Permanganate-Oxidizable Carbon in Humus Horizons of Soils in the European Territory of Russia

The paper provides a detailed analysis of the soil permanganate-oxidized carbon (POХС) method. The purpose of this work was to describe the range of POXC values in the humus horizons of soils of different land uses of the European territory of Russia and to assess the possibility of using it as an indicator of the state of soil organic matter. The work objectives included: a) the selection of the corresponding soil mass for the analysis; and b) determination of the range of POXC values in soddy-podzolic soils (Retisols), gray soils (Greyzemic Phaeozems), and chernozems (Haplic Chernozems) of different land uses of the European territory of Russia. For soils with the carbon content from 1.6 to 4.7% a negative nonlinear relationship between the POXC values and the sample mass was established: with an increase in the sample mass in the range of 0.5–7.0 g, the average POXC decreases by 1.5–3.0 times for both natural and agricultural soils. The most suitable mass for determining POXC is 2.5 g, since it allows determining POXС for soils with the greatest variation in the total carbon content. The absolute values of POХС for three types of soils in the European Russia were from 358 to 1040 mg/kg, relative content varies from 1.2 to 4.4%. The considered permanganate-oxidizable carbon method makes it possible to assess the pool of TOC, probably most easily metabolized by soil microbiota. Low analytical variability, sensitivity of the observed values of permanganate-oxidizable carbon (POC) to soil type and land use allows us to consider this parameter as a promising indicator of soil health assessment.