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The aim of this work is to evaluate recent changes in soil salinity status at the Generalovskaya irrigation system in the dry-steppe zone of Volgograd oblast of Russia on the second terrace of the Don River near the Tsimlyansk Reservoir. The studied area has not been irrigated since the mid-1990s. We have used materials of terrain soil survey of the area in 1990 and 2020; data on soil water extracts (1 : 5); measurements of the activities of Na+, Ca2+, and Cl– ions with ion-selective electrodes in soil pastes with a moisture content of 40–45%; and aerial photographs (1990) and satellite image (2020). The studied area was subjected to secondary soil salinization in the 1990s due to the groundwater rise above the critical level. In 25 years after the cessation of irrigation, the groundwater table has descended to a depth of more than 5 m, and secondary-saline soils have been subjected to a gradual desalinization with the development of alkalization in the topsoil. The current soil salinity status inherits the pattern that existed 25 years ago, i.e., the spatial distribution of salts in the studied landscape is generally preserved. We have revealed the presence of calcium chlorides in some soils in 2020, which are identified as evidences of secondary salinization developed by the 1990s. It is shown that the catenary method of terrain soil survey may be used in combination with satellite information and digital data processing for mapping the soil cover under post-irrigation conditions. This enables the reflection of the main soil groups, the depth of the upper saline horizon, and the presence or absence of carbonates on the soil surface. Such information is necessary for the development and selection of optimal reclamation measures. [ABSTRACT FROM AUTHOR]

The analysis of 34 cloudless fragments of Landsat 5, 7, and 8 images (1985-2014) on the territory of Plavsk, Arsen'evsk, and Chern districts of Tula oblast has been performed. It is shown that bare soil surface on the RED-NIR plots derived from the images cannot be described in the form of a sector of spectral plane as it can be done for the NDVI values. The notion of spectral neighborhood of soil line (SNSL) is suggested. It is defined as the sum of points of the RED-NIR spectral space, which are characterized by spectral characteristics of the bare soil applied for constructing soil lines. The way of the SNSL separation along the line of the lowest concentration density of points on the RED-NIR spectral space is suggested. This line separates bare soil surface from vegetating plants. The SNSL has been applied to construct soil line (SL) for each of the 34 images and to delineate bare soil surface on them. Distances from the points with averaged RED-NIR coordinates to the SL have been calculated using the method of moving window. These distances can be referred to as averaged spectral deviations (ASDs). The calculations have been performed strictly for the SNSL areas. As a result, 34 maps of ASDs have been created. These maps contain ASD values for 6036 points of a grid used in the study. Then, the integral map of normalized ASD values has been built with due account for the number of points participating in the calculation (i.e., lying in the SNSL) within the moving window. The integral map of ASD values has been compared with four traditional soil maps on the studied territory. It is shown that this integral map can be interpreted in terms of soil taxa: the areas of seven soil subtypes (soddy moderately podzolic, soddy slightly podzolic, light gray forest. gray forest, dark gray forest, podzolized chernozems, and leached chernozems) belonging to three soil types (soddy-podzolic, gray forest, and chernozemic soils) can be delineated on it. [ABSTRACT FROM AUTHOR]

A new methodological approach aimed at the creation and correction of digital soil maps on the basis of systematized and georeferenced available cartographic and attribute information arranged into a GIS project has been tested. The particular stages and methods of the creation of a digital map of salt-affected soils of Khakassia with the use of GIS technologies in the ArcInfo format are described. All the available cartographic materials, including the Soils of Russia GIS project, digital elevation models, remote sensing data, and analytical data on 82 soil pits (including the authors' materials and previously published data), have been used for the creation of this new map. [ABSTRACT FROM AUTHOR]