Genetic Features of Soils on Hard Rocks of the Donetsk Ridge

Morphological, physical, and chemical properties of Chernozems on hard parent rocks are analyzed in this work. The research was performed on virgin soils of protected areas in the northwest of Rostov oblast. This area is located on the eastern slopes of the Donetsk Ridge with frequent outcrops of hard rocks. It has been found that morphological, physical, and chemical properties of Chernozems on hard rocks make them unique and at the same time enable us to assign them to the order of Chernozems. In comparison with the zonal soil—ordinary and southern chernozems (Calcic Chernozems),those on hard rocks are characterized by a smaller thickness of humus-accumulative layers, an increased humus content, presence of gravel in the lower part of the profile, weakly pronounced carbonate pedofeatures, and particularities of particle-size soil components patterns even within one texture variety. Secondary carbonates (pseudomycelia and nodules) in chernozems on dense carbonate rocks are absent or are indistinctly pronounced. This is their distinction from similar soils of the same order of Chrernozems on fine-grained rocks (Calcic Chernozems), for which the kind of secondary carbonates is a diagnostic criterion. Therefore, the assignment of these soils to the subtype level in the soil classification of the USSR is incorrect. Dark-humus soils, which often occur on the spurs of the Donetsk Ridge, were previously classified as incompletely formed chernozems, they differed from chernozems by the absence of the middle-profile horizon and of carbonate pedofeatures.