Potential for Quantification of Biologically Active Soil Carbon with Potassium Permanganate

Oxidation of soils with 333 mM potassium permanganate (KMnO4) has been identified as a means to quantify labile soil carbon (C) and may have potential for rapid measurement of biologically active soil C. In the current study, active C pools in several soils were estimated by oxidation with a range of KMnO4 concentrations and compared to estimates determined from carbon dioxide evolution during 28-d incubations. Digestion with 333 mM KMnO4 identified larger active C pools than did incubation data. However, shaking soils for 15 min with 2.5 mM KMnO4 provided estimates of active C that accounted for 1.5 to 1.9% of the total C pools and were not significantly different than those estimated using incubation data. Oxidation with dilute KMnO4 appears to be feasible to rapidly quantify active soil C pools. However, measurements are dependent on KMnO4 concentration and shaking time, so great care is needed to assure consistent results.