The Assessment of Soil Organic Carbon Pools in Different Soils Using Four Fractionation Methods

ABSTRACT

The sensitivity of SOC (soil organic carbon) fractions can provide information on soil organic matter proxies and kinetically defined components related to their chemical composition and oxidability. The purpose of this study was to assess the stability of SOC on five soil types (Arenosols, Chernozems, Fluvisols, Vertisols and Solonetz) and three land uses (cropland, meadow and forest). To obtain SOC functional fractions chemical, physical and density fractionating methods were used as follows: SOC susceptible to oxidation with 333 mM KMnO₄ (SOC_KMnO4S), SOC with varying degrees of oxidation resistance by the modified Walkley-Black method (SOC_wb1, SOC_wb2, SOC_wb3, SOC_wb4), particulate SOC (SOC_par); mineral-associated SOC (SOC_mas), aggregate-associated size classes of the SOC (SOC >2000, SOC2000–250, SOC250–53, SOC <53). The relative contribution of fractions in SOC was as follows: SOC_KMnO4S (7.9–42.5%), SOC_wb1 (35.6%) > SOC_wb2 (27.5%) > SOC_wb4 (22.7%) > SOC_wb3 (14.2%), SOC_mas (56.6–76.4%) > SOC_par (23.6–43.4%), SOC >2000 (8.2–44.8), SOC 2000–250 (27.4–34.9), SOC 250–53 (13.4–27.4%), SOC <53 (5.4–28.8%). Fractions SOC_par, SOC_wb4, SOC >2000 and SOC <53 showed sensitivity to land use, whereas SOC_mas, SOC _KMnO4S, SOC_wb3 showed variations among soil types. The fraction SOCwb1 indicated sensitivity to both land use and soil type. Considering obtained functional fractions of SOC it was possible to determine discriminators between particular soil types or indicators of land use changes due the anthropogenization.

KEYWORDS:

• Carbon fractions
• fractionating methods
• land
• soil organic carbon
• soil type

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported from the Ministry of Education, Science and Technological Development with grant Nr. 451-03-47/2023-01/200117.