Abstract

The estimation of organic matter in the course of a soil study is of fundamental importance since this soil component affects markedly the physical, chemical and biological properties of the soil. Just like clay, it possesses many of the properties of colloids: it modifies greatly the readiness with which mineral plant food is rendered available to the crop and it is the medium in which the micro-organisms in the soil live and perform their functions. The loss-on-ignition method was probably the first to be employed for the estimation of soil organic matter. But this gives very unreliable results especially when the soil contains clay and carbon- ates. As a striking example could be mentioned the analysis of a sample of black soil from Hagari. This gives a loss on ignition (ex- clusive of moisture lost at 100") of about 7%. Out of this there is only 09% of organic matter, the rest of the loss being due to carbonates and combined water. Methods employing sodium hydroxide. ammonia or hydrogen peroxide are probably useful for the estimation of parti- cular parts of organic matter present in the soil and not for the whole of it. (1)

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