Ecological-hydrological and genetic features of chernozem-like soils of closed depressions in the northern Tambov Lowland

Specific features of the genesis and water regime of soils in closed depressions were studied in two catenas located on the interfluvial and terrace surfaces. In humid years and in the years with moderate precipitation, the surface flooding up to early May reduced the Eh values up to 60–100 mV in the soils of the interfluvial depressions. The contrasting stagnant-percolate water regime under the surface waterlogging caused podzolization of the soils manifested in the skeletans, iron nodules, humus cutans, and podzolic horizons. The pro-files acquired eluvial-illuvial differentiation, and the water-physical properties of the soils became less favorable. In the soils of the terrace depressions upon bogging due to the shallow ground water and stagnation of water up to mid-July, the Eh values decreased to ?20 to ?80 mV. The reductive conditions were responsible for the appearance of the morphochromatic signs of gley. The ground water of bicarbonate-calcium composition at a depth of 80–120 cm hindered podzolization. The soils with features of gley and podzolization are low-productive.     

Methods for quantitative diagnostics of degree of hydromorphism of chernozem-like soils (based on example of soils of northern Tambov Plain)

The hydrologic features of chernozem-like soils of the northern Tambov Plain reflect the crystallinity of nonsilicate iron contained in ferromagnetic concretions, as well as the qualitative humus content and other properties. The possibility of using Schwertmann’s criterion and swampiness coefficient in the Zaidel’man-Ogleznev method as diagnostic indices of degree of hydromorphism is shown. A new diagnostic index is suggested, i.e., the hydromorphism criterion (K_I–II); the relation of the optical density of the extraction of alkaline and alkaline pyrophosphate from fine-earth arable land horizon is based on its definition.     

Chemical properties of soils in closed depressions of the northern Tambov Plain

Chemical properties of chernozem-like soils in closed depressions on different relief elements in the northern part of the Tambov Plain differ significantly. The soils with podzolic features in depressions on the watershed have a high acidity and a low degree of base saturation. The soils on the above-floodplain terrace are neutral and saturated with bases. When the degree of moistening increases, the share of magnesium in the total exchangeable bases increases to 30–35%. In the soils of surface flooding under gleyzation conditions, iron is leached from the fine earth, and iron nodules are formed. In the soils formed under the impact of groundwater, iron diffusion is observed in the surface layers. In the podzolic horizons of soils on the watershed, humus acquires a fulvic-humic character. In the soils formed under the impact of groundwater and water stagnation conditions typical for gleyed soils, the Cha: Cfa ratio is higher than 1.     

Mobile forms of phosphorus and iron compounds in chernozem-like soils in the northern part of the Tambov plain

Moisture content and redox conditions are factors determining the dynamics of the content of mobile phosphorus in chernozem-like soils moistened and waterlogged by groundwater and surface water. When the moisture content increases and oxidizing conditions are still present in soils belonging to the chernozem type that contain a high concentration of calcium phosphates, the latter transform from apatite into more mobile forms, Ca-PI and Ca-PII. In chernozem-like soils with a high concentration of iron phosphates under reducing conditions, the amount of phosphorus extracted with 0.1 N H₂SO₄ increases owing to the transition of iron phosphates into a mobile state. Precipitations enriching the soil with atmospheric oxygen promote the increase in the value of the oxidation-reduction potential (Eh), thereby decreasing the mobility of iron phosphates.     

Concretions in typical chernozem,gleyed chernozem-like,and solonetzic chernozem-like soils of the southern Tambov Lowland

A system for the diagnostics of chernozemic soils of the Tambov Lowland based on concretions is proposed for agricultural and reclamation purposes. The relationships between the structure and composition of the carbonate concretions, the long-term water regime of the soils, and the productivity of the crops have been established. The dense concretions in the typical chernozem testify to the depth of the seasonal wetting; the angular-rounded concretions in the deeply gleyed chernozem-like soil, to the upper boundary of the capillary fringe; and the angular concretions with sharp edges and cavities in the gleyic chernozem-like soils, to the groundwater table. In the chernozem-like soils that were waterlogged with bicarbonate-sodium water, the black angular concretions were formed in the solonetzic horizons, while the weakly compacted light-colored ones, in the zone of the capillary fringe. Humic acids were responsible for the color of the dark neoformations, and fulvic acids predominated in the light-colored ones. The appearance of black fine nodules indicated periodic surface water stagnation. Manganese predominantly accumulates in these nodules. The structure of the Mn-Fe concretions in the plow horizon observed at a magnification of 40–50 times has a diagnostic importance. The short-term (2–3 weeks) water stagnation leads to the formation of fine-stratified concretions, and the long-term (up to 1.5 months) stagnation promotes the formation of uniform porous ones. The solonetzic process induced by the bicarbonate-sodium water results in the appearance of mottled concretions.     

Manganese, iron, and phosphorus in nodules of chernozem-like soils on the northern Tambov Plain and their importance for the diagnostics of gley intensity

Nodules (nodules) forming in the chernozem-like soils of flat-bottomed closed depressions on the northern part of the Tambov Plain differ in their morphology and chemical composition as related to the degree of hydromorphism of these soils. The highest are the coefficients of Mn, P, and Fe accumulation in the nodules from these soils. The Fe to Mn ratio grows with the increasing degree of hydromorphism. Under surface moistening, the maximal amounts of mobile Mn and Fe compounds were extracted from the nodules of the most hydromorphic podzolic chernozem-like soils; under the ground moistening, their greatest amounts were extracted from the least hydromorphic soil—the weakly gley soil. In the first case, the content of organic phosphates in concretions amounted to 30–50%; in the second one, 2–3% of their total content. Under surface moistening, the proportion of active mineral phosphates becomes higher with the increasing hydromorphism: from 30 (podzolized soil) to 70% (gleyic podzolic soil). Under ground moistening, on the contrary, their proportion decreases from 70–89% in the weakly gley soil to 40–50% in the gley chernozem-like soil. The possibility to determine the degree of hydromorphism of chernozem-like soils based on the coefficients of bogging is shown. The expediency of using Schvertmann’s criterion in these studies is assessed.     

Ecological-hydrological and genetic features of the soils of the Tambov Plain

Specific features of the genesis of chernozem-like, solonetzic chernozem-like soils, and hydromorphic chernozem-like solonetzes were investigated on the southern Tambov Plain. Typical chernozems occupy well drained areas. The yield of cereals is limited by the amount of precipitation. On the flat surface of weakly drained watersheds, deeply gleyed chernozem-like soils are formed under the influence of bicarbonate-calcium ground water and water stagnation on the plow sole. In closed depressions with the 1.5- to 2.0-month long stagnation of surface water on the compact lower horizons, podzolized gleyic chernozem-like soils are formed. They have favorable physical properties, weak eluvial differentiation, and rather high acidity. In humid and moderately humid years, the cereals on these soils are waterlogged; in dry years, their yield increases by 20% as compared to that on the typical chernozem. In the low undrained areas of the watersheds, solonetzic chernozem-like soils and hydromorphic chernozem-like solonetzes are formed under the influence of bicarbonate-sodium water. Despite the unfavorable physical properties of the solonetzic horizons, their better supply with moisture determines the possibility to obtain stable high yields of cereals on the solonetzic chernozem-like soils. The productivity of the gleyic chernozem-like solonetzes is low irrespective of the humidity of the year.     

Characteristics of bacterial communities in hydromorphic soils of northern regions

An analysis of the abundance and taxonomical structure of the heterotrophic block of aerobic and conditionally anaerobic bacteria in hydromorphic tundra and taiga soils was carried out. The decline of the cultivating temperature from 20° to 5° did not result in the reduction of bacterial abundance. The spectrum of the bacterial dominants in the northern cryogenic soils is wider under 4–6°, which is indicative of the lowtemperature adaptation of bacteria. Oligotrophs and copiotrophs predominate the bacterial communities of the explored soils. However, among hydrolytic bacteria, active chitin destructors, represented by Bacillus and Janthinobacterium, were found.     

Clay minerals in chernozem-like soils of mesodepressions in the northern forest-steppe of European Russia

In the northern forest-steppe of European Russia, under the conditions of surface waterlogging (freshwater) and a stagnant-percolative regime, gleyic podzolic chernozem-like soils with thick light-colored eluvial horizons are formed. These horizons are close or similar to the podzolic horizons of bog-podzolic soils in many properties of their solid phase. They are bleached in color and characterized by the removal of Ca, Mg, Fe, Al, and Mn and the relative accumulation of quartz SiO₂. These soils differ from leached chernozems in their acid reaction and very low CEC, the presence of Fe-Mn concretions and coatings, and the significant decrease in the clay content in the A2 horizon as compared to the parent rock. The soils studied differ significantly from loamy podzolic and bog-podzolic soils by the composition of the clay minerals in the A2 horizons: (1) no essential loss of smectite minerals from this horizon was found as compared to the rest of the solum, (2) pedogenic chlorites (HIV and HIS) are absent, and (3) the distinct accumulation of illites is observed as compared to the subsoil and parent material, probably, due to the process of illitization.     

Genesis and properties of dark-colored chernozem-like soils of mesodepressions under fallow in the northern Caspian region

Specific features of the most fertile soils in the semidesert zone of the northern Caspian region—dark-colored chernozem-like soils of large mesodepressions—are analyzed. The recent regional rise in the groundwater level and the restoration of steppe vegetation in the fallowed soils of large mesodepressions, especially near forest strips and forest plantations, have led to certain changes in the microfabric and chemical composition of these soils, as well as in the soil organic matter properties.     

Fractional composition of humus in leached chernozems and gleyed podzolized chernozem-like soils of the northern forest-steppe zone

The composition of humus in leached chernozems differs from that in gleyed podzolized chernozem-like soils in the northern forest-steppe zone of European Russia. Leached chernozems have the fulvate-humate humus. Gleyed podzolized chernozem-like soils have the humate-fulvate humus. A more aggressive composition of humus in the latter soils is caused by their overwetting and the development of gley processes under conditions of a stagnant-percolative soil water regime.     

Iron in hydromorphic gray forest soils

The amorphous iron content in the upper soil horizons, the profile distribution of iron oxides and hydroxides, and the Schwertmann (Fe_o/Fe_d) ratio can be used as diagnostic criteria for the degree of gleyization in the classification of hydromorphic soils. Drainage removes chemical elements, e.g., nonsilicate Fe, from soils.     

Dark gray soils on two-layered deposits in the north of Tambov Plain: Agroecology, properties, and diagnostics

Dark gray soils in the Tambov Plain are developed from the light-textured glaciofluvial deposits underlain by the calcareous loam. Their morphology, water regime, and productivity are determined by the depth of the slightly permeable calcareous loamy layer, relief, and the degree of gleyzation. The light texture of the upper layer is responsible for its weak structure, high density, the low content of productive moisture, and the low water-holding capacity. If the calcareous loam is at a depth of 100?C130 cm, dark gray soils are formed; if it lies at a depth of 40?C70 cm, temporary perched water appears in the profile, and dark gray contact-gleyed soils are formed. Their characteristic pedofeatures are skeletans in the upper layers, calcareous nodules in the loamy clay layer, and iron nodules in the podzolized humus and podzolic horizons. The appearance of Fe-Mn concretions is related to gleyzation. The high yield of winter cereals is shown to be produced on the dark gray soils; the yields of spring crops are less stable. Spring cereals should not be grown on the contact-gleyed dark gray soils.     

Mountainous meadow chernozem-like soils of high mountains in the North Caucasus region

Original and literature data on the soil-forming conditions and the morphology, physicochemical properties, and bulk chemical and mineralogical composition of mountainous meadow chernozem-like soils of the North Caucasus region indicate that these soils are developed from the coarse-textured pebbly colluvium of calcareous bedrock under the impact of humus accumulation and clay formation. The intensity of these processes is directly related to the activity of soil biota. Suggestions aimed at improving the classification of high-mountain soils are discussed.     

Specific features of the development of soils of hydromorphic ecosystems in the northern taiga of Western Siberia under conditions of cryogenesis

Differently directed and heterochronous cryogenic processes have contributed to the contrasting soil cover patterns and spatial heterogeneity of the properties of soils in hydromorphic ecosystems of the discontinuous permafrost zone of the northern taiga in Western Siberia. Frost heave and permafrost thawing within ecosystems of highmoor bogs have led to the development of specific cryogenic landforms, such as flat-topped and large peat mounds. A set of cryogenic soils is developed in these ecosystems; it includes different variants of cryozems, gleyzems (Cryosols), and peat soils (Histosols). The distribution of these soil types is controlled by the local topography and thawing depth, other factors being insignificant. Alternation of peat horizons of different types and ages, whirl-like patterns of horizon boundaries, considerable variations in the thickness of soil horizons, and inversions of soil horizons under the impact of frost cracking, frost heave, and cryoturbation are typical of the considered soils. Thawing depth is the most significant factor affecting the thickness of organic horizons, the soil pH, and the degree of decomposition of peat. As a result of the upward movement of bog ecosystems under the impact of frost heave, peat soils are subjected to considerable transformation: peat horizons undergo mineralization, and the thickness of organic horizons decreases; in some cases, eluvial–illuvial differentiation of the mineral horizons takes place, and peat podzols are developed. However, the opposite process of the return of the soils to the bog stage of pedogenesis with peat accumulation may take place in any time in the case of activation of thermokarst processes.     

Difference in the pH values of hydromorphic soils in field and laboratory analyses

There are marked differences in the pH values determined in water suspension under laboratory conditions and in soil solution under field conditions in hydromorphic soils (gleysols and stagnosols). The value δpH = pH_susp–pH_sol can be either positive or negative. Among the main factors that affect the value of δpH are the laboratory preparation of soil samples and the suspension effect. The sign of the pH effect (value of δpH) depends on the participation of humus, carbonate, and exchange bases in the formation of aggregates destructed in the laboratory. The value of δpH is negative in noncalcareous soils with low content of exchangeable bases and fulvate composition of humus and positive in calcareous soils or soils enriched with exchangeable bases and humate composition of humus. In cases of a significant δpH effect, the value of pH_susp cannot be regarded as an adequate measure of soil acidity.     

Microbial complexes of hydromorphic soils in the Selenga River delta (Baikal region)

The number and the biomass of microorganisms were determined in the soils of the floodplain and islands in the Selenga River delta. The population of fungi in the soils studied was low. The number of saprotrophic prokaryote microorganisms varied from 10⁶–10⁸ CFU/g of soil in the upper horizons to 10⁴–10⁵ CFU/g in the lower horizons of the soils. This pattern is typical for most zonal soils. The microbial biomass in the floodplain soils was 2–4 times as high as that in the soils of the islands. The number of microorganisms of different ecologic-trophic groups participating in the nitrogen and carbon mobilization was much lower than that in the hydromorphic soils of the Transbaikal region or in the cryogenic soils of the Angara River basin (Irkutsk district). The low coefficient of microbiological mineralization and the low coefficient showing the lack of nitrogen (coefficient of oligotrophness) in the soils indicated the weak processes of organic matter decomposition in the soils studied. During the season investigated (August–September), the bacterial complexes in all the soils were dominated by bacteria of the genera Bacillus, Pseudomonas, and Aquaspirillum. In the floodplain soils, streptomycetes constituted a considerable part of the microbial complexes of the floodplain soils, whereas, in the soils of the islands, their number was minor.     

Vesicular-arbuscular mycorrhizal status of various crops in different agricultural soils of northern Greece

Summary This paper reports the results of a survey of the occurrence of vesicular-arbuscular mycorrhizas and spores of the associated fungi in a variety of soils in Northern Greece. The roots of several crop species were examined for the presence of mycorrhizal structures and all samples showed evidence of infection, though to varying degrees. Cotton plants, in particular, had heavy arbuscular infection. Intact and presumably viable spores were relatively infrequent and empty non-viable spores were much more common. Soil characteristics at each sample site are reported also, but only broad generalizations are made at this stage with respect to correlations between mycorrhizal occurrence and edaphic factors.     

Neoformations (Nodules and Placic Layers) in Surface-Gleyed Loamy Sandy Soils of the Northern Part of the Tambov Plain

Eurasian Soil Science - In the middle part of the profiles of light gray soils (non-gleyed, deeply gleyed, weakly and strongly gleyed) on silty loamy sandy two-layered deposits of the river...     

Phosphate fractions in some tanzania soils

Inorganic-P fractions were determined in 17 soil profiles from eight soil orders widely occurring in Tanzania. Most of the inorganic-P fractions decreased with depth. Where soils were young, or calcareous, or the parent material rich in phosphorus-bearing minerals, Ca-P was the dominant inorganic-phosphorus fraction. Where the soils were highly weathered, Al-P and Fe-P were the dominant fractions.