Haplic Chernozem Research Articles

Soil cover patterns in the forest-steppe and steppe zones of the East European Plain

Abstract The soil cover of the forest-steppe and steppe zones of the East European Plain is characterized by diverse soil combinations revealed during large-scale and detailed soil mapping against the background of a traditional zonal sequence of dominant automorphic soils alternating from the north to the south and clearly displayed on small-scale soil maps. The composition, configuration and functioning of particular soil cover patterns are determined by the soil forming factors acting within a given area. The elementary soil areas (detailed scale) and elementary soil cover patterns maps (large scale) of the Central Russian, Kalach, and Volga Uplands are created by both traditional and digital soil mapping methods. Low-contrasting soil combinations with the background Haplic Chernozems (Loamic or Clayic, Pachic) alternating with zooturbated Haplic Chernozems (Loamic or Clayic, Pachic) on convex elements of the microtopography and Luvic Chernozems (Loamic or Clayic, Pachic) on concave elements of the microtopography prevails under conditions of thick clay loamy parent materials and free drainage. Under conditions of shallow embedding by low-permeable clayey sediments, the soil cover includes Chernozems or Chernic Phaeozems with stagnic features in some part of the soil profile or even Mollic Stagnosols. The presence of shrink-swell clays of different ages leads to the formation of Bathyvertic Chernozems, Vertic Chernozems, Vertic Chernic Phaeozems and/or Pellic Vertisols. The presence of soluble salts in the parent material leads to the development of solonetzic soil complexes consisting of Protosodic or Sodic Chernozems and different types of Solonetzes.

Soil CO2 Emission, Microbial Biomass, and Basal Respiration of Chernozems under Different Land Uses

The relationships between the soil CO2 emission and microbial properties have been studied in Haplic Chernozem of steppe, forest (oak), bare fallow of the reserve area and in Urbic Technosols of Kursk city. The CO2 emission was monthly measured (May–October) from the soil surface (EMsurf) and two subsoil layers at the depths of 10 and 20 cm (EM10, EM20), and the soil temperature and water content were simultaneously recorded. Overall, 360 soil samples have been taken from the layers 0–10, 10–20, and 20–30 cm for determining the microbial properties (microbial biomass carbon, Cmic; basal respiration, BR). Soil chemical properties (the organic C content, total C, N, P, K, and Ca; and pH) have been measured in the samples taken in July. The EMsurf of steppe averaged 24 g СО2/(m2 day), which was 1.6, 1.5 and 6 times higher than that of forest, urban, and fallow soils, respectively. In the forest, EM10 and EM20 were two times higher than reference EMsurf; they were similar in the fallow and urban soils; and they were by 34% lower in the steppe soil. The soil CO2 emission of studied ecosystems depended weakly on soil temperature and water content during the growing season. The Cmic and BR (0–10 cm) of undisturbed ecosystems (steppe, forest) were higher by, on average, 3–5 and 2–4 times, respectively, than those of disturbed (fallow, urban) ecosystems. The positive correlations between EMsurf and Cmic, BR (0–10 cm) were found (r = 0.56 and 0.74, respectively). The seasonal average EMsurf for different land uses was controlled mainly (78%) by soil BR (linear regression). Therefore, the EMsurf from Chernozems of different land uses during the growing season might be predicted on the basis of BR measurements (0–10 cm).

Soil influences on uptake and transfer of pharmaceuticals from sewage sludge amended soils to spinach

Sewage sludge from wastewater treatment plants, which may contain various contaminants including pharmaceuticals, is often used as a soil amendment. These contaminants may subsequently be taken up by plants. In the present study we examined uptake of select pharmaceuticals from sewage sludge applied to soils by spinach plants. Seven soils were amended with sewage sludge from two wastewater treatment plants (A and B). Concentrations of compounds in plant tissues (roots and leaves) of spinach planted 45 days in these soils under greenhouse conditions were evaluated after harvest. The largest bioaccumulation in the roots and leaves was observed for sertraline (bioaccumulation factors (BAF) of 3.3–37.9 and 1–13.4, respectively), tramadol (1.3–10.0 and 4.8–30.0), and carbamazepine (2.2–17.2 and 6.1–48.8) and its metabolite carbamazepine 10,11-epoxide (not-quantified to 7.3 and 9.3–96.7). Elevated bioaccumulation in spinach roots was also identified for telmisartan (3.0–20.3) and miconazole (4.3–15.1), and leaves for metoprolol acid (not-quantified to 24.3). BAF values resulting from application of sludge B were similar to or moderately higher than BAFs from sludge A. The BAF values of carbamazepine and carbamazepine 10,11-epoxide in all tissues were negatively correlated with soil cation exchange capacity (CEC). This negative correlation between BAF and CEC was also observed for tramadol (A-roots and B-leaves), citalopram (B-roots), and telmisartan (B-roots) or between BAF and clay content for metoprolol acid (A-leaves and B-roots), tramadol (B-roots and A-leaves) and venlafaxine (B-roots). However, in the case of some other compounds (i.e. sertraline, amitriptyline, mirtazapine, metoprolol), uptake and the subsequent translocation and transformation from 3 soils of a higher pH and base cation saturation (Stagnic Chernozem Siltic, Haplic Chernozem and Greyic Phaeozem) significantly differed from 4 soils with a lower pH and base cation saturation (Haplic Luvisol, Haplic Cambisol, Dystric Cambisol and Arenosol Epieutric). Such observations proved strong compound dependent influences of soil conditions on various compounds bioaccumulations in plants and necessity of studying these processes always in diverse soils.

Ecotoxicity of Copper, Nickel, and Zinc Nanoparticles Assessment on the Basis of Biological Indicators of Chernozems

Ecotoxicity of nanoparticles (50–100 nm) of Cu, Ni, and Zn has been assessed by changes in biological indicators of an ordinary chernozem (Haplic Chernozem (Loamic)) of Rostov-on-Don in the laboratory model experiment with incubation of soil samples with nanopowders of these elements added to soil in concentrations 100, 1000, and 10 000 mg/kg. The effects of biological indicators have been determined 10, 30, and 90 days after soil contamination. The addition of Cu, Ni, and Zn nanoparticles led to a decrease of the total number of bacteria, abundance of Azotobacter bacteria, catalase and dehydrogenase activities, and germination and length of roots of radish sown. Reliable cases of hormesis were not detected. Nanoparticles of Cu and Zn showed higher toxicity than Ni nanoparticles, and this was inconsistent with the hypothesis, according to which the toxicity of nanoparticles depended only on their size and did not depend on chemical nature of the element. According to the integral indicator of biological state of soil, maximal toxicity of Cu, Ni, and Zn nanoparticles was observed on the 30th day after contamination.

Accumulation and transformation of benzo[a]pyrene in Haplic Chernozem under artificial contamination.

Polycyclic aromatic hydrocarbons (PAHs) have been a major concern because of their carcinogenicity, mutagenicity, teratogenicity and wide distribution in the environment. Over 90% of PAHs in the environment exist on soil surface/sediment. Benzo[a]pyrene (BaP) is one of the predominant PAHs in soil. Thus, it is critically important to understand the patterns of BaP accumulation and transformation peculiarities in soil for the risk assessment. The studies were conducted in model experiment with Haplic Chernozem spiked with various doses of BaP (20, 200, 400 and 800µgkg-1) equivalent to 1, 10, 20 and 40 levels of maximum permissible concentrations. The unique properties of Haplic Chernozem were studied allow to accumulate and transform BaP as well as barley plants ability to absorb of some BaP concentration. Extraction of BaP from the soil was carried out by the saponification method. The qualitative and quantitative determination of BaP and other polycyclic aromatic hydrocarbons (PAHs) was performed by high-performance liquid chromatography with fluorescence detection (Agilent 1260 Germany, 2014). BaP accumulation in soil depended on the applied BaP concentrations in Haplic Chernozem. Studying the features of PAHs transformation in the soil of a model experiment 1year after the compound application showed the BaP content in the soil decreased up to 11-40%. Two years after the BaP application the content in the soil decreased up to 15-44% from the initial BaP content in the soil. The percentage of BaP concentration reduction in Haplic Chernozem increased with an increase in the dose of the applied xenobiotic. An increase in the dose of the applied pollutant to the soil of the model experiment contributed to an increase in all PAHs, which indicated a rapid BaP transformation in Haplic Chernozem. The PAHs content in the soils of model experiment in the first year of the research formed the following descending series: pyrene > chrysene > fluoranthene > phenanthrene. In the second year of research the phenanthrene content became higher than the fluoranthene content. The content of these compounds exceeded 20% of the total PAHs content in the soil samples in the first and second years of the model experiment. The features of PAHs accumulation and transformation in soils under artificial pollution showed the degradation of large-nuclear PAHs, starting from 5-ring polyarenes, and their structural reorganization into the less-nuclear polyarenes, such as 4-, 3-, and 2-ring PAHs. During the 2years of the model experiment the BaP concentration in the soil decreased up to 15-44% from the initial BaP content in the soil.

Soil Moisture Measurement by the Dielectric Method

Measuring soil moisture by the dielectric method is considered. It was revealed that the complex dielectric permeability (CDP) affects the readings of sensors using different physical principles in different ways. The results of CDP measurements for six samples are given: river sand, bentonite, three samples of Haplic Chernozem (Loamic) of the Omsk region and a mixture of chernozemic material and river sand. Content of particles less than 0.01 mm in size in the samples varied from 1.7 to 72%; the content of organic carbon ranged from 0 to 4.12%. Measurements of CDP were performed at different values of moisture at the frequencies from 10 kHz to 4–8 GHz in the same cell using the original technique developed by authors. It was noted that at frequencies below 20–30 MHz, the dielectric permittivity is an ambiguous function of moisture owing to the strong influence of the conductivity of the soil solution and of interlayer dielectric relaxation on it. Moisture measurements are best to perform in the frequency range 0.5–3 GHz, where the effect of interlayer relaxation and soil solution conductivity on the CDP is negligible. Measurements of soil moisture and conductivity were performed using a Decagon 5TE capacitive sensor. The calibration dependency that is valid for different soils, considering the conductivity of the soil measured by this sensor was found. The error of moisture measurements using this dependency is 0.035 m3/m3. The use of individual calibration dependencies for each of soils reduces the error to 0.014 m3/m3. Results of the work can be used to improve the accuracy of soil moisture measurement by the dielectric method.

Introduction to the thematic set: Progress in Remediation of Polluted Soils

Lead Guest Editor: Jaume Bech Co-Guest Editors: Elena Korobova, M. Manuela Abreu, Carmen Perez-Sirvent, Hyo-Taek Chon and Nuria Roca The collection of papers presented in this Thematic Set is an outcome of the SSS8.4 Session ‘Progress in remediation for soils polluted by potentially toxic elements’, presented at the European Geosciences Union (EGU) Conference held in Vienna, April 2017. Soils are essential components of the environment, the basis of terrestrial ecosystems and a crossroad of biogeochemical cycles at the lithosphere-hydrosphere-biosphere-atmosphere interface. Soils are a limited and vulnerable resource and soil quality must be preserved. Anthropogenic mismanagement through poor industrial and mining practices, overuse of agrochemicals, bad disposal of sewage sludge and waste, cause contamination, environmental and health concerns. Therefore soil pollution needs innovative and eco-friendly technologies for its remediation. This Thematic Set contains 13 papers written by authors from 12 countries: Armenia, Italy, Japan, Jordan, Korea, Mexico, Mongolia, Philippines, Russian Federation, Spain, Thailand and USA. This collection of original studies focuses on five topics: 1) sequential extraction/speciation, 2) phytoremediation, 3) oxygen content in iron sulphides, 4) stabilization of Zn compounds in a long incubation experiment, and 5) bioavailability of potential toxic elements. ### Sequential extraction/speciation There are five papers dealing with this topic: Burachevskaya et al. studied the Zn fractional distribution in artificially contaminated Haplic Chernozem in South Russia, using the Miller and Tessier methods of sequential extraction. The authors concluded that the content of Zn in the fraction bound to the removed component obtained by the Tessier method area was lower than that obtained by the Miller method. Minkina et al. researched the Zn speciation in Technosols of the Karabash copper smelter, Southern Urals, Russia, using the combined fractionation scheme and a set of X-ray synchroton …

ASSOCIATIVE TO TRITICUM AESTIVUM L. BACTERIA AS A SOURCE OF STRAINS FOR BIOTECHNOLOGY OF THE RHIZOSPHERE

Associative microorganisms live in the zone of direct influence of plants namely in the soil, which is in close contact with the roots. They form complex communities on the roots of plants in terms of taxonomic composition and structural and functional o8rganization, which have polyfunctional effect on plants. Rhizosphere biotechnologies with the use of associative bacteria to a specific plant species allow increasing their productivity and quality, which contributes to the stability of agroecosystems. Therefore, the main goal of the current study was to isolate associative to Triticum aestivum L. bacteria from the southern chernozem (Haplic Chernozems), which was sampled in the steppe zone of the Crimea. The methodical approach was used to select associative microorganisms for a specific plant species. The number of microorganisms of the main ecological-trophic groups for three varieties T. aestivum were determined. The maximum number of rhizosphere microorganisms was identified for the Ermak variety, as well as the number of morphotypes isolated from the apical part of the root. As a result of the research, six strains of associative bacteria were obtained. They increased the seed quality of the studied varieties by 5% and the biomass of the seedlings by 80%. Identification by the 16S rRNA gene showed their belonging to different bacterial genera. Thus, the quantitative composition of the chernozem southern of the rhizosphere of three varieties of T. aestivum was determined. Five strains of associative bacteria promising for further biotechnology of the agrocenosis rhizosphere were isolated.

Dry sieving analysis of soil by vibratory sieve shaker: modification and optimization

This study performs a methodical experiment on adaptation and unification of soil dry sieving analysis. The analysis is based on the Savvinov dry sieving method that uses 0.5-1.5 kg air-dried soil samples which are passed through the 10, 7, 5, 3, 2, 1, 0.5, 0.25 mm sieves. The studied soils are silt loam Eutric Retisol and Haplic Chernozem. From each object, 50 kg of fresh soil was sampled from the plow layer (lm2area). Air-dried soil subsamples of 500 ± 0.5 g were used for analysis, clods bigger than 50 mm were gently crushed by pestle with rubber tip. The sieving parameters were the following: 50 Hz vibration frequency - 3000 rpm (depend on current), from 0.5 to 2.5 mm vibration amplitude and from 0.5 to 5 minutes sieving time. Sieve shaker mechanical work (J) was calculated for each mode. The data approximation was carried out by means of the asymptotic regression function. An optimal dry sieving mode was defined for each soil: Eutric Retisol - 1 mm vibration amplitude during 1 minute, Haplic Chernozem - 2.5 mm vibration amplitude during 2 minutes. In the case of sandy soils dry sieving doesn't require much effort. Therefore, in this experiment only fine macrostructure soils were selected (11-16 % < 2 um clay by laser diffraction method). As a result, the unified dry sieving mode of vibratory sieve shakers was developed which is applicable for all studied soils: 2.5 mm vibration amplitude during 2 minutes and 50 Hz frequency when 500 g air-dried soil sample is used.

Study of copper, lead, and zinc speciation in the Haplic Chernozem surrounding coal-fired power plant

The speciation of Cu, Pb, and Zn compounds in Haplic Chernozem under the anthropogenic impact of a power plant mainly operating on coal was studied. General tendencies in the distributions of Cu, Pb, and Zn among the compound forms were revealed using selective sequential extractions (Miller method modified by Berti and Jacobs (1996)), which is based on the nature of metals and the participation of soil components. In an uncontaminated soil occurring far from the emission source, 55–85% of total Cu, Zn, and Pb fractions are concentrated in the residual fraction characterizing the metal bond with silicates. In uncontaminated soils, the contents of Cu, Pb, and Zn in crystallized Fe compounds are largely higher than in its amorphous forms. Metals accumulate in the soil occurring near the power plant, which increases the total contents of Cu, Pb, and Zn in 1.3–2.5 times and their mobile (water-soluble, exchangeable, and carbonate-bound) compounds in 2–12 times. The largest contributions to the adsorption and retention of metals are made by silicates, as well as soil organic matter for Cu and Pb and nonsilicate Fe compounds for Zn. A significant increase in the exchangeable Zn fraction is observed in studied soils. The estimation of the degree of metal fixation in the soil was calculated Partition index of element, which reflects the degree of metal-soil bonding. It showed that the highest parameter value for the studied metals was found for the soils located at 15 km from the NPP, where the Index values approach 1; the lowest Index value is noted for contaminated soils nearby from the enterprise. Thus, sequential extraction is an effective tool to check the affinity of the soil components for Cu, Pb and Zn.

Relationships between the Organic Carbon Content and Structural State of Typical Chernozem

The influence of erosion degree and slope aspect on the structural composition of typical chernozems (Haplic Chernozems) and the qualitative characteristics of organic matter in these soils were studied. We determined the organic carbon content in separate structural units of the soils under different agroecological conditions of Kursk oblast. Aggregates of 3–1 mm in size played the decisive role in the structural state of typical chernozems; their total content and the content of carbon of organic compounds in them were higher than those for the aggregates of 10–3 and <1 mm in size. The contribution of organic matter and labile humic substances to the formation of water-stable soil aggregates was also considered. A tendency for an increase in the diameter of aggregates with an increase in their organic carbon content was displayed in the soils independently from the degree of their erosion. The content of carbon of labile humic substances in water-stable aggregates of the soils on north-facing slopes was higher than that in the soils on south-facing slopes. With an increase in the portion of labile humus participating in the formation of water-stable aggregates of typical chernozems, the diameter of these aggregates increased from 0.5–0.25 to 3–1 mm. This regularity was clearly displayed in the Ap and A horizons of typical chernozems on the interfluve and on the north-facing slope and in the Ap horizon of these soils on the south-facing slopes independently from the degree of soil erosion. The results of this study may be used in methodological recommendations on regulation of the aggregate and humus states of typical chernozems in agrolandscapes with sloping topography.

Water Retention Capacity of Soils in the Altai Region

Water retention curves (WRC) and some physical and chemical properties (particle-size composition, soil density, organic matter content, etc.) were determined for the major soil types of the Altai Region: southern chernozems of moderately dry steppe (Calcic Chernozems) and ordinary chernozems (Haplic Chernozems) of steppe with forest groves in local depressions, leached chernozems of the Altai foothills (Luvic Chernozems (Pachic)), and chestnut soils (Kastanozems) of dry steppe. These soils differ by texture. Overall, 420 soil samples were examined. The water retention curve was experimentally determined by centrifugation and capillarimetry, and approximated on the basis of the van Genuchten equation. The parameters of approximation were used for hydrological grouping of the soils by texture, which becomes heavier from the loamy sandy soils of dry steppe towards heavy loamy soils of the Altai foothills. The hydrophysical parameters are not differentiated along the soil profile and generally are in agreement with the humus accumulation process and the natural or anthropogenic soil compaction. An increase in parameter α reciprocal to the bubbling pressure is observed upon the transition from steppe Chernozems towards Kastanozems of dry steppe. The determination of this parameter is particularly important for modeling water and aeration conditions of irrigated soils and potential waterlogging. Quantitative descriptions of water retention curves with the use of approximation parameters made it possible to develop physically substantiated models for soil reclamation purposes.

Organic Matter of the Air-Dry and Water-Stable Macroaggregates (2–1 mm) of Haplic Chernozem in Contrasting Variants of Land Use

The content and the composition of soil structural units of different hierarchical levels were studied for Haplic Chernozems (Loamic, Pachic) of Kursk region under contrasting variants of land use (steppe and bare fallow). A detailed scheme of the method used to analyze the content and composition of organic matter in granulodensimetric fractions from the soil aggregates of different sizes and different water stability was developed. The major attention was paid to the study of aggregates isolated by the wet sieving method from the air-dry aggregates of 2–1 mm in size, as the most representative agronomically valuable aggregate fraction, Regardless of the land use, the content of the 2–1 mm air-dry aggretates was approximately the same in the soils under the steppe and the bare fallow. However, their water stability differed considerably between the steppe and the bare fallow. The long-term (52 yr) fallowing of the soil led to considerable losses of organic matter both in the whole soil and in different water-stable aggregates. Minimum losses were revealed for virtually all components of organic matter localized within undestroyed water-stable macroaggregates of 2–1 mm.

Possibilities of chemical fractionation and X-ray spectral analysis in estimating the speciation of Cu2+ with soil solid-phase components

Soil phases that are likely to scavenge ‘free’ metals include amorphous Mn and Fe oxides, organic matter, and clays. This paper reviews free forms of Cu and the methods in current use to quantify them. The information value of sequential extraction for assessing the speciation of Cu2+ in artificially contaminated Haplic Chernozem (up to 2000 Cu mg/kg) was shown in the selective removal of the main solid-phase components from the soil. It was revealed that carbonates, Fe (hydr)oxides, organic matter, and layered silicates affect the uptake of Cu by the soil. The speciation of Cu in the soil was studied by the Tessier sequential extraction method. To assess the selectivity of the extractants used and to estimate the role of different soil components in Сu partitioning, carbonates, Fe-Mn sesquioxides, and organic matter were removed from soil samples prior to the application of each sequential extraction scheme. No metal was revealed in the fraction bound to the removed soil component, which indicated the selectivity of the used extractants with respect to the soil components. It was found that, in the absence of a soil component, the role of other components in the retention of metal ions increases. When organic matter was removed from the soil, nonsilicate Fe compounds become the most active components in metal sorption, and the role of organic matter in metal retention increases in the absence of Fe oxides. Upon the removal of carbonates, the accumulation of metal in the exchangeable form increases significantly. Mechanisms controlling the fixation of metal by soil solid-phase components on the molecular level were determined using synchrotron radiation X-ray absorption near edge structure (XANES) spectroscopy. It was found that the surface structure and the composition of functional groups of the adsorbent have the leading importance in metal sorption. The combined use of chemical and physical analytical techniques fully characterizes the interaction of Cu with soil solid-phase components, which reduces its availability to adjacent environments and mitigates environmental risks.

МАГНІТНА СПРИЙНЯТЛИВІСТЬ ҐРУНТІВ У СКЛАДІ ЕРОЗІЄЗНАВЧИХ ДОСЛІДЖЕНЬ

Water erosion of the soil is a major factor in the degradation of agricultural land in Ukraine. About 13 million hectares of arable land need additional protection. The study of the influence of the mentioned hazard processes is important both for the scientists and land endusers. The purpose of the paper is to demonstrate the possibilities of soil magnetic susceptibility mapping in erosion studies. The comparison with traditional methods is implemented. The studies were carried out at the territory of Farm Enterprise "Phoenix" of the Bliznyukovsky district of the Kharkiv region at the distance of 6 km to the southeast of the Lozova. The study site is used for crop production. The relief of the site is complicated by the developed ravine network. The soil is ordinary chernozems (Haplic Chernozems in WRB classification). We have registered high correlation between magnetic susceptibility (MS) of the studied chernozems and humus content (organic matter). The Spearman correlation coefficient slightly depends on the frequency magnetic susceptibility coefficient. The results give the opportunity to recommend soil MS studies as the additional tool in soil erosion mapping. The magnetic measurements are expensive and fast for the humus (organic matter) identification of eroded soil. The relation of the values of soil MS and the value of potential soil loss at the studied area was low. The study of the magnetic mineralogy confirmed the absence of the anthropogenic soil pollution. We confirmed this by the values of the frequency dependence of magnetic susceptibility which were above 6. The domination of the superparamagnetic (SP) grains with the size less than 20 nm was confirmed by the values of the frequency dependence of magnetic too. The majority of the MS values are 10-20. The magnetic minerals of the studied soil have been formed in real time under the pedogenic (natural soil formation) process.

Soil physical and chemical properties changes after zinc contamination

The aim of this work was to study the effect of a high rate of Zn on the chemical bond forms of metal in soil and on the physical properties and organic matter of Haplic Chernozem under model experiment conditions. The metal sequential extraction procedure used in this study was the classical five-step method proposed by Tessier et al. (1979). The particle size distribution was determined by the pipette method (using the pyrophosphate procedure of soil preparation) (GOST 12536-79). The microaggregate distribution was determined in the same way as the particle size distribution analysis above, except that there was no chemical dispersant (sodium pyrophosphate) applied (only mechanical agitation with water) (GOST 12536-79; Vadyunina and Korchagina, 1973). The qualitative composition of organic matter was determined using the Tyurin procedure modified by Ponomareva and Plotnikova (Vorob’eva, 2006). Contamination of Haplic Chernozem with Zn acetates at high rates of 2000 mg/kg affected the physical and chemical properties of the soil. A significant increase in the first two soil fractions least strongly bound to the soil was observed in contaminated soils. Silicates and Fe-Mn oxides made the largest contribution to the Zn adsorption and retention. The content of organo-mineral particles in colloidal size increased, which resulted in an increase of the clay fraction content up to 4.5 % compared to the control. The qualitative composition of organic matter changed: the contents of free and sesquioxide-bound humic acids and free fulvic acids increased. Studies of soil physical properties and organic matter quality changes and chemical bond forms of Zn in soil are needed to better understand metal behaviors in the environment and implement repair strategies in different polluted soils.

Pedogenic Carbonates and Radiocarbon Isotopes of Organic Carbon at Depth in the Russian Chernozem

Conversion of native grasslands to agricultural sites has resulted in remarkable changes in soil carbon at depth, but its impact on soil diagnostic horizons is unknown. This study was conducted to radiocarbon date the soil organic carbon (SOC) and quantify pedogenic carbonates in the Russian Chernozem at depth at three sites: a native grassland field (not cultivated for at least 300 years), an adjacent 50-year continuous fallow field in the V.V. Alekhin Central-Chernozem Biosphere State Reserve in the Kursk region of Russia (UNESCO—MAB Biosphere Reserve), and a cropland in the Experimental Station of the Kursk Institute of Agronomy and Soil Erosion Control. All sampled soils were classified as Fine-silty, mixed, frigid Pachic Hapludolls (Haplic Chernozem). The radiocarbon age (14C date, y BP) of SOC was highly variable: in the native grassland field, it varied from post-bomb (A-horizon) to 8011 ± 54 y BP (C-horizon); in the continuous fallow, it varied from 1569 ± 41 y BP (Ap-horizon) to 11,380 ± 180 y BP (C1-horizon); and in the cropland, it varied from 1055 ± 38 y BP (Ap-horizon) to 11,805 ± 68 y BP (Ck-horizon). Cultivation resulted in morphological/diagnostic changes in the soil profile (conversion of A to Ap; conversion of Bw to Bk horizon) over a 50-year period. These changes are supported by radiocarbon dating of SOC and pedogenic carbonate distribution within the soil profile. The proportion of pedogenic carbonates was highly variable: in the native grassland, it was 27% (C-horizon); in the continuous fallow, it varied from 53% (Bk1-horizon) to 72% (C2-horizon); and in the cropland, it varied from 85% (A-horizon) to 10% (Ck-horizon). The radiocarbon age differences with depth among the soils reflect changes in the soil carbon dynamics resulting from cultivation.

Contemporary Trend in Erosion of Arable Ordinary Chernozems (Haplic Chernozems (Pachic)) within the Volga Upland (Saratov Oblast, Russia)

The current trend in erosion rate of ordinary chernozems in Saratov oblast has been assessed. Detailed studies have been performed in a small catchment area of the Bolshoi Kolyshley River (Medveditsa River basin) using the radiocesium and soil-morphological methods. Data of long-term hydrometeorological observations in the region, reported results of observations of water runoff and soil loss on the runoff plots of the South-Eastern Research Institute of Agriculture (Saratov oblast), results of analysis of the grain size and mineral composition of stratozems developed on the catchment valley bottom were also used for analysis. The quantification of sedimentation rate in the valley bottom during two time windows (1963–1986 and 1986–2017) based on the sediment dating using 137Cs as a chronomarker indicates their decrease at least in 4–6 times after 1986, which points to a proportional reduction in erosion rate on the plowed slopes of the catchment area. The analysis of the temporal variability of suspended yields in the regional rivers (Medveditsa and Khopyor) during the period from 1940 to the present time allows us to draw an analogous conclusion for the Volga Upland within Saratov oblast. The decrease in the erosion rate of ordinary chernozems could be mainly caused by the reduction in water runoff from slopes during the spring snowmelt because of reduction in soil freezing depth against the background of rising air temperature in winter and spring. This decrease in erosion rate during the snowmelt period was not balanced by the regional increase in rainfall erosion related to some increase in the rate of runoff-forming rainfalls. In the part of Saratov oblast, located within the Volga Upland, where the studied catchment is situated, on the contrary, even a reduction in the frequency of rains with a rainfall depth of more than 30 mm occurred over the last decades. The reduction in the cultivated land area since the late 1980s because of the abandonment of plowlands on the steepest slopes also contributed to the decrease in total soil loss by erosion at the river basin scale. Within the studied small catchment, the share of perennial grasses in crop rotations increased after 1986, which also led to reduction of the rate of erosion of ordinary chernozems.

Ecological Assessment of the Content of Cadmium in Soils and Crops in Southwestern Regions of the Central Chernozemic Zone, Russia

It is found that in Belgorod oblast during 2010–2014, cadmium mainly came into agrocenoses with organic fertilizers (0.4 g/ha, or 73.9%) and ameliorants (0.116 g/ha, or 21.4%). The lowest total content of cadmium in the A horizon (0.22 mg/kg) was noted in meadow-chernozemic soil (Greyzemic Stagnic Chernic Phaeozem (Clayic, Pachic)) developed on old alluvial calcareous deposits, and its highest content (0.42 mg/kg) was found in ordinary chernozem (Haplic Chernozem (Clayic, Pachic)), where loess-like clay is the main parent rock. Virgin leached chernozem (Luvic Сhernozem (Loamic, Pachic)) formed on loess-like loam, contained 0.33 mg Cd/kg in the A horizon, which almost coincided with the mean content of this element (0.32 mg/kg) in the plow layer of leached chernozems on reference plots. No exceeding of the tentative permissible concentration of cadmium was revealed in arable soils. In crops, the content of cadmium was highest in sunflower seeds (0.086 mg/kg) and soya beans (0.072 mg/kg), and lowest in peas (0.032 mg/kg) and white lupine beans (0.013 mg/kg). The biological adsorption factor varied within the range from 0.97 (while lupine beans) to 10.8 (sunflower seeds) for target agricultural crops and from 0.41 (while lupine straw) to 4.63 (soya straw) for side products.

The Soil Structure Changes under Varying Compost Dosage

Abstract The influence of different application of grape marc compost on the soil structure and the water stability of soil aggregate were studied in the course of four-year experiment. The trial was carried out in a Velké Bílovice vineyard in the Czech Republic. The altitude of the locality is about 200 m above sea level, the long-term average annual precipitation is 550 mm, the long-term average annual temperature is 9.5°C. The soil is Haplic Chernozem, loamy textured. Three variants were established: Variant 1 - control, no compost, Variant 2-30 t of compost per ha, Variant 3-60 t of compost per ha. The compost from pomace, poultry droppings, mown grass and straw was made in an EWA aerobic fermentor in an intensive and controlled process in an enclosed space and shallow ploughed (0-0.15 m) into the soil every year after harvest. The results of the experiment were statistically processed by multifactorial analysis of variance and then by Tukey’s test of simple contrasts. The highest values of structural coefficient and water stability of soil aggregate were found in the variant with the highest dosage of compost. It was found that the application of grape pomace compost to the soil had a positive effect both on the soil structure and the water stability of soil aggregates.