Measurement of Soil Organic Carbon Pools Isolated Using Bio-Physical-Chemical Fractionation Methods

Abstract

The studies were performed with samples from different horizons of soddy podzolic soil (Albic Retisol) and typical chernozem (Haplic Chernozems) collected under natural lands and arable fields. The carbon contents in structural (particulate organic matter of 2-0.05 mm in size (CPOM) and mineral-associated organic matter of 0.05 mm in size (CMAOM)) and process (potentially mineralizable organic matter (C0) and microbial biomass (Cmic)) pools were determined. In the humus horizon of virgin and arable sod-podzolic soils, the CPOM, CMAOM, C0, and Cmic pools contained 38 and 24, 56 and 72, 5.9 and 5.6, 1.2 and 1.3% of Corg, respectively. The sizes of these pools in virgin and arable chernozem were 42 and 30, 53 and 68, 3.6 and 2.8, 0.5 and 0.5% of Corg, respectively. The emission potential of CPOM pool despite the small mass of the POM fraction was comparable to CMAOM pool having the large MAOM fraction. A method for quantitative separation of soil organic matter (SOM) into active, intermediate (slow), and passive pools has been proposed. The size of the SOM active pool were determined based on the Сmic and C0 contents, and the size of the passive pool were measured by the chemically non-oxidizable organic matter in POM and MAOM fractions. The intermediate pool size was calculated by the difference between the total organic carbon and the sum of the active and passive pools. The active, intermediate and passive pools of the studied soils contained 1–7, 51–81 and 13–48% of Сorg, respectively without any significant between different land uses.