of the native soils, have been characterized by the lowest swelling rates. A method has been developed for the determination of the swelling rate of soil aggregates that has enabled the assessment of the soil structure. The regression dependences of the degree and rate of the aggregate swelling on the properties and composition of soddy-podzolic soils have been plotted.     

Calculating the density of loamy sandy soddy-podzolic soils from penetration resistance diagrams

The possibility for the calculation of the soil bulk density from two-dimensional penetration resistance diagrams drawn using a penetrometer during the vertical sounding of the soil has been discussed. A method has been proposed for calculating the bulk density of loamy sandy soddy-podzolic soils from the soil penetration test diagrams. The model for the calculation of the soil bulk density is based on the general physical concepts with the involvement of similarity theory methods. The adequacy and quality of the model have been studied statistically. The model has been found to be suitable for calculating the bulk density of loamy sandy and sandy podzolic soils.     

Sorption and migration of zinc in taiga zone soils in laboratory and field experiments

The parameters of the zinc sorption and migration were experimentally determined under laboratory and field conditions for soils of forest and meadow biogeocenoses of Tver?? oblast. Two methods gave relatively close values for the parameters of the metal??s sorption by an almost neutral loamy sandy soddy soil of a meadow biogeocenosis. The potential capacity of an acid sandy loamy soddy-podzolic soil for zinc sorption determined under laboratory conditions was not completely realized under the field conditions, which was related to the properties of the biogeocenosis (the forest plants, the organization of the soil pore space, and the soil reaction) and the experimental conditions.     

Changes in the distribution of chemical elements throughout the profile of a soddy-podzolic soil after the long-term application of sewage sludge

The distributions of the total and water-soluble macro- and microelements throughout the profile of a loamy sandy soddy-podzolic soil were studied six years after the long-term (for more than 15 years) application of sewage sludge and lime as ameliorants. It was shown that the anthropogenic factor affecting the distributions of the metals in the soil remained predominant. The highest differences compared to the control were observed for P, S, Cl, Cu, Zn, Ni, and Pb. A second accumulative soil horizon was developed, which was an additional source of contamination with mobile metals for the adjacent environments. Six years after the cessation of the application, the contents of Cu, Zn, and Ni exceeded their PPCs for sandy and loamy sandy soils.     

Factors of the development of taiga and tundra soils with differentiation of Fe and Al oxides in the profile

Statistical data on the bulk contents of iron and aluminum oxides in iron-depleted and iron-enriched horizons of a wide range of taiga and tundra soils were compared. It was found that the soils could be arranged into the following sequence characterized by an increase in the relative contribution of iron oxides and a decrease in the relative contribution of aluminum oxides to the differentiation of sesquioxides in the soil profiles: sandy podzols—soddy-podzolic soils—loamy micropodzols and iron-illuvial svetlozems—cryogenic ferruginated gleyzems. It was concluded that the bleaching of eluvial horizons and the depletion of sesquioxides from them, as well as the accumulation of sesquioxides in the illuvial horizons, are controlled by different processes in different soils. In sandy podzols, the differentiation of sesquioxides is due to the Al-Fe-humus podzolization; in loamy micropodzols and iron-illuvial svetlozems, due to the redox-Al-Fe-humus podzolization; in podzolic and soddy-podzolic soils, due to the selective podzolization and lessivage; and, in cryogenic ferruginated gleyzems, due to the reduction-oxidation processes.     

Changes in the rheological properties and density of a loamy sandy soddy-podzolic soil under the impact of a wheel tractor

Theoretical investigations and field tests have revealed the tendencies of the rheological properties and density of a loamy sandy soddy-podzolic soil under the impact of a wheel tractor. The rheological properties of the soil in the viscoelastic state have been described by a differential equation of the first order relating the compressive stresses with the variation rates of the compressive stresses and the relative vertical compressive deformation. The effect of the dynamic loads at the vertical vibration of a wheel tractor has been mathematically simulated. A method has been proposed for calculating the rheological properties and the soil compaction parameters under a running tractor that considers the effect of the variations of the dynamic load on the soil. Software products have been developed to implement this method. The effect of the main factors on the rheological properties of the soil and its compaction parameters under the impact of a tractor has been quantified.     

Paleosols buried under kurgans of the Pit-grave culture in the steppe zone of the Cis-Ural region

The analysis of soil chronosequences developed from loamy and loamy sandy substrates and buried under kurgans dating back to the Pit-grave archaeological culture in the steppe zone of the Cis-Ural region demonstrated that it is possible to trace the dynamics of the soil properties and to perform paleoclimatic reconstructions for different intervals within the studied period. The properties of sandy soils changed more rapidly than the properties of loamy soils. For sandy soils, notable changes in their properties were revealed in the soil chronosequences dating back to the particular stages of the Pit-grave culture; for loamy soils, such changes could only be traced for the soils buried under the kurgans dating back to different stages of the Pit-grave culture.     

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.     

Evaluation of the Migration Capacity of Zn in the Soil–Plant System

The mobility and migration capacity of Zn in the soil-plant system were studied in a series of pot experiments with barley as a test plant. The parameters of Zn accumulation depending on the metal concentrations in soils and soil solutions were estimated by soil and water culture methods. Experiments with barley in water culture were performed on a nutrient (soil) solution extracted from soddy-podzolic soil (Albic Retisol (Loamic, Ochric)) to which Zn²⁺ was added to reach working concentrations increasing from 0.07 to 430 μM. Different responses of barley plants to changes in the concentration of Zn in the studied soil were identified. Ranges of the corresponding concentrations in the soil and aboveground barley biomass were determined. Parameters of Zn accumulation by test plants were determined depending on the metal content in soddypodzolic soil and the soil solution. A new method was proposed for evaluating the buffer capacity of soils with respect to a heavy metal (Zn) using test plants (BCS(P)_Zn). The method was used to evaluate the buffering capacity of loamy sandy soddy-podzolic soil. The considered methodological approach offers opportunities for using data obtained during the agroecological monitoring of agricultural lands with heavy metals (HMs), including the contents of exchangeable HMs and macroelements (C and Mg) in soils and concentrations of HMs and (Ca + Mg) in plants, in the calculation of the buffering capacity of the surveyed soils for HMs.     

Theoretical and experimental substantiation of a thermogravimetric method for assessing the water-retention capacity and specific surface area of disperse systems

A conceptually new instrumental method has been proposed for the determination of the sorption fragment of the soil water retention curve and the specific surface area of soils and sediments by drying samples at different temperatures, which is based on fundamental models for relative air humidity and thermodynamic water potential (Ψ) as functions of temperature (T). The basic equation for the calculation of water potential in the first (linear) approximation is as follows: Ψ = Q–аТ, where Q is the specific heat of evaporation, and a is the physically substantiated parameter related to the initial relative air humidity in the laboratory. The setting of model parameters necessary for quantitative calculations has been performed from tabulated data for the saturated water vapor pressure as a function of temperature and results of an independent experiment with gradual air heating and synchronous automated control of air humidity and temperature with DS 1923 hydrochrons. The potentialities of the method have been demonstrated using literature data on the dehydration of soil colloids and our own results on the drying of a silty sandy soil (Arenosol) from Dubai, a light loamy soddy-podzolic soil (Albic Retisol) and a low-moor peat soil (Histosol) from Moscow oblast, and a loamy ordinary chernozem (Haplic Chernozem) from Krasnodar region.     

Mobility of heavy metals in polluted soils near zinc smelters

The distribution and the availability of Cd, Zn, Cu, and Pb along the entire profile of two highly polluted soils located near Zn smelters have been related to the chemical and mineralogical composition of the soil. Lead and Cu deposits always remain in the surface layers and their availability measured by neutral ammonium acetate extraction was very weak. The behavior of Cd and Zn appears different in sandy acidic podzolic soils and in neutral loamy soils. These metals are associated with the organic matter migration in podzolic soils, while they remain in the upper layers in loamy soils provided that the pH is higher than 6. When the pH drops below 6, the mobility of Cd increases while that of Zn increases only below pH 5. The availability of heavy metals is lower in neutral loamy soils than in sandy acidic soils due to precipitation of carbonates and phosphates. With increasing depth, Cd and Zn are more available if the soil is acid; but, if the soil is neutral and loamy the availability is kept low by adsorption on clays and free oxides. The results of the complex trace metals interactions with the soil components show a higher accumulation capacity for loamy soils than for sandy soils notwithstanding the fact that their CEC is similar.     

Contact angles at the water–air interface of hydrocarbon-contaminated soils and clay minerals

Contact angles at the water–air interface have been measured for triturated preparations of clays and soils in order to assess changes in their hydrophobic properties under the effect of oil hydrocarbons. Tasks have been to determine the dynamics of contact angle under soil wetting conditions and to reveal the effect of chemical removal of organic matter from soils on the hydrophilicity of preparations. The potentialities of static and dynamic drop tests for assessing the hydrophilic–hydrophobic properties of soils have been estimated. Clays (kaolinite, gumbrine, and argillite) have been investigated, as well as plow horizons of soils from the Republic of Tatarstan: heavy loamy leached chernozem, medium loamy dark gray forest soil, and light loamy soddy-calcareous soil. The soils have been contaminated with raw oil and kerosene at rates of 0.1–3 wt %. In the uncontaminated and contaminated chernozem, capillary water capacity has been maintained for 250 days. The contact angles have been found to depend on the degree of dispersion of powdered preparation, the main type of clay minerals in the soil, the presence and amount of oxidation-resistant soil organic matter, and the soil–water contact time. Characteristic parameters of mathematical models for drop behavior on triturated preparations have been calculated. Contamination with hydrocarbons has resulted in a reliable increase in the contact angles of soil preparations. The hydrophobization of soil surface in chernozem is more active than in soils poorer in organic matter. The complete restoration of the hydrophilic properties of soils after hydrocarbon contamination is due to the oxidation of easily oxidizable organic matter at the low content of humus, or to wetting during several months in the absence of the mazut fraction.     

Cadastral valuation of land contaminated with radionuclides

The methodology and procedure for cadastral valuation of land in the areas contaminated with radionuclides are presented. The efficiency of rehabilitation measures applied to decrease crop contamination to the levels satisfying sanitary-hygienic norms is discussed. The differentiation of cadastral value of radioactively contaminated agricultural lands for the particular farms and land plots is suggested. An example of cadastral valuation of agricultural land contaminated during the Chernobyl Nuclear Power Plant accident is given. It is shown that the use of sandy and loamy sandy soddy-podzolic soils with the ¹³⁷Cs contamination of 37–185 and >185 kBq/m² for crop growing is unfeasible. The growing of grain crops and potatoes on clay loamy soddy-podzolic soils with the ¹³⁷Cs contamination of 555–740 kBq/m² is unprofitable. The maximum cadastral value of radioactively contaminated lands is typical of leached chernozems.     

Influence of Rhizosphere Bacteria on the State of Heavy Metal Сompounds in the Soil–Plant System

Eurasian Soil Science - The results of a greenhouse experiment with the humus horizon of a sandy loamy soddy-podzolic soil are presented. It was contaminated with heavy metals added with sewage...     

Microbial use and decomposition of maize leaf straw incubated in packed soil columns at different depths

An experiment was carried out to investigate the decomposition and microbial use of maize leaf straw incubated in packed soil columns at different depths. The straw was incorporated into the top layer at 0–5 cm depth and into the bottom layer at 15–20 cm depth of a sandy or a loamy soil. Microbial biomass C was significantly increased after adding straw to the bottom layer of both soils. After adding straw to the top layer, this increase was significantly lower in the sandy soil and significantly higher in the loamy soil. Maize straw application significantly increased the ergosterol-to-microbial biomass C ratio in both soils from 0.26% to a mean content of 0.72% after adding straw to the top layer and to a mean content of 1.11% after adding straw to the bottom layer. The calculation of the maize-derived CO₂ production revealed that the mineralization rates of maize C were always higher in the sandy soil, with a mean of 20%, than in the loamy soil, with a mean of 14%. The application of maize straw always significantly increased the soil organic matter-derived CO₂ production. This increase was stronger in the loamy soil than in the sandy soil and stronger after application of the maize straw to the top layer than to the bottom layer. On average, 100% of the maize straw C was recovered in the different fractions analysed. In the layers with maize leaf straw application, 28% of the maize C was recovered as particulate organic matter (POM) > 2 mm and 32% as POM 0.4–2.0 mm, without a significant difference between the two soils and the depth of application. In the layers with maize leaf straw application, 19% of the maize C was recovered as microbial residue C and 3.1% as microbial biomass C. In the three layers without straw, the microbial biomass incorporated a further 2.4% of the maize C in the sandy soil, but only 0.9% in the loamy soil. Considerable amounts of substrate C were transferred within the microbial biomass over a decimetre distance. The finer pore space of the loamy soil seems to obstruct the transfer of maize-derived C. This was especially true if the maize leaf straw was added to the bottom layer.     

Structural and functional features of microbial communities in a soddy-podzolic soil under self-remediation conditions

The microbial component is one of the key factors responsible for soil fertility and soil quality. The sensitivities of some structural and functional parameters of soil microbial communities in soddy-podzolic soils under long-term self-remediation conditions were compared. The suitability of the parameters studied for quantifying the resilience of soil biota to agricultural intervention was studied.     

Agrocenosis Stability during Long-Term Application of Fertilizers on Soddy-Podzolic Soil

Eurasian Soil Science - In a long-term field experiment in the western part of the nonchernozemic zone of Russia (Smolensk oblast) on sandy loamy soddy-podzolic soil (Albic Glossic Retisol...     

Mechanisms of potassium uptake efficiency and dynamics in the rhizosphere of safflower and sunflower in different soils

Potassium uptake efficiency of safflower and sunflower was studied under semi-controlled conditions in loamy and sandy soils. Both species performed better in loamy soil. Safflower had higher agronomic efficiency and higher relative root length under suboptimal K supply. Safflower had higher specific root density and less root radius at all K levels. Safflower had higher relative root-shoot ratio under suboptimal K in loamy soil. Both species had similar K-influx at low and optimal K in loamy soil, while sunflower had higher influx under suboptimal and optimal supplies in sandy soil. Safflower had higher shoot demand in both soils under suboptimal and optimal K. Both species depleted similar amounts of soil solution-K under suboptimal K in sandy soil, while sunflower was more efficient under suboptimal levels in loamy soils. Sunflower depleted more extractable-K under both suboptimal and optimal K. Safflower could be considered K-uptake efficient crop.     

Distribution of transformed organic matter in structural units of loamy sandy soddy-podzolic soil

The effect of land use types and fertilizing systems on the structural and aggregate composition of loamy sandy soddy-podzolic soil and the quantitative parameters of soil organic matter has been studied. The contribution of soil aggregates 2–1 mm in size to the total C_org reserve in the humus horizon is higher than the contributions of other aggregates by 1.3–4.2 times. Reliable correlations have been revealed between the contents of total (C_org), labile (C_lab), and active (C₀) organic matter in the soil. The proportion of C₀ is 44–70% of C_lab extractable by neutral sodium pyrophosphate solution. The contributions of each of the 2–1, 0.5–0.25, and <0.25 mm fractions to the total C₀ reserve are 14–21%; the contributions of each of the other fractions are 4–12%. The chemically labile and biologically active components of humic substances reflect the quality changes of soil organic matter under agrogenic impacts. A conceptual scheme has been proposed for the subdivision of soil organic matter into the active, slow (intermediate), and passive pools. In the humus horizon of loamy sandy soddy-podzolic soil, the active, slow, and passive pools contain 6–11, 34–65, and 26–94% of the total C_org, respectively.