Estimation of soil saturation with organic carbon

New definitions of “soil carbon sequestration” and “soil carbon deposition” on a quantitative basis taking into account the period of the complete turnover of accumulated organic matter and its distribution over the soil profile are formulated. The carbon protection capacity of soils in the European part of Russia was determined according to Hassink (1997) and Six et al. (2002) based on data of the fine fractions content and the mineralogical composition of soils. The carbon saturation degree of soils and their carbon sequestration potential were calculated according to Meyer et al. (2017) and Wiesmeier et al. (2014). Gray forest and chestnut soils were classified as poorly saturated with organic carbon, meadow slitized and floodplain meadow soils were moderately saturated, and chernozems was saturated. It has been shown that the carbon sequestration potential of gray forest soil is about 30 t C ha-1, chestnut soil does not exceed 25 t C ha-1, meadow soil is 15-20 t C ha-1, and chernozem is less than 5 t C ha-1. Critical remarks to the 4 ppm initiativewere given.