Identification and Mapping of Surface Carbonate Soils in the Dry-Steppe Zone of Volgograd Oblast

Abstract

Surface carbonate soils were identified and mapped in the dry steppe zone of Volgograd oblast on the territory of the Volga–Don irrigation system, stretching along the Volga–Don Canal. The study site is the Oroshaemaya experimental station in the center of the irrigation system. Field no. 28 of the station is used as an example to show all the stages of creating a digital vector map based on high-resolution space images (0.5–0.7 m) from the Pleiades satellite (April 25, 2020) and field studies in 2022–2023. Field studies included route work to determine the presence of carbonates in the surface horizon of soils (by effervescence from the interaction of soil with a 10% HCl solution). The degree (class) of soil effervescence was also assessed visually. The first stage of mapping included the classification of the space image of this field and the construction of a vector layer of the field boundary. The second stage included the creation of a vector file of the map consisting of polygons of different classes in the field (according to the prevailing degree of soil effervescence) and the calculation of the share of different classes within the vectorized polygons. Modern programs (Random Forest, QGIS) were used to classify and vectorize polygons of surface carbonate soils. The sequence of technological stages of map creation, the algorithms, and the functions used are shown. In the future, it is expected to find a relationship between the degree of soil effervescence and the amount of carbonates in the surface horizon of soils. As a result of solving this problem, space materials and a simple, fairly prompt method for field identification of surface carbonate soils will make it possible to obtain quantitative indicators of the content of carbonates in the arable horizon. The map created reflects the scale of anthropogenic impact on soils and helps to determine the necessary reclamation measures to improve their condition.