Cobalt content in agrocenoses soils of the Omsk Irtysh region

The aim of this study was to establish distribution patterns and assess the content of acid-soluble and mobile cobalt compounds in different soil types in agrocenoses of the Omsk Irtysh region. From 2009 to 2019, soil pits were established, with samples collected from the genetic soil horizons of agricultural landscapes in the forest-steppe and steppe zones of the Omsk region. In the southern taiga and northern forest-steppe soils, samples were collected from the 0–20 cm layer. The average acid-soluble cobalt content, close to the total content, in the arable horizons of agrochernozems, quasi-gleyic agrochernozems, solonetzes, and agrosolonetzes was 11.3, 12.4, and 13.3 mg/kg, respectively. Concentrations of mobile forms of the microelement (1H acetate-ammonium buffer) in them were similar: 0.11–0.12 mg/kg. Their share of the total element content was 2.3% in agrochernozems, 1.4% in quasi-gleyic agrochernozems, 0.9% in solonetz and agrosolonetz. The content of mobile cobalt (1H HNO3) in agrosod-podzolic soils was 0.38-1.10 mg/kg, in agrogray forest soils – 0.50–1.45 mg/kg, in clay-illuvial agrochernozems - 0.85-1.25 mg/kg. Concentrations of the mobile form of the microelement in all soils are assessed as low and medium. The content of acid-soluble cobalt in soils was influenced by the content of physical clay (r = 0.61), silt (r = 0.49), total iron (r = 0.60), the value of cation exchange capacity (r = 0.52). The concentration of the mobile form was influenced by the content of silt (r = 0.44) and the amount of acid-soluble cobalt (r = 0.41). The content of mobile cobalt in agrosod-podzolic, agro-gray forest soils and clay-illuvial chernozems depended on the pH value (r = 0.65). When cultivating agricultural crops on the soils of the Omsk Irtysh region, it is likely be needed to use cobalt-containing microfertilizers.