Identification of Surface-Carbonate Soils and Soils with Variegated Underlying Rocks Using Classification of Space Image, the South of Volga Upland

The aim of the work is to reveal the correlations between the spectral characteristics of the open soil surface in the Pleiades image (04/25/2020) and soils in a key plot with a complex soil cover pattern in the southern part of the Volga upland (Volga-Don irrigation system, Volgograd oblast). The territory is characterized by high lithological heterogeneity: Paleogene and Neogene sands and loams are overlain by a cover of Quaternary brown loams of variable thickness from 1–2 m to complete wedging. The soil cover is represented by light chestnut solonetzic complexes complicated by a mosaic of lithological variants and erosion-accumulative combinations. Basing on digital methods of processing the spectral characteristics of the satellite image and the use of ground-based soil information, eight soil groups were separated and a map of their distribution was created for a key plot of 343 ha. Soil groups differ in general features of the soil surface due to the presence and amount of rubble and stones, the texture of the surface horizon (from sand to medium loam), the presence of brightened crusts on the surface, the presence or absence of HCl effervescence from the surface, depending on the thickness of the first lithological layer. Within individual groups, soils with different profile structures (agro chestnut, agrozems, agrosolonetzes) are combined. Soils of the same type and sometimes subtype fall into different groups according to spectral characteristics. This is due to the incomplete correspondence of the properties of the soil surface, which affect the spectral characteristics, and the internal structure of the soil profile as a whole.