Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/3/2007
Publication Date: 5/20/2009
Citation: Dell, C.J. 2009. Potential for quantification of biologically active soil carbon with potassium permanganate. Communications in Soil Science and Plant Analysis. 40(9-10):1604-1609. Interpretive Summary: Describing the cycling of organic C in soil often requires a knowledge of how C is partitioned among pools with varying retention times. The pool with the most rapid turnover is referred to as the active C pool, and its size is generally determined by the measurement of carbon dioxide evolved from soil during laboratory incubations. The incubations require several weeks, multiple carbon dioxide measurements, and can be complicated by carbon dioxide leaks. Therefore, a rapid alternative is desirable. Oxidation of soil with potassium permanganate has been used to measure labile C, but the concentration of potassium permanganate used previously identifies a large portion of the slowly degraded C, in addition to the active C pool. However, the problem can potentially be avoided by using weaker potassium permanganate solutions. In this study, the sizes of active C pools were determined using dilute potassium permanganate and incubations. Shaking soils for 15 min with 2.5 mM potassium permanganate provided estimates of active C that were not significantly different from those estimated using incubation data. However, measurements are highly influenced by potassium permanganate concentration and shaking time. Therefore, the potassium permanganate method has a large potential for measurement errors and great care is needed to ensure reproducible results. In most cases, the simplicity of incubations probably outweighs the time savings offered by the use of potassium permanganate.
Technical Abstract: Abstract Carbon dioxide evolution during laboratory incubation is frequently measured to estimate quantities of biologically-active soil C, but the time required and possible carbon dioxide leaks makes a rapid substitute attractive. Active soil C pools were measured using both dilute potassium permanganate and 28 d incubations. Shaking soils for 15 min with 2.5 mM potassium permanganate provided estimates of active C (1.5 to 1.9% of total C) which were not significantly different from those estimated using incubation data. However measurements are highly dependent on potassium permanganate concentration and shaking time, leading to a large potential for measurement errors and the need for extensive quality control. In most cases, the simplicity of incubations probably outweighs the time savings offered by the use of potassium permanganate.