[Terrapreta] Soil Food Web

[Sean K. Barry]

Hi Larry,

You say:
when charcoal with it's pore spaces are occupied with microbes and when charcoal, consisting of carbon binding sites for nutrient ions, is used then the structure, charcoal, hosts the functions of microbes, fungi, roots and nutrients.

I like yours and Tony's comments on structure.  The corral reef is an apt analogy to biochar in soil.  It is just a physical thing, though.  There is NO chemical use by organisms on coral reefs of the calcium carbonate in coral reefs.  If there was, then the reef would disappear.  I don't think that charcoal itself interacts chemically with microbes or the nutrient ions in soils, either.  The charcoal has physical impacts on the soil structure (greatly increased "enclosed" surface area I suspect is the greatest addition), but it is not chemically active, per se.

CEC in soil is generally increased by the addition of soil organic matter and by some clays which both do have more "binding sites" for cations of nutrients like Calcium and Potassium, etc.  The number of "binding sites" (negatively charge sites attracting positively charged cations) is measured in Million equivalents per gram Meq/g, meaning the number of millions of negative charges per gram of the soil.  Charcoal carbon does not have high numbers of negative charges on its surface and so does not increase CEC directly when it is added to soils.

Charcoal carbon, when added to soil does appear to increase the growth in populations of soil microbes and the activity of soil microbes in the soil, leading to an increase in soil organic matter, and hence an increase in CEC.

Regards,

SKB
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