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A laboratory method of burning off organic matter within a soil sample to determine the soil organic matter content. An air-dried soil sample placed in a furnace and typically heated to 500C for 4-hours, or longer. The difference in mass between the original sample and the residue is the percentage content of organic matter that has been oxidised.

The formula used for calculating the percentage loss is

(Original air-dried mass (g)-mass after heating in furnace (g) )/(Original air-dried mass (g)) x 100% = Organic matter %

A worked example where 7g is lost during burning of the sample, and which had an original mass of 110g is: (110-103)/110 x 100% = 6.36% OM.