Decomposition | Forms and Function | Management of Soil Organic Matter | Carbon Cycle
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An output of the ‘Soil Health for Sustainable and Productive Landscapes’ Project
Active carbon is an indicator of the fraction of soil organic matter that is readily available as a carbon and energy source for the soil microbial community (i.e., food for the soil food web). The soil is mixed with potassium permanganate (deep purple in colour) and as it oxidizes the active carbon the colour changes (becomes less purple), which can be observed visually, but is very accurately measured with a spectrophotometer.
|How active C relates to soil Research has shown that active carbon is highly correlated with and similar to “particulate organic matter, which is determined with a more complex and labour intensive wet-sieving and/or chemical extraction procedure. |
Active carbon is positively correlated with percent organic matter, aggregate stability, and with measures of biological activity such as soil respiration rate. Research has shown that active carbon is a good “leading indicator” of soil health response to changes in crop and soil management, usually responding to management much sooner (often, years sooner) than total organic matter percent. Thus, monitoring the changes in active carbon can be particularly useful to farmers who are changing practices to try to build up soil organic matter (e.g., reducing tillage, using new cover crops, and adding new composts).
Figure 1. Sample tubes containing potassium permanganate solution