Changes in the morphological properties of chernozems of Rostov oblast in the area of landfills

The transformation of soil morphology in the area of landfills is caused by the technogenic disturbance of the soil profile; artificial soil compaction; local soil waterlogging and the development of hydromorphism; the removal of heterogeneous deposits from the body of reclaimed landfills and their accumulation in the subordinate landscapes; and the gleyzation and production of biogases in primitive soils developed from the new substrate. Various combinations of these processes result in the formation of several different morphological types of the soil profile.     

Information about the V Congress of the Dokuchaev Soil Science Society

Chronicle

Information about the V Congress of the Dokuchaev Soil Science Society     

Aggregate Composition as Related to the Distribution of Different Forms of Carbon in Soils of Rostov Agglomeration

Eurasian Soil Science - The aim of this work was to study the transformation of soil structure in the course of urban pedogenesis and to assess the relationship between the size of aggregates and...     

Physical Properties of Urban Soils in Rostov Agglomeration

Transformation of particle-size composition, structure, and density of soils upon urbopedogenesis is considered for Rostov agglomeration. Various soils are compared by horizons. It is found that the share of sand fractions increases in upper and middle horizons of migration–segregation chernozems (Calcic Chernozem (Hyperhumic, Loamic)), above all, at the expense of particles of 0.05—0.001 mm in size; with the coarse medium sand fraction 1–0.25 mm being diagnostic for urbopedogenesis. The reason is the introduction of sandy particles upon urban construction, arranging water conduits and other utility lines, as well as the use of icing-control sandy mixtures. The Dolgov-Bakhtin schedule appears to be the most appropriate for assessing the structure of urban soils. Dry sieving testified to the decreasing amount of agriculturally valuable aggregates in all compared pairs of horizons in the sequence of urban soils: under forest vegetation → under steppe vegetation → in the buried massif of urbosoils. The water stability of aggregates decreases in the sequence: soils under steppe vegetation → buried horizons of urbosoils → soils under forest vegetation. The following sequence of urbic horizons (UR and RAT) shows a decrease in the share of agriculturally valuable fractions and an increase in their water stability: heavy-textured UR → light-textured UR → RAT. The density of natural soils varies insignificantly within the city territory, with its urbostratified soils (Calcic Chernozem Novic (Technic Loamic) in residential areas often manifesting the maximal density.     

Changes in the soils of solonetzic associations in 30 years after their reclamation with the use of moldboard plowing,deep tillage with a three-tier plow,and deep rotary tillage

Changes in the properties of solonetzic soil associations (chestnut solonetzic soils and chestnut solonetzes) in the dry steppe after their reclamation have been studied for 30 years. The reclamation included the deep three-tier plowing and the approach of rotary tillage. A single rotary tillage operation resulted in the formation of fine aggregates of equal sizes in the plow layer; any morphological features of the restoration of solonetzic pedogenesis are absent. The atmospheric moisture easily penetrates into the soil, and soluble salts are leached off to a great depth. In 30 years since the soil amelioration with the use of a PMS-70 rotary tiller, the humus content has increased up to 3.3% in the upper 20-cm-thick layer and up to 2.4% in the layer of 20–40 cm. The content of adsorbed Na⁺ in the 20- to 30-cm-thick layer has decreased to 10.6% of the cation exchange capacity (in comparison with 19.8% in the nonreclaimed soil). The spatial heterogeneity of the soil cover has decreased in comparison with that prior to the reclamation. During the entire observation period, crop yields gained from the fields reclaimed with the use of the rotary tiller have been by 25–60% higher in comparison with those on the fields with traditional treatments.     

Molecular structure of humus acids in soils

The molecular structure of humus acids remains one of the most challenging issues in the soil science. The focus of the current research lies in defining the molecular and supramolecular structure of soil humus acids. This paper provides a brief review of the current understanding of the problem and shares findings of the elemental and X‐ray structural analysis of humic and fulvic acids extracted from Chernozems and Chestnut soils in the Rostov region. This region occupies a large area of the South‐European Russia. Humic acids in the studied soils have reduced carbon content compared to average parameters for these soil types. The supramolecular organization of humic acids in three‐dimensional space contains two to four layers of condensed aromatic systems supplemented by a network of chain fragments of different regularity and length. Parameters of this structure vary for soils of different genesis and genetic horizons. However, interplanar distances are fixed in the range of 0.349 to 0.371 nm. Thickness of the carbon network band increases with the benzoidicity level of humic acids. The obtained results confirm the specific matrix structure of humic acid molecules. Considering currently available scarce data these findings are valuable and unique. Our findings are consistent with the general hypothesis about the supramolecular nature of humic substances.     

Use of Background Concentrations of Heavy Metals for Regional Monitoring of Soil Contamination by the example of Rostov Oblast

Eurasian Soil Science - In the monitoring of soils contaminated with heavy metals, the choice of the target indicators (background or threshold values) is a challenging task. The determination of...     

The humus state of the soils of locally hydromorphic landscapes in the lower reaches of the don river

The humus state of rainfed chernozems affected by local waterlogging was studied. The total humus content in the hydromorphic chernozems increases, as well as the content of fulvic acids, whereas the content of nonhydrolyzable residue (humin) decreases. A significant increase in the portions of the third fractions of humic and fulvic acids is observed. The role of the fine silt and clay fractions in the binding of humic substances increases in the lower horizons of locally hydromorphic soils. The increase in the content of fulvic acids (fulvatization) is mainly due to their predominance in the clay fraction. The latter is specified by the significant narrowing of the C_ha-to-C_fa ratio, the lower content of the nonhydrolyzable residue, and the increased content of the clay-bound (3rd fraction) fulvic and humic acids. The composition of the humus in the fine silt fraction of the studied soils is characterized by an increased amount of humic acids of the second fraction with a decrease in the relative content of fulvic acids.     

Inclusion of soils and soil-like bodies of urban territories into the Russian soil classification system

The results of the Internet discussion on the classification of urban soils aimed at evaluating their possible inclusion into the modern Russian soil classification system adopted by a wide range of specialists are presented. The first step was to address the urban diagnostic horizons as the basis for identifying soil types according to the rules of the Russian soil classification. New diagnostic horizons were proposed for urban soils: urbic (UR), filled compost-mineral (RAT), and filled peat (RT). The combination of these horizons with other diagnostic horizons and layers of technogenic materials correspond to different soil types. At the subtype level, the diagnostic properties (qualifiers) that may reflect both natural phenomena (gley, alkalinity) and technogenic impacts on the soils (urbistratified; phosphatic; or poorly expressed urban—ur, rat, rt) are used. Some corrections were proposed for the system of parent materials in urban environments. Urban soils formerly described in another nomenclature—urbanozems, urbiquasizems, and culturozems—are correlated with the taxa in all the trunks of the system. The proposals accepted can be used for the next updated version of the new Russian soil classification system.     

Effect of humic preparation on winter wheat productivity and rhizosphere microbial community under herbicide-induced stress

Purpose

The aim of the present work was to study the effect of humic preparation on the yielding capacity of winter wheat, the dynamics of mineral nutrients in the rhizosphere, and the activity of rhizosphere microbial community, as well as the protective properties of humate treatment under the stress caused by the application of a sulfonylurea herbicide.

Materials and methods

The humic preparation BIO-Don is prepared from vermicompost by alkaline extraction. The effect of humic preparation was estimated in a field experiment. The contents of the mobile ammonium and nitrate, exchangeable potassium, phosphorus, and humus were determined. Sampling and nutrient determination were performed in the tillering, booting, and grain maturing stages. Production experiments on the study of the combined effect of the humic preparation and the sunfonylurea pesticide Granstar Pro were performed in 2015 and 2017. The dynamics of mobile phosphorus in soil was studied. The abundance of culturable bacteria in the rhizosphere and bacterial species with different ecological strategies was determined. The dominant bacterial species were identified by MALDI-TOF mass spectrometry.

Results and discussion

The results of a small-plot experiment showed that at the tillering stage, the use of humic preparation has led to significantly higher supply of soil with mobile phosphorus. The winter wheat yield was 32.0 dt/ha in the control and 39.2 dt/ha with humic preparation or 22.5% gain in yield. The results of production experiment show that the application of sulfonylurea herbicide induced a chemical stress on winter wheat plants, but the use of humic preparation reduced this effect and increased the availability of phosphorus compounds. The treatment of plants with pesticides caused the general decrease in abundance of bacteria in the rhizosphere. The effect on quickly growing bacteria is more pronounced, while slowly growing bacteria and fungi are more resistant to this impact.

Conclusions

The application of humic preparation to winter wheat plantations allows to decrease the toxic effect of sulfonylurea herbicide, improve the supply of soil with mineral nutrients, and increase the crop yield. The favorable effects of humic preparation can be related to the active regulation of phosphorus mobilization by plants through the mechanism of root exudates due to the activation of root microbiota.