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United States Department of Agriculture

Agricultural Research Service

Title: Development of Rapid Instrumental Methods for Measuring Soil Organic Carbon

Authors
item MCCARTY, GREGORY
item Reeves Iii, James

Submitted to: Advances in Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 15, 2000
Publication Date: N/A

Interpretive Summary: Evidence for global climate change has intensified international efforts toward reducing anthropogenic carbon dioxide sources and increasing sink capacities of the terrestrial biosphere. With agricultural ecosystems comprising an important part of the terrestrial biosphere, assessment of sink/source relationships within these ecosystems is essential for assessing sink capacity of the global biosphere. Within a market-based system for regulating carbon dioxide emissions, agricultural production systems could earn credits and make substantial contributions towards meeting net emission goals but better methods are needed for measuring soil organic carbon. This work evaluates the use of near infrared reflectance spectroscopy (NIRS) and analytical pyrolysis as instrumental methods for rapid characterization of soil organic C. The results obtained showed that NIRS holds good promise as a method for rapidly measuring the amount of soil organic C. In addition, pyrolysis can rapidly assess changes in composition of soil organic matter under different agricultural management. Characterization of soil ecosystems by these techniques can permit better assessment of C sequestration in ecosystems.

Technical Abstract: The extensive spatial structure of organic C in natural and agricultural ecosystems usually constrains the accuracy of C storage assessments for landscapes. A complex spatial structure will often lead to higher error associated with under-sampling the landscape compared with the analytical error associated with measurements. Tradeoffs may be necessary between the eanalytical accuracy and the speed and ease of analysis in order to increas sample handling capacity. Near infrared reflectance spectroscopy (NIRS) offers a simple and rapid procedure for measurement of soil organic C with some possible loss in accuracy for the individual analyses when compared to standard chemical methods. The feasibility of using NIRS for assessing spatial structure of soil C on a landscape is being evaluated by using within-field calibrations for organic C. The results have indicated that NIRS has good utility for assessing C storage in agricultural ecosystems. Pyrolysis-GC/MS is another instrumental method with good utility for rapid assessment of composition of complex organic matrices such as soil organic matter. This method provides a clear signature for lignin which is an important precursor for stabilized soil organic C. Initial studies indicate that some soil ecosystems that have been characterized with high capacity to store C also carry a strong lignin signature detected by pyrolysis. Characterization of soil ecosystems by these techniques may permit assessment of C sequestration in ecosystems.

Last Modified: 7/28/2014
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