Is the Walkley–Black Method Suitable for Organic Carbon Determination in Chilean Volcanic Soils?

Although dry combustion (DC) carbon dioxide (CO2) is an accurate method to measure total soil carbon (C), it is a rather expensive one. Therefore, wet oxidation by the Walkley–Black (WB) method is widely used in acidic Chilean volcanic soils, although there are no studies comparing both WB and DC. The aim of this article was to compare DC and WB in a range of volcanic soils containing between 2% and 9% of soil C on a regional scale. Results indicated that the recovery (R) of soil C by WB with respect to DC varied between 70% and 82%. Consequently, the correction factor (100 / R) ranged between 1.26 and 1.47. The standardized major axis regression analysis indicated that the slope and the intercept of the fitted line on volcanic soils were similar to 1:1 line. In conclusion, WB was an economically suitable method to determine the soil C content of Chilean volcanic soils.