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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #103773
Title: FILTER, INOCULUM, AND TIME EFFECTS ON MEASUREMENTS OF BIODEGRADABLE DISSOLVED ORGANIC CARBON IN SOIL

Author
item Schnabel, Ronald
item Dell, Curtis
item SHAFFER, JOHN - PENN STATE UNIVERSITY

Submitted to: Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2001
Publication Date: 6/20/2002
Citation: Schnabel, R.R., Dell, C.J., Shaffer, J.A. 2002. Filter, inoculum, and time effects on measurements of biodegradable dissolved organic carbon in soil. Soil Biology and Biochemistry. 34:737-739.

Interpretive Summary: The decomposition of organic carbon provides the energy for processes that cycle nutrients and other biogeochemicals in soil. Over the last decade, tests have been developed to estimate the amount of organic carbon in streams and wastewater that is quickly decomposed. These tests are now being applied in soils to estimate the availability of organic carbon to soil microbes that remove nitrate from ground water and cycle carbon through the soil. We need to clearly understand how differences among the tests affect the outcome before we can choose the most appropriate test or compare results from different tests. We determined and compared the amount of degradable dissolved organic carbon in soil by using the different tests. We found that it did matter which test was run. Contrary to what we expected, we measured more available carbon during short tests than during long tests. We concluded that this was a flaw in the longer tests and that shorter tests gave more useful results. Before these tests can be widely used, more research is needed to determine why results are so variable for individual tests and why they differ among tests.

Technical Abstract: The biodegradation of organic carbon provides the energy for processes that cycle many biogeochemicals. During the last decade, incubations of dissolved organic carbon have become popular tests for determining the amount of organic carbon that is readily biodegradable. These tests differ in length of incubation, filtration prior to incubation, and method of inoculation. We compared biodegradable dissolved organic carbon in soil b varying common experimental factors. Dissolved organic carbon (DOC) decreased to a minimum with all combinations, then consistently increased at the later stages of the incubation. The time course of DOC during our incubations resulted from a balance between microbial cycling and sorption to particle surfaces. Biodegradable dissolved organic carbon calculations were thus affected by the length of the incubation and by the combination of filters used before and after incubation. Inoculation was unnecessary, provided that filtration prior to incubation allowed bacteria to pass (2.0 um).