This method semi quantifies the amount of oxidizable organic matter in soil based on gravimetric weight change associated with high temperature oxidation of organic matter. After initial oven drying at 105°C, the samples are ignited in a muffle furnace for 2 hours at 360°C. 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.
Western Region Method S - 9.20, Soil Organic Matter – Loss On Ignition Method. Soil, Plant and Water Reference Methods for the Western Region – 4th Edition, Miller, R. O., Gavlak, R. and Horneck, D., 2013, pp. 77-78.