Volume 49, Nº 2 (2016)

The mineralogical composition of coarse fraction and characteristic features of the micro- and submicrofabrics and chemical composition of desert varnish on gravels of desert pavements and the underlying vesicular crust soil horizons were studied in the extremely arid soils of the Mojave (USA) and Trans-Altai Gobi (Mongolia) deserts. A set of common diagnostic features of elementary pedogenetic processes was identified in the automorphic desert soils developed on ancient (70–90 ka) piedmont plains composed of alluvial deposits with the high content of red-earth clay. The results of this study attest to the long and complicated history of the extremely arid soils with alternation of the humid and arid phases of pedogenesis reflected in a specific combination of textural (clay-illuvial) and carbonate pedofeatures and in the distribution patterns of iron, manganese, titanium, and barium in different layers of the desert varnish. The chemical composition of the latter did not depend on the mineralogical composition of the underlying substrates and was formed with active participation of soil microorganisms. This allowed us to conclude about the polygenetic (accretionary–microbiological) nature of desert varnish.

A methodology for comparing soil map of different dates in order to reveal changes in the soil cover is discussed. The analysis of a set of the maps of soil salinization on one of the farms in the Golodnaya Steppe region of Uzbekistan is used as an example. It is shown that traditional methods of comparing two maps developed in different years (normally, with an interval of five years and more) are low informative for the assessment of soil salinization dynamics. The suggested methodology assumes simultaneous analysis of several maps in order to reveal the trends in soil salinization. However, even in this case, the obtained results do not adequately characterize the dynamics of soil salinization on irrigated fields. It is argued that the direction of soil salinization–desalinization processes is an improper characteristic in this case. In order to understand the dynamics of soil salinization, the maps showing the dynamism of soil salinity and the maximum changes in the degree of salinity can be applied. A series of the compared maps make it possible to describe the changes in the soil cover related to salinization–desalinization processes. The high dynamism of these processes against the background of a virtually stable pool of soluble salts in the 1-m-deep soil layer is shown for the considered farm.

Structural changes of gibbsite at the binding of phosphate anions from NH₄H₂PO₄ solutions of different concentrations (from 10^–6 to 2 mol P/L) have been studied using an X-ray diffractometer and an electron scanning microscope with a spectrometric microanalyzer. It has been shown that, beginning from a concentration of 10^–3 mol P/L, the binding of phosphate anions has been accompanied by the release of anionic aluminum–phosphate complexes into the liquid phase. The content of these complexes has increased with the phosphate solution concentration and the time of its contact with gibbsite. The treatment of gibbsite with a 1 M phosphate solution for two months has resulted in the pronounced dissolution of the gibbsite crystal surface, accompanied by the formation of ammonium taranakite (ammonium salt of complex aluminophosphoric acid). Successive changes in size and form of the initially formed ammonium taranakite crystal has occurred in a 2 M phosphate solution. The degradation of the layered structure of taranakite and the enrichment of degradation products with phosphorus and nitrogen have been revealed. The significant increase of the P/Al ratios in the degradation products compared to the corresponding ratio in the initially formed taranakite indicates the formation of new phosphate phases resulting from the transformation of taranakite under the impact of free phosphate anions in a high-concentration solution.

The applicability of radiometric survey of soil profiles in the infrared range for the analysis of soil physical properties was studied. Radiometric data were obtained for different dates of the growing season for a number of soil profiles. The specificity of temperature profiles of texture-differentiated soils (Luvisols and Retisols) as related to weather conditions of the growing season was examined. The correlation analysis showed a close relationship between the air and surface soil temperatures and between the radiometric and thermodynamic soil temperatures in the upper 10 cm. In the studied profiles, the gradient of radiometric temperatures reached 0.5–0.8°C/cm in the humus horizons and sharply decreased at the depth of more than 15–20 cm. The gradient analysis of radiometric images made it possible to outline the boundaries of soil horizons. For the texture-differentiated soils, the most distinct boundaries were established between the gray-humus AY horizon and the underlying eluvial EL horizon in podzolic soils and between the AY horizon and the underlying humus-eluvial AEL horizon in gray soils.

In the sor (playa) solonchaks of chloride and sulfate–chloride salinity (the content of readily soluble salts is 0.9–1.0%) in the delta of the Khara River discharging into Lake Elton, the number of mycelial actinobacteria (actinomycetes) is low ((2–3) × 10³ CFU/g of soil). At a distance from the water’s edge, these soils are substituted for the light chestnut ones, for which an elevated number of actinomycetes (an order of magnitude higher than in the sor solonchaks) and a wider generic spectrum are characteristic. The actinomycetal complex is included the Streptomyces and Micromonospora genera, whereas in the sor solonchaks around the lake, representatives of Micromonospora were not found.

The effect of regular and periodic irrigation on the fertility and productivity of an ordinary chernozem cultivated under different conditions within the same cereal-fodder crop rotation is discussed. The investigation object is located in the area of the Azov irrigation system on the second terrace of the Don River in Rostov oblast. Irrigation water for the system is taken from the Veselovsk water reservoir. Its salinity is 1.7–2.1 g/dm³, and the salt composition is sulfate–sodium. The field experiments were performed in 2006–2013 on three experimental plots. Two of them were regularly irrigated; the third plot was periodically irrigated with alternation of 2-year-long periods with and without irrigation. Our study proved that periodic irrigation could be applied in the chernozemic zone. This new irrigation mode contributes to the preservation of the natural soil-forming process and stops the development of unfavorable processes typical of the lands irrigated with water of inadequate quality. In eight years of cultivation of the ordinary chernozem with periodic irrigation, the soil humus content increased by 10% (from 3.80 to 4.15%), and the yield reached 66.0 t/ha of fodder units. This was 9% higher than the yield obtained upon regular irrigation without agroameliorative measures and 12% lower than the yield upon regular irrigation in combination with soil-protective measures. Our data suggest that periodic irrigation is promising for the chernozemic zone, because it ensures lower water loads and preservation of the irrigated chernozems.

Indices characterizing the enzymatic activity of soils and the contents of aliphatic and polycyclic aromatic hydrocarbons have been applied for estimating the efficiency of remediation of oil-polluted soils in the north of European Russia. Oil-polluted test plots treated with the Universal and Roder biopreparations and subjected to the agrochemical reclamation have been examined. The suggested indices can be used to diagnose and monitor the oil-polluted soils and to assess the efficiency of their remediation.

Region near Głogów is characterized as industrial—agricultural area, intensively used. Presented study was undertaken to estimate the impact of agricultural land use and the vicinity of Głogów copper smelter on the contents of available forms of magnesium, phosphorus and potassium in selected profiles of Luvisols. The following analysis were performed: soil particle-size distribution, pH, organic carbon contents, CaCO₃ contents. The contents of available forms of phosphorus and potassium were determined by Egner- Riehm method and that of magnesium using Schachtschabel’s method. The results of the study showed that the contents of available P is medium (III class of abundance), very low in K (V class) and for available Mg very low (V class) to medium for surface horizons and very high (I class of abundance) in other soil horizons. The soils, in spite of the elevated copper content in humus horizons, according to IUNG, were classified as uncontaminated soils, therefore, can be used in plant production for all types of crops.