Phosphate status of chernozem-like hydromorphic soils in the northern Tambov Plain

The phosphate status of chernozem-like soils in the northern forest steppe of the Tambov Lowland depends on soil waterlogging and hydrological conditions. Due to surface waterlogging and free effluent seep-age in podzolized, chernozem-like soils of open watershed depressions, the removal of bases and iron decrease the total phosphorus content by 10–15% because of the decrease in active mineral phosphates. Organic matter acts as a buffer preventing phosphorus from leaching. In podzolized, chernozem-like and podzolic, gleyic soils of closed watershed depressions, significant amounts of iron phosphates are accumulated in fine earth and ortsteins due to surface waterlogging and difficult effluent seepage. Under ground waterlogging, calcium phosphates prevail in the composition of active mineral phosphorus in the gleyed, gleyic, and gley chernozem-like soils of above-floodplain terraces.     

Genesis,hydrology, and properties of soils in mesodepressions waterlogged by surface water in the northern Ryazan forest-steppe

On the interfluves and in small depressions of the Ryazan forest-steppe, under periodic stagnation of surface water, acid chernozem-like soils with a relatively thick humus horizon, podzolic horizons, and marble-colored gleyed B1 and B2 horizons are formed. The eluvial horizons of these soils contain Mn-Fe nodules, and dark humus coatings occur in the illuvial horizons. In the spring, the eluvial horizons of these soils are excessively moistened and gravitational water stagnates on the soil surface for 3–4 weeks. The formation of the acid light-colored eluvial horizons of the soils on leached rocks is related to gleying under the conditions of the stagnant-percolative regime. Their total thickness is 15–25 cm and more. According to the properties of their solid phase, these horizons are similar to the podzolic horizons of soddy-podzolic gleyed soils. These soils have not been represented in the classification systems of soils of the USSR and Russia. Based on the principles of the substantial-genetic classification, one of the authors of this article [9] referred this soil to gleyed podzolic chernozem-like soils, thus, considering it as an individual genetic soil type. The gleyed podzolic chernozem-like soils differ from the leached chernozems by their low productivity and difficulty of tillage. In humid and moderately moist years, the death of crops or a reduction in yield are probable because of the excess of moisture.     

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.     

Solods of the Baraba Lowland and the Priobskoe Plateau: Their properties and genesis and the methods of their diagnostics

The properties, hydrological features, and genesis of the solods occurring in the Baraba Lowland and Priobskoe Plateau were studied. Methods for determining the hydromorphism degree are considered; the features of the similarity and differences between the solods and other soils with textural profile differentiation are shown. Depending on the reasons for the waterlogging, the solods should be divided into two groups: the solods of groundwater waterlogging and the solods of surface waterlogging. Criteria for their discrimination are suggested: the ratio between the contents of the clay fraction in the parent rock (or in the B2 horizon) and that in the A2 horizon, the changes in the pH values along the soil profiles, and the content of nonsilicate iron compounds. The solods studied are shown to be formed under the conditions of a stagnant-percolative regime and gleying. This circumstance is an obligatory and sufficient reason for the formation of the light-colored acid eluvial (A2) horizons. According to some basic properties of the soil solid phase (the acidity, the total chemical composition, and the clay pattern in the eluvial part), the gleyed solods are close or identical to the gleyed soddy-podzolic and gleyed chernozem-like podzolic soils. At the same time, the solods differ from the gleyed chernozem-like podzolic soils by their thicker A1 (or Ap) horizon and their higher humus content (5–7%).     

Roles of iron and clay in Genesis of acid soils under a humid,temperate climate

The occurence of acid brown soils, podzols and podzolic soils, and the intermediate types of ochreous brown and brown podzolic soils over arenaceous granite in Vosges was closely correlated with the contents of iron rather than with calcium plus magnesium in the parent materials. Acid brown soils were associated with high and podzols and podzolic soils with low contents of iron, the limiting value being near 5 percent. Additional investigations in beech forests of soils derived from a variety of acid rocks indicated that contents of iron and clay in the parent materials controlled the type of humification of litter. With higher contents of iron and clay, humification gave rise to mull. With lower contents, mor or moder was formed. The nature of humification was believed responsible for tilting pedogenesis toward brunification or toward podzolization. In brunification, the clay-iron-humus complexes that are formed tend to be immobile and promote formation of crumbly structure. The “active iron” occurs as films around clay particles and thus links them to humus. In podzolization, on the other hand, the complexes formed are of humus with iron or aluminum but without clay. These are mobile and are translocated downward in profiles to form spodic horizons. The organo-metal complexes in ochreous brown and brown podzolic soils are mobile to only a limited extent. The combined results of these investigations demonstrate that contents of iron and clay rather than calcium in parent materials determine the pathway of pedogenesis from acid rocks under humid, temperate climates.     

Forms of acid hydrolysis and gley formation and their role in the development of light-colored acid eluvial (Podzolic) horizons

Nowadays, three processes, namely lessivage, acid hydrolysis, and gleying, are considered as responsible for the development of loamy and clayey podzolic soils. However, as was shown earlier, lessivage is not obligatory for their origin. In view of assessing the reasons for the formation of light-colored acid eluvial horizons, this article deals with the role of acid hydrolysis under aerobic conditions against the background of a percolative water regime and of two forms of gleying in the development of the horizons mentioned above. One form of gleying occurs under permanent anaerobic conditions against the background of a stagnant water regime; the other one is formed under pulsating anaerobic-aerobic conditions against the background of a stagnant-percolative water regime. As a result, three large genetically individual groups of soils are formed: nondifferentiated brown and gley, and differentiated podzolic soils on different parent rocks. The two latter forms of gleying are identical in their effects on the mineral substrates. They cause the iron removal from the soils. Among the three processes considered, the last one (gleying under a stagnant-percolative water regime) is the single reason for the leaching of most of the metals, the formation of light-colored acid eluvial horizons and their clay depletion, and for the differentiation of the soil profile.     

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.     

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.     

The soil cover on a gentle watershed slope under conditions of the recent seasonal soil overwetting in the Kamennaya Steppe area

The soil cover pattern on a gentle watershed slope at the Kamennaya Steppe Experimental Farm consists of the areas of typical chernozems, zooturbated chernozems, and leached chernozems evolving into chernozemic-meadow soils; they are oriented along the slope. This soil combination is complicated by the presence of slightly eroded and slightly saline soils. The seasonal overwetting and inundation of the soils are favored by the discharge of the groundwater above the local aquiclude represented by the layer of dark brown calcareous clay at the depth of 1.0–2.2 m from the soil surface and by the concentration of snowmelt runoff in the concave parts of the slope. Seasonal overwetting of the soils leads to the appearance of olive tints and small iron concretions (quasigley features) in the lower horizons; in some cases, proper gley features (bluish coatings) appear in the chernozems. The veinlets of powdery gypsum are formed in the middle-profile horizons of some soils. Salt efflorescence on the surface in some places is also the result of the seasonal overwetting of the soils followed by their intense drying upon the hot and droughty weather conditions.     

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.     

Development of hydromorphism in soils of agrolandscapes in the depressions of Western Ciscaucasia

The current state and rate of hydromorphism development in the soils of flat bottomed depressions in Western Ciscaucasia are assessed. The dynamics of the soil cover pattern on a plain with numerous mesoand microdepressions and on a watershed with weakly pronounced erosion relief were revealed. The relationship between the expansion of the waterlogged areas and the pattern of the soil cover of the agrolandscapes in the depressions was revealed. The dependence of the areas of excessively moistened sites on the changes in the topography was shown. The direction and parameters of the changes in the morphology, chemical composition, and hydrological properties of the degraded hydromorphic soils were investigated. The relationships between the density of the soils and the humus content and the composition of the exchangeable bases were studied. Methods for the assessment of the rates of the degradation processes based on the comparison of aerial photographs and soil maps for typical sites in the territory investigated are proposed. The specific features of decoding the aerial photographs of the soils in the depressions were revealed. The relations between the differences in the photos’ tone and the degree of the hydromorphic degradation of the soils were found. Promising methods for interpretation of aerial photographs with the help of image analysis programs can be recommended.     

Fractional-Isotopic Composition of Lead Compounds in Soils of the Kologrivskii Forest Reserve

Isotopic composition of lead is a very sensitive indicator allowing us to determine even very low contamination of soils by this element, which is not noticeable from the change in its concentration against the background of the natural variability. Isotopic composition of loosely bound lead fractions (exchangeable and specifically sorbed) changes in soils of the Kologrivskii Forest State Natural Reserve under the impact of global or regional atmospheric transport and deposition of contaminants, though these soils are not subjected to the local technogenic pollution. The maximum portion of lead bound with the soil organic matter in the upper organic horizons reaches 75% of the total lead content. The portion of lead bound with iron and manganese (hydr)oxides increases down the soil profile. The portion of the residual fraction of lead also increases significantly down the soil profile. The most pronounced changes are observed for the ²⁰⁶Pb/²⁰⁷Pb ratio, which decreases from 1.20–1.24 to 1.15–1.18 under the impact of global pollution. The technogenic compounds of lead migrate down the soil profile. In the gray-humus gley alluvial soil (Fluvic Gleysol), low values of the ²⁰⁶Pb/²⁰⁷Pb ratio are observed for the exchangeable and specifically sorbed lead fractions in the entire soil profile, which is explained by the worse conditions for lead fixation in the profile of this soil in comparison with those in the podzolic soils.     

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.     

Acid-base buffering of soils in transitional and transitional-accumulative positions of undisturbed southern-taiga landscapes

The method of continuous potentiometric titration (CPT) of soil water suspensions was used to evaluate the acid-base buffering of samples from the major genetic horizons of podzolic soils on a slope and soddy gley soils on the adjacent floodplain of a rivulet. In the soils of the slope, the buffering to acid upon titration from the pH of the initial titration point (ITP) to pH 3 in all the horizons was 1.5?C2.0 times lower than that in the podzolic soils of the leveled interfluve, which could be due to the active leaching of exchangeable bases and oxalate-soluble aluminum and iron compounds with the later soil flows. In the soddy gley soils, the buffering to acid in the mineral horizons was 2?C10 times higher than that in the podzolic soils. A direct dependence of the soil buffering to acid on the total content of exchangeable bases and on the content of oxalate-soluble aluminum compounds was found. A direct dependence of the buffering to basic upon titration from the ITP to pH 10 on the contents of the oxalate-soluble aluminum and organic matter was observed in the mineral horizons of all the studied soils. The soil treatment with Tamm??s reagent resulted in the decrease of the buffering to acid in the soddy gley soils of the floodplain, as well as in the decrease of the buffering to basic in the soils on the slopes and in the soddy gley soils. It was also found that the redistribution of the mobile aluminum compounds between the eluvial, transitional, and transitional-accumulative positions in the undisturbed southern taiga landscapes leads to significant spatial differentiation of the acid-base buffering of the mineral soil horizons with a considerable increase in the buffer capacity of the soils within the transitional-accumulative terrain positions.     

Soil altitudinal sequence on base-poor parent material in a montane cloud forest in Sierra Juárez, Southern Mexico

The soils of montane cloud forests (MCF) are still insufficiently studied. A number of researchers report Podzols to be the main soil group for MCF ecosystems; however, a great deal of contradictory data exists. We studied an altitudinal sequence of soils formed on ferrous chlorite shale under natural MCF vegetation in Sierra Juárez, Southern Mexico, from 1500 to 2500 m asl. The soils of the upper part of the toposequence were Folic Stagnic Podzols, with inclusions of Folic Stagnosols in local depressions, while the soils of the lower part of the toposequence were Folic Cambisols (Humic, Hyperdystric). All the soils in the toposequence were extremely acid, and had thick organic surface horizon. Mineral horizons of all soils were poor both in exchangeable and total reserves of bases; the bases were concentrated mainly in organic topsoil. With decreasing altitude both the thickness of albic horizons, the depth of the maximum acid oxalate-extractable Fe and Al concentrations, and the difference in clay content between the eluvial and illuvial horizons decreased. In the upper part of the toposequence the composition of soil clays was similar to that of parent material (chlorite and mica), with some mixed-layered 2:1 minerals. However, gibbsite and kaolinite were also present in the soils of the other site within the same upper MCF belt. The phenomenon was ascribed to parent material heterogenity. In the medium and lower parts of the toposequence gibbsite and kaolinite were the dominant minerals. We consider that the main pedogenic processes in the study area are raw humus accumulation, weathering in situ, podzolization, and iron reduction due to water stagnation in mineral topsoil. The intensity of weathering decreases, while the extent of water stagnation increases with altitude. To a great extent the genesis and altitudinal distribution of the soils in the MCF depends on parent material.     

Characteristics of brown forest soils developed on the paleozoic shale in northern Kyoto with special reference to their pedogenetic process

Abstract

Morphological and chemical properties of brown forest soils and podzolic soils developed on paleozoic shale under beech and/or cryptomeria have been studied with special reference to the eluviation-illuviation characteristics of Fe and Al.

Mobilization of Al was observed even in brown forest soils and its pattern was similar to that in podzolic soils. Its intensity was higher in the brown forest soils developed on the ridge under cryptomeria than in those on the slope under beech. Hence, podzolization is considered to be one of the genetic processes involved in the brown forest soils in question.

Furthermore, the value of (Fep+Alp)/clay that is employed to define a podzolic B or spodic horizon indicated the presence of a podzolic B horizon even in the brown forest soils studied, while no spodic horizon was found even in the podzolic soils with a clearly recognizable albic horizon. Moreover, the examination of the degree of podzolization showed that the brown forest soils almost corresponded to Ochreous brown earths.     

Characteristics of Clay Minerals in Podzols and Podzolic Soils

The clay minerals in Podzols and podzolic soils developed under coniferous forests in the Subarctic and Cool-temperate zones are characterized by the predominance of smectite and/or mica-smectite interstratified minerals in the eluvial horizons and chlorite-vermiculite intergrade in the illuvial horizons. A large amount of vermiculite is present in the eluvial horizons of some podzolic soils in the Cool-temperate zone. The illuvial horizons of these soils also contain free iron oxides such as goethite. Imogolite and allophane are present in the illuvial horizons of several soils derived from volcanic ashes. It is suggested that the critical bioclimate for the release of interlayered aluminum from the 2:1-type minerals lies between the Cool- and Warm-temperate zone. In the eluvial horizons of Podzols and podzolic soils, mica minerals and chlorite, as primary minerals, have been transformed to smectite through the pedogenic process. Based on previous studies on the structure and degradation of the dioctahedral mica minerals, it is considered that smectite is transformed from 1M-type mica minerals directly, and from 2M-type mica minerals via mica-smectite interstratifled minerals. The formation of a smectite lattice in the eluvial horizon should be a clay-mineralogical indicator of podzolization.     

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.     

Podzolization as a deferralitization process: dynamics and chemistry of ground and surface waters in an Acrisol – Podzol sequence of the upper Amazon Basin

Hydrochemical processes involved in the development of hydromorphic Podzols are a major concern for the upper Amazon Basin because of the extent of the areas affected by such processes and the large amounts of organic carbon and associated metals exported to the rivers. The dynamics and chemical composition of ground and surface waters were studied along an Acrisol‐Podzol sequence lying in an open depression of a plateau. Water levels were monitored along the sequence over a period of 2 years by means of piezometers. Water was sampled in zero‐tension lysimeters for groundwater and for surface water in the drainage network of the depression. The pH and concentrations of organic carbon and major elements (Si, Fe and Al) were determined. The contrasted changes reported for concentrations of Si, organic carbon and metals (Fe, Al) mainly reflect the dynamics of the groundwater and the weathering conditions that prevail in the soils. Iron is released by the reductive dissolution of Fe oxides, mostly in the Bg horizons of the upslope Acrisols. It moves laterally under the control of hydraulic gradients and migrates through the iron‐depleted Podzols where it is exported to the river network. Aluminium is released from the dissolution of Al‐bearing minerals (gibbsite and kaolinite) at the margin of the podzolic area but is immobilized as organo‐Al complexes in spodic horizons. In downslope positions, the quick recharge of the groundwater and large release of organic compounds lead to acidification and a loss of metals (mainly Al), previously stored in the Podzols.     

Iron oxide and clay minerals and their relation to colours of red and yellow podzolic soils near Sydney,Australia

The iron oxide and clay minerals in some typical red and yellow podzolic soils from New South Wales have been investigated by X-ray diffraction and infra-red spectroscopy. The dominant iron oxide mineral is goethite containing about 13–14 mol % AlOOH, this being the mineral which gives the yellow soils their characteristic colour. The red soils also contain finely divided hematite which masks the colour of the goethite. Lepidocrocite was not detected in any of the soils examined. The dominant clay minerals are kaolinite and dioctahedral interstratified illite-smectite, the latter being more concentrated in the finer clay fractions, especially in soils developed on calcareous greywacke. In the red podzolic soil developed on Ashfield shale, illite-smectite is strongly interlayered with well-ordered aluminous material. Dickite occurs in this soil.