Soil Organic Matter Testing: An Overview

Abstract

Soil organic matter is one of the most important properties affecting chemical reactions and the availability of nutrient elements to plants. Organic matter is the most complex, dynamic, and reactive soil component. Organic carbon (C) can be determined from the difference between total C and inorganic C. The use of external heat to complete the oxidation of organic C by the dichromate–sulfuric acid procedure and a reflux condenser to minimize loss of CrO2Cl2 produced from the reaction of K2Cr207 and Cl2 in some soils, especially saline soils, was introduced by L. J. Mebius. The wet combustion methods involving dichromate for determination of organic C in soils, have been modified to use colorimetric analysis instead of titration. Automated instruments are commercially available that can be used for determination of total C in soils, but a correction must be made for inorganic C present in calcareous soils.