The effect of pollution with oil and oil products on the biological status of ordinary chernozems

The effect of pollution of an ordinary chernozem with oil and oil products depends on the nature and concentration of the pollutants, their distribution in the soil profile, and the period of the pollution. The soil contamination causes a rise in the number of microorganisms and changes in their species composition: a decrease in the diversity of micromycetes and an increase in the diversity of bacteria. In most cases, it inhibits the activity of soil enzymes. Oxidoreductases are more sensitive to oil pollution than hydrolases. The soil ecological functions are disturbed under the impact of contamination.     

The impact of antibiotics (benzylpenicillin,and nystatin) on the biological properties of ordinary chernozems

In recent years, the input of antibiotics into soils has sharply increased. We studied the impact antibiotics (benzylpenicillin, pharmasin, and nystatin) at different concentrations (100 and 600 mg/kg) on population densities of microorganisms and enzymatic activity of ordinary chernozems in model experiments. The applied doses of antibiotics had definite suppressing effects on population densities of microorganisms (up to 30–70% of the control) and on the soil enzymatic activity (20–70% of the control). Correlation analysis showed close correlation between the concentrations of antibiotics and the population densities of soil microorganisms (r = ?0.68–0.86). Amylolytic bacteria had the highest resistance to the antibiotics, whereas ammonifying bacteria had the lowest resistance. Among the studied enzymes belonging to oxidoreductases and hydrolases, catalase and phosphatase had the highest and the lowest resistance to the antibiotics, respectively. The effect of antibiotics on the biological properties of the chernozem lasted for a long time. The studied parameters were not completely recovered in 120 days.     

Physical properties of ordinary chernozems in steppe landscapes adjacent to forests

The spatial changes in the ecological conditions of the humus formation; the humus content and reserves and its fractional-group composition and amphiphilic properties; and the structure, density, and water absorption coefficient of ordinary chernozems were studied on nine key plots at distances of 34 and 2 km from two forest massifs of different sizes??the Buzuluk Bor (111 000 ha) and a small birch grove (25 ha)??in the steppe zone of the Cis-Ural region. With an increase in the distance from the forests, the soil humus reserves decrease, the C_ha/C_fa ratio becomes larger, and the portion of hydrophilic and amphiphilicneutral fractions in the soil organic matter increases. In the same direction, the structure coefficient decreases (from 2.5?C3.7 to 1.5?C2.2), the soil density gradually increases, and the water permeability decreases and remains within the optimal values range.     

Changes in the main physical properties of ordinary chernozems under the impact of irrigation

The character of the quantitative changes in the main physical properties of ordinary chernozems under the impact of irrigation has been studied. It is shown that irrigation leads to a weak or moderate degradation of the aggregate state of the soils and a weak degradation of the soil bulk density, total porosity, and air capacity.     

Changes in the ecological and biological properties of ordinary chernozems polluted by heavy metals of the second hazard class (Mo,Co, Cr,and Ni)

The pollution of ordinary chernozems by heavy metals of the second hazard class (Mo, Co, Cr, and Ni) results in a decrease in the numbers of saprotrophic bacteria and fungi and bacteria of the Azotobacter genus; the catalase and invertase activities and the rates of the cellulose and urea decomposition also decrease. The soil phytotoxicity becomes higher. With respect to their ecological hazard, the studied heavy metals may be arranged into the following sequence: Cr > Co ≥ Ni > Mo.     

The influence of microrelief on the agrochemical properties of chernozems and the yield of spring wheat and barley

The influence of microrelief on the fertility of ordinary chernozems and the yield of cereal crops was studied in the Krasnoyarsk forest-steppe. The microrelief was shown to affect the humus state and the agrochemical properties of the chernozem. The productivity of the cereals was shown to differ by 1.3–2.6 times in the areas where the microrelief was strongly pronounced, and the yield of the cereal crops grown in depressions was lower by 1.1–1.8 times as compared to that on the flat areas. The correlation between the plant productivity and the humus content and the pH_salt in the soil was revealed. In order to take into account the influence of the microrelief and to reduce its effects on the yield of crops, the scale of soil and agrochemical investigations is recommended to be increased. Within the boundaries of the existing agricultural lands, the geochemical zones of removal, transport, and accumulation of soil material should be determined.     

The influence of relief on the humus content in chernozems

Data on the influence of relief on the humus formation in chemozems are given. The insolation coefficient is proposed for the assessment of the solar energy distribution over the ground surface depending on the slope gradient and aspect. Specific features of the humus accumulation in soils on parent rocks different in texture are estimated using the proposed calculated coefficients.     

Heavy metals in ordinary chernozems on slopes of different gradients and aspects

The impact of slope aspect and gradient on the contents and distribution of heavy metals (Mn, Cu, Zn, Co, Ni, Pb, and Cd) in the profiles of ordinary chernozem (Haplic Chernozems) was studied in Kursk oblast. Slope aspect was found to be a significant factor controlling the distribution of most of the bulk, mobile, and acid-soluble compounds of heavy metals, whereas the position on the slope (slope gradient) did not exert a significant influence on the distribution of elements. Bulk compounds of Co, Ni, Pb, and Cd showed the eluvial type of distribution in the soil profiles along with accumulation in the lower horizons. Distribution patterns of the mobile Cu, Co, Ni, Pb, and Cd were similar to those of the bulk ones. The latter phenomenon may be attributed to the high content of carbonates, an increased content of clay, and some alkalization of the soil solution in the lower horizons.     

Mercury and arsenic pollution in soil and biological samples around the mining town of Obuasi,Ghana

Young seedlings raised from six different Norway spruce seed provenances were grown in heavy-metal contaminated soils at two severely polluted areas. After ten months, the rate of survival ranged from 30% – 42% and from 45% – 52% at the two polluted areas, respectively. Comparisons of the genetic structure analysed at eight polymorphic enzyme loci showed that the heterozygote frequencies at four of these loci have substantially increased in the surviving seedling collections across all provenances as compared to the initial embryo samples. These results were discussed in relation to the metabolic role of the respective enzymes in response to environmental stress and the possibly greater reaction efficiency of the heterozygous enzyme phenotypes in order to recognize a probable overdominant selection regime.     

Biological mineralization of organic matter in the modern virgin and plowed chernozems,buried chernozems,and fossil chernozems

The phenomenon of mineralization (biological mineralization) of organic matter in chernozems has been studied. A decrease in the content of C_org with time can be considered an index of the organic matter mineralization. It is suggested that the humus horizons of modern chernozems contain the pools of organic matter of different ages: easily decomposable organic matter, labile biologically active humus, stable biologically active humus, and relatively inert humus. The composition and mean residence times of these pools and their contribution to the total organic matter content have been estimated. The particular types of the biological mineralization have been determined on the basis of the comparison between the velocities of mineralization (M) and humification (H) processes: total unidirectional mineralization (M ≫ H), equilibrium mineralization (M ∼ H), nonequilibrium mineralization (M> <H), and zero mineralization. The separation of subtypes is based on data on the relative rates (%) of the organic matter mineralization. On the basis of available experimental data on chernozems buried under kurgans and in loess sediments (with the age of up to 800 ka), the quantitative relationship of the humus content in the buried soils on their age has been found; it has an exponential shape. During the first 100 ka after the soil burial, the soil humus content gradually (with a slowing intensity) decreases from 100–75 to 6.5% of its content in the virgin chernozems. Then, 100–1000 ka after the soil burial, the soil humus content remains approximately constant (6.5% of the initial level, or 0.3% of the soil mass). The rates of mineralization have been estimated. It is shown that the elemental composition (C, H, N, O) of humic acids remains relatively stable for a long time due to the regeneration of the chemical structure of humus (matric restoration of humus). It is suggested that several different forms of humus related to pedogenesis should be distinguished in the biosphere. The renewable humus in the equilibrium state with the environment is typical of the open biospheric (soil) systems. The fossil humus, whose content decreases with time, and whose composition remains stable, is typical of the semiclosed and closed systems. With time, it transforms into residual humus, whose content and composition remain stable. The fossilized organic matter in the fossil soils and sediments of the past geological epochs (Mesozoic and Paleozoic) considerably differs from the renewable, fossil, and residual humus.     

Physical properties of chernozems on slopes in the landscape farming system

Changes in the physical status of soils on the slopes in the landscape farming system were studied. It was found that agricultural use affected the main physical properties of the soils: the bulk density and the water stability of the aggregates. The soil is more compacted on a slope with a gradient of 1–3 degrees, and a decreased water stability of the aggregates is observed on a slope with a gradient of 3–5 degrees.     

Changes in the biological properties of an ordinary chernozem exposed to gamma radiation

The dynamics of changes in the number of microorganisms and biochemical properties of an ordinary chernozem were studied in model experiments 3, 30, and 90 days after the soil was subjected to gamma radiation at doses of 0.12–2.0 Mrad. The microscopic fungi are the most radiosensitive soil microorganisms. In 90 days of incubation after the gamma radiation, the number of microorganisms remained lower than that in the control variant by 31–96% in accordance with the dose. The enzyme activity of the ordinary chernozem, as compared to that of the microorganisms, was more resistant to the gamma radiation. The integral index of the soil biological state (ISBSI) decreased by 20–63% upon the radiation depending on the dose applied. After 90 days, the ISBSI value was close to the control variant (doses of 0.1–0.5 Mrad), whereas, in the variants with high doses of radiation (1.0 and 2.0 Mrad), its values were 46 and 59% lower, respectively, than in the control. The rate of restoring of the biological properties was related to the dose of radiation: the less the dose, the quicker the rate of restoration of the biological properties of the ordinary chernozem. However, at the high levels of gamma radiation, some biological properties were not restored even after 90 days.     

Assessment of biological activity in agrogenic and natural chernozems of Kabardino-Balkaria

Parameters of biological activity (humus and microbial biomass reserves, potential intensity of the CO₂ emission, and enzyme activity) have been determined in arable and natural chernozems on the plains of Kabardino-Balkaria as a part of the system for the ecological assessment of the state of the soil cover. Integral parameters of the eco-biological state of studied soils have been calculated on the basis of obtained data, and the level of changes in their total biological activity has been determined. A statistically significant decrease of the values of all the considered biological properties under the impact of tillage has been found. The data of two-way ANOVA suggest a stronger influence of agricultural management in comparison with genetic features of chernozems at the level of subtype. Differential approach is insufficient for evaluating the total level of soil biological activity, because there are many biological properties of soil, and the degrees of their changes in agrogenic soils are different. An integral approach has been used; it integrates the obtained data into a single integral assessment parameter. In arable soils, this integral parameter decreases by 39–46% and makes it possible to assess the degree of disturbance of the ecological functions of soils and their capacity for self-restoration.     

Potassium status and clay mineralogy in ordinary chernozems treated with different rates of potassium fertilizers

The effect of a single instance of potassium fertilization at rates of 0, 70, 140, and 280 kg/ha on the potassium status and clay mineralogy was studied in a field experiment on ordinary chernozems. The content of exchangeable potassium determined by the Maslova method and the potassium potential vary with greatest reliability in response to increasing fertilizer rates. The content of easily exchangeable potassium and the potassium-buffering capacity are insignificantly affected by the application rate of potassium fertilizers. The chernozems under study without fertilization are characterized by a low supply of available potassium. When potassium fertilizers are applied at rates of 70 and 140 kg/ha, the soils pass into the category of unstable or high supply according to different gradation systems. The lower limit of the high or optimal supply category is reached only at the application of 280 kg/ha of potassium fertilizer. However, even in this case, chernozems are characterized by a low potassium supply according to the value of potassium potential and the content of nonexchangeable potassium. A single application of potassium fertilizers does not cause significant changes in the contents of illites in the clay fraction.     

The influence of climate cycles on the water regime and carbonate profile in chernozems of Central European Russia and adjacent territories

The influence of long-term “dry” and “wet” climatic cycles on the water regime, hydrological parameters, and carbonate profiles of chernozems in Central European Russia and adjacent territories was studied. The hydrological and carbonate profiles were found to change during the wet cycle. However, the upper part of the hydrological profile is basically unchanging, whereas in its lower part, the number of hydrological horizons and contrast in their moistening decrease in the forest-steppe chernozems and increase in the steppe chernozems. The frequency of through wetting of chernozems increases during the wet cycles. The vertical lithological heterogeneity of the parent material affects the soil moisture status. In the wet climatic cycle, the moisture content above the lithological contact increases resulting in the development of the features of soil hydromorphism. In the carbonate profile, the character of pedofeatures is changing: some carbonate neoformations disappear, while the other ones develop. Possible variations of the periodically percolative water regime were revealed in chernozems. The classification of water regime proposed by A.A. Rode may be updated based on the data obtained during the dry climatic cycle. Rode’s hypothesis about cyclic variations in the soil water regime is confirmed.     

The effect of long-term irrigation on the properties of leached chernozems in the forest-steppe of the southern Cis-Ural region

The effect of long-term irrigation (more than 30 years) on the properties of leached chernozem under vegetable crops has been studied. It is shown that the agrophysical, chemical, and physicochemical properties of the soil have worsened. The accumulation of salts is revealed.     

The development of chernozems on the Dniester-Prut interfluve in the Holocene

The development of forest-steppe and steppe chernozems on the Dniester-Prut interfluve in the Holocene was studied on the basis of data on the paleosols buried under archaeological monuments of different ages. The parameters of the mathematic models of the development of the soil humus horizons in different subtypes of chernozems were calculated. They were used to determine the rate of this process and the age of the soils formed on the surface of Trajan’s lower rampart. The climate-controlled changes in the character of the soil’s development in the Late Holocene were differently pronounced in the different subtypes of chernozems. The suggested differentiation of the trends in the development of the humus horizon in the studied chernozems corresponds to the differences in the soil-forming potential of particular areas (as judged from the energy consumption for pedogenesis).     

Biological activity of the humus horizon of ordinary chernozems as an indicator of the ecological state of agroecosystems in Bashkortostan

A comparative analysis of the biological activity has been performed in the soils of Transural Bashkiria developing under natural perennial grasses and under sown herbs. It is shown that the structure of the microbial community in the soils under natural perennial grasses (fescue, brome grass, and couch grass) prevents the removal of nitrogen from the ecosystem and favors nitrogen fixation in the microbial pool of the trophic chain. The method of multisubstrate testing points to certain differences between the metabolic potentials of the microbial communities of the soils under natural grasses and sown herbs. The high values of the integral index of health of the microbial system in the soils under natural perennial grasses attests to their efficiency in sustaining the soil fertility.