It is still a standard, however some reports that Walkley–Black method systematically underestimates SOC due to incomplete oxidation. Contrarily others say that this method overrates SOC because of the oxidization of inorganic (iron manganese etc.) compounds. Are these results applicable or comparable to those gained by C-N analyzers?
One of the questionable points of the method is the extent of the oxidation by dichromate. In the early variations of the method (Walkley and Black 1934; Walkley 1947), the soil samples were not heated during the oxidation step and the mean recovery of OC was found to be about 76%. Therefore it was proposed to introduce a correction factor of 1.32 for the quantification of the OC content in the soil samples (Walkley and Black 1934). Afterwards it was proposed to apply extensive heating of the sample during oxidation (Mebius et al. 1960; Heanes et al. 1984) to overcome the concern of incomplete digestion of the organic matter. In that case, no correction factor was required. However, the temperature of the oxidation must be strictly controlled due to the possible decomposition of acidic dichromate above 150◦ C. This complicates
appreciably the procedure and does not always lead to satisfactory results (Ayub and
Boyd 1994).,...Excerpts from PDFs enclosed below...
Thanks for your reply.
My real question is if I can compare my measured results to those published in the very recent literature. Methods generally say nothing about these very important details.
Please go through these PDFs , you will find , what you intend to find out..
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