The current state of salinity of irrigated soils in the area of the Sarpinskaya hollow in the Caspian lowland has been studied, using the example of the Duboovrazhny irrigated plot in the Volgograd region. At the peak of irrigation in the 85-90s of the last century, forage grasses were cultivated on the plot, irrigation was carried out by sprinkler irrigation, the groundwater level remained satisfactory, and there were no foci of secondary soil salinization. Currently, the plot is a private farm, where melons and vegetables are grown using drip irrigation, the groundwater level remains satisfactory with local formation of temporal water saturated layer. To identify the features of the process of salinization in irrigated soils in the Sarpinskaya hollow based on the materials of the field work performed in 2018–2019, a model of two-dimensional distribution (depth, distance) of the activity of ions (Ca²⁺, Cl^–, Na⁺) over several profiles along weakly concave low ranges and elongated hollows between them and across relief wave was created. It was revealed that natural soil salinization predominates in the study plot mainly deeper than 1 m, and results from shallow bedding of Khvalynian chocolate clays at ranges. Solonchakous soils occur in elongated hollows between ranges where surface and subsurface runoff water is accumulated and natural drainability is low. Residual traces of soil secondary salinization expressed in the presence of calcium chloride in the soil solution were found. The maximum values of salts and exchangeable sodium are concentrated in the deeper part of the soil profile. 

Soil samples and physical size-density fractions isolated from them (silt particle size less than 1 µm, light fraction (LF) with a density of less than 2 g/cm³ and a fraction of the residue) of ordinary chernozem were studied in three contrasting variants of the experimental fields of the Kamennaya Steppe agrolandscape of the Voronezh region: mowed steppe, long-term permanent bare fallow and permanent corn – the main differences of which are in tillage (cultivated and not cultivated lands) and in the supply/absence of plant residues and root secretions. The LF content changes in the series: “mowed steppe” > “permanent corn” > “permanent bare fallow”, which corresponds to the direction of changes in the total carbon content of the soil and a decrease in the value of the contact angle of wetting (CA) of the surface of the solid phase of the studied chernozems. The determination of the total C and N content revealed the change in the qualitative and quantitative composition of the size-density fractions for different land use cases. Chromatographic fractionation of alkaline extractions of humus substances (HS) of chernozem samples and size-density fractions revealed an increase in the degree of hydrophilicity of HS while simultaneously increasing the hydrophobicity of the solid phase surface and the carbon content in the soil. HS of LF of the “mowed steppe” turned out to be by 63% more hydrophilic than HS of LF of “permanent bare fallow” and by 47% more hydrophilic than HS of LF of “permanent corn”. While the hydrophilicity of the HS silt differed by 16 and 27%, respectively. The hydrophilicity of the HS of the original soil in the plot of the “mowed steppe” was by 41% higher than the hydrophilicity of the HS in the soil in the plot of “permanent bare fallow” and by 24% higher than in the soil of the plot of “permanent corn”. In addition, changes in the hydrophilicity of HS of size-density fractions are more intense than the HS of the soil, so the change in the degree of hydrophilicity of HS of size-density fractions is an indicator of soil degradation under different agrogenic pressue.

The paper deals with morphological properties of agrogenically transformed chestnut soils of slope lands in the south of the Volga upland within the urban landscape of Volgograd. It is established that as a result of agrogenesis, erosion, land use change, as well as of agroforestry reclamation measures performed, both anthropogenic deeply transformed and postagrogenic soils have been formed. The greatest changes under the influence of agrogenesis are noted in morphological structure of profiles. Agrogenesis results in degradation of soils involved in active agricultural use due to intensified sheet and rill erosion. In eroded soils there is noticed a decrease in the thickness of agrohumic layer, formation of furrow bottom compaction and changes in structure. Their characteristic feature is the presence on the surface of a homogeneous agro-abraded horizon with lumpy structure, in the lower part of which secondary carbonates inherited from the carbonate horizon and resulted from deep plowing may occur. Soils slightly exposed and not exposed to erosion processes have an agrohumus horizon on the surface, which depending on soil tillage can have thickness from 19 to 36 cm. At present, the annual agricultural practices at the plot include mowing of weeds and disk plowing to 20 cm depth. Earlier moldboard plowing to 40 cm depth was performed. All agrogenically-modified soils are characterized by HCl reaction with carbonates from the surface. Carbonate accumulations in agrogenic soils, as a rule, have a segregated form that indicates rapid summer drying of the profile and short period of soil solutions migration. Upper boundary of accumulative-carbonate horizons of agrogenic soils on the average is at 42 cm depth. Such occurrence of carbonate horizons in general is typical both of natural non-eroded soils of dry-steppe zone and of soils involved in agricultural land use. Under forest plantations the original chestnut soils were transformed into turbated agrozems due to deep ameliorative cultivation preceded planting of woody and shrub vegetation. Soil preparation practices applied before tree species planting resulted in transformation of original chestnut soils into turbated agrozems, which is due to deep (up to 60 cm) soil reclamation. The forest belt, being a “barrier” between the field parts, contributed to the formation of a stratified small horizon (trait) of 10 cm thickness for more than 70 years due to the constant inflow of fine-grained soil and decay of leaf and herbaceous debris. 

The article is based on a long-term study of floodplain soils of the Amur River valley within the north-eastern part of the Middle-Amur Lowland. The results of field work on the soil-geomorphological profile across the Slavyansky Island, located 200 km from Khabarovsk down the Amur River, are discussed. The study analyzes the occurrence of the island's floodplain soils on riolkas[1] and their properties, with an emphasis on morphology and lithological and particle-size composition. The features of soil formation on riolkas of different genesis – alluvial and aeolian – are shown. On sandy and sandy-loam deposits of alluvial riolkas (“meadow-forest” ridges) poorly developed sod gley soils are formed. On heavy loam and clay alluvium of the “meadow“ ridges, annually flooded by river waters, sod-meadow gley soils develop under the woodreed grass stand. Sand deposits of high aeolian riolkas are characterized by a homogeneous fine-grained structure without interlayers, signs of organic matter and with a significant amount of mica. They describe poorly developed sod-forest soils under high-trunk oak forests. The formation of texture-differentiated soils on all types of riolkas was not revealed. When the floodplain reaches the position of the first terrace above the floodplain, the differences in the lithological composition and particle-size distribution, soil texture, height above the water edge and the nature of vegetation on the inherited riolkas provide a multidirectional evolution of soil formation. At the same time, the development is taking place in accordance with the zonal types of soils (sod-forest, brown-earth, texture-differentiated – soil with a bleached horizon (podbel)). The last are mainly formed on clay-loam alluvium, which can overlay not only alluvial, but also some aeolian riolkas.

[1]Riolkas are ancient, relatively high sand ridges (extended dunes) with plant cover found in Amur region (Russian Far East).

Based on the results of field experiments carried out in the nursery of Michurin garden of Russian State Agrarian University named after K.A. Timiryazev, rational irrigation schedules for apple-tree seedlings of different age (1-, 2- and 3-year-old) were developed and scientifically substantiated. Excess water was diverted from the experimental plot by underground drainage system, and the drip irrigation system was used for watering plants. With its characteristic low rate of water usage and highly frequent irrigation applications it allows the moisture content to be maintained within a narrow range. The effectiveness of irrigation schedules was evaluated by the response of seedling – their biometric characteristics, determining the productivity of apple trees in orchard in future, such as average plant height, stem diameter at 20 cm height, leaf surface area, which were measured. The amount of high-quality planting stock was recorded in each variant as well. In order to btain 1-year-old apple seedlings it is recommended to maintain soil moisture within the range of 70–90% of field capacity (FC). This irrigation schedule results in the maximum amount of standard planting stock (1-st and 2-nd category) – 25.9 thousand seedlings per ha, with the average leaf surface area of 1 468 cm², trunk diameter – 1.8 cm, plant height – 140 cm. For 2- and 3-year-old seedlings the differentiated irrigation schedule was developed, whereby the moisture content and depth of the wetted layer varies as the root system grows. In the first year of growth soil moisture should be maintained within the range of 70–90% FC in 0–30 cm layer because of the poorly developed root system; for 2- and 3-year-old nurslings soil moisture can be reduced to 60–80% FC in 0–40 cm and 0–50 cm layer respectively. The height of 2-year-old seedlings was on average 174 cm, leaf surface area – 3 715 cm², stem diameter at 20 cm height was 2.3 cm, the amount of standard planting stock was 25 thousand seedlings per ha. The 3-year-old seedlings reached the height of 214 cm, were characterized by leaf surface area of 5 973 cm², stem diameter at 20 cm of 2.8 cm, the yield of standard seedlings was also 25 thousand seedlings per ha. Moreover, for two variants of irrigation (60–80% FC and 70–90% FC) moisture distribution contours immediately after irrigation, 24 hours after irrigation and before the next irrigation application were designed. The areas of segments with different moisture content in vertical section of contours were calculated, thus, revealing the character of moisture distribution down the soil profile and allowing performance of comparative characteristic of irrigation schedules. The obtained wetting contours indicate the absence of unproductive losses of irrigation water for infiltration into the underlying horizons when the considered drip irrigation schedules were applied.

This paper assesses the relationship between the physico-chemical and agro-chemical properties of sod-podzolic soils in the Moscow region and ordinary heavy-loamy chernozems in the Krasnodar region within the catenas and down the soil profile. Soil properties changed significantly through seasonal dynamics. From the end of April to the middle of June in the soil solution of sod-podzolic soils, the value of Eh varied from 534 to 759 mv, the ratio of NO₃/NH₄ – from 0.2 to 15.4; the content of water-soluble manganese – from 4.0 to 10.1. At the same time, there was a delay in change of soil properties, as humidity and temperature varied. It is shown that in different intervals of soil properties between individual indicators of fertility, the effects of synergism and antagonism are manifested. The degree of mutual influence of soil properties depended on both the degree of soil fertilization and the degree of their cultivation. Information relationships were manifested not only between the soil properties, but also between the processes. Temporary excessive moistening of the soil led to acidification of the soil in the washing type of water mode, and to alkalinization in the non-washing type. It is proposed to account for the relationship of soil properties with humidity, temperature, pH, and Eh to adjust the components of farming systems.