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415

Organic Matter - Loss-On-Ignition Method

PHYSIO CHEM:  OM (LOI), Org.C (LOI)

Summary

This method estimates soil organic matter based on gravimetric weight change associated with high temperature oxidation of organic matter.  After initial oven drying at 105ºC, the samples are ignited in a muffle furnace for 2 hours at 360ºC.  The percent weight loss during the ignition step is reported as OM-LOI (% wt. loss) with a method detection limit of 0.05 %.  The calculation of organic carbon is based on the assumption that organic matter contains 58% carbon. 

Note:  To improve the accuracy of estimation of organic matter from loss-on-ignition data, it is recommended that a comparison study of OM by Walkley-Black and LOI be performed to determine the relationship between the two measurements.  The resulting equation can then be used for better estimation of organic matter from LOI values for similar samples.

Sample amount requested:  50 g
Questions concerning limited sample size can be answered by the UC Davis Analytical Laboratory.

Nelson, D. W., and Sommers, L. E. 1996. Chapter 34. p 1001-1006. Total Carbon, Organic Carbon, and Organic Matter. In: J. M. Bigham et al. (ed.) Soil Science Society of America and American Society of Agronomy. Methods of Soil Analysis. Part 3. Chemical Methods-SSSA Book Series no. 5. Madison, WI.