The characterization, genesis and classification of six selected soil profiles of the Kursk Oblast, Russia

Chernozem soils are perhaps one of the most interesting soils in the world; certainly they are well known and worthy of investigation. Chernozemic soils are a very important resource to Russia. Understanding soil properties is essential in maximizing the use and protection of this resource. Creating natural soil standards, with chemical characterization, is critical in delineating the effects of pollution in the soil ecosystem, evaluating risk assessment and devising management schemes. Another aspect of chernozems is the unique genesis dilemma they present. The number of loess depositions, weathering periods and the variability in depth to the underlying geology is not well understood. Soil classification is an integral part of soil science that provides a means to organize knowledge, communicate effectively between researchers and the general public, and aid in research design. The classification of the soils using both U.S. and Russian systems is important to understand key properties of each of the six soil profiles, and also to understand the similarities and differences between the two systems.

Six chernozem soils were selected, sampled and described on the V.V. Alekhin Central-Chernozem Biosphere Reserve, in the Kursk Oblast, Russia. The sites are representative of the Kursk region. Two parent material sequences are present in the study area: loess over Tertiary sands or loess over Cretaceous chalks. Laboratory analyses performed on all sites included pH, cation exchange capacity, exchangeable bases, dry combustion of C, N, and S, total element dissolution analysis, KCI extractable aluminum, particle size, dithionate iron, hydroxylamine easily reducible manganese, Walkley-Black organic carbon, and neutralization potential.

The objectives of this study were to evaluate three soil profiles near Kursk, Russia, for physical characterization, genesis interpretation and classification. Chemical characterization revealed a CEO range of 14-39 cmol⁺ kg^-1 with approximately 100% base saturation that is dominated by calcium. The soils studied all have a high buffering capacity and low concentrations of potentially toxic elements. Phosphorous was the only potentially deficient nutrient with approximately 500 to <50 mg kg^-1 total P. These soils should make excellent reference standards for future risk assessment of Kursk chernozems.

In regard to genesis, different loess depositions were not evident. Loess appears to be thickest over the Cretaceous Chalk geology. The soils were high in organic carbon and nitrogen and a slight decrease in these compounds was observed in the slightly disturbed soils.

The soils were classified as Pachic Paleudolls, Pachic Hapludolls or Cumulic Hapludolls according to U.S. soil taxonomy. Using Russian soil taxonomy all soils were post lithogenic, humus accumulative soils and considered saturated, leached, segregationary chernozems at the subtype level.