Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/16/2011
Publication Date: 3/1/2012
Citation: Culman, S.W., Snapp, S.S., Freeman, M.A., Schipanski, M.E., Beniston, J., Lal, R., Drinkwater, L.E., Franzluebbers, A.J., Glover, J.D., Grandy, A.S., Lee, J., Six, J., Maul, J.E., Mirsky, S.B., Spargo, J.T., Wander, M.M. 2012. Permanganate oxidizable carbon reflects a processed soil fraction that is sensitive to management. Soil Science Society of America Journal. 76:494-504. Interpretive Summary: Soil quality is an essential feature of sustainable agricultural systems, as many important ecosystem services (e.g. nutrient cycling, water cycling, climate regulation, etc.) are functionally derived from well-working soil properties and processes. The biological component of soil quality has been difficult to assess due to its highly dynamic nature and diversity of processes controlled by soil microorganisms. A group of scientists from Michigan State University, Pennsylvania State University, Ohio State University, Cornell University, University of New Hampshire, University of California, University of Illinois, US Agency for International Development, and USDA Agricultural Research Service in Beltsville Maryland and Watkinsville Georgia collected soils from 12 studies at 53 sites to evaluate the potential of using a simple, rapid, biochemical method (permanganate oxidizable carbon) as a biological soil quality tool. The biological soil quality tool was highly related to other more process-oriented and methodologically-sophisticated biological evaluation measures. In fact, this simple biological soil quality tool was sometimes more effective in discriminating among different soil treatments. Our rigorous and widespread evaluation across a diversity of soils suggests that this simple, rapid, and inexpensive biochemical method can be widely used to evaluate management-induced changes in biological soil quality. This has important implications for assessing the impacts of land restoration and management for maintaining and improving ecosystem services derived from the world’s soils.
Technical Abstract: Permanganate oxidizable C (POXC; i.e., active C) is a relatively new method that can quantify labile soil C rapidly and inexpensively. Despite limited reports of positive correlations with particulate organic carbon (POC), microbial biomass carbon (MBC) and other soil carbon (C) fractions, little is known about what soil fractions POXC most closely reflects. We measured POXC across a wide range of soil types, ecosystems, and geographic areas (12 studies, 53 total sites, n = 1379) to: i) determine the relationship between POXC and POC, MBC and soil organic C (SOC) fractions, and ii) determine the relative sensitivity of POXC as a labile soil C metric across a range of environmental and management gradients. POXC was significantly related to POC, MBC and SOC, and these relationships were strongest when data were analyzed by individual studies. POXC was more closely related to smaller-sized (0.053-0.25 mm) than larger POC fractions (0.25-2 mm), and more closely related to heavier (>1.7 g/cc) than lighter POC fractions, indicating that it reflects a relatively processed pool of labile soil C. Compared to POC, MBC or SOC, POXC demonstrated greater sensitivity to changes in management or environmental variation in 42% of the significant experimental factors examined across the 12 studies. Our analysis demonstrates the usefulness of POXC in quickly and inexpensively assessing changes in the active soil C pool.