The geography of Vertisols and Vertic soils in the Kuban-Azov Lowland

Abstract

The soils shown on Russian soil maps of the Kuban-Azov Lowland under the names of slitic (vertic) and compacted soils contain diagnostic features characteristic of the type of dark slitozems and subtypes of slitic soils in the new Russian soil classification system, or Vertisols and Vertic soils in the WRB system. These are slickensides, wedge-shaped structure, clayey texture through the entire soil profile, and shrinkage cracks formed during soil drying. It was found that dark quasi-gley slitozems (Vertisols) occur in the central parts of the bottoms of large (> 1.5 km along the longest axis) closed depressions. Humus quasi-gley slitozems (Vertic Stagnic Phaeozems (Clayic, Pachic)) are confined to the peripheral parts of the bottoms of these depressions and to the bottoms of smaller (0.8–1.5 km) closed depressions. Deeply slitic humus—quasi-gley soils and deeply slitic clay-illuvial chernozems (Bathyvertic Stagnic Phaeozems (Clayic, Pachic)), in which the upper boundary of slickensides is found at the depths from 100 to 200 cm, usually occur in the bottoms of closed depressions with the longest axis of less than 0.6–0.8 km and in the bottoms and on slopes of shallow flat-bottomed ravines. With respect to the distribution of Vertisols and Vertic soils, the Kuban-Azov Lowland can be subdivided into eight soil districts. In five of them, these soils occupy from 0.1% to 12.1% of the territory.