[Terrapreta] Charcoal mix continued

[Juergen Botz]

Michael N Trevor wrote:
> One thought, at the risk of repeating what may have been said before, if
> Amazonian terra preta
> soils are about 30% charcoal, what was the percentage when they were taken
> out of useage?
> Does the percentage of charcoal reamin fairly constant once incorporated
> into the soil?

Once incorporated, sure... where would it go?  But you seem to be assuming
that it was explicitly incorporated by human action.  I doubt that very 
much... I don't think the Indians plowed the charcoal into the soil.  They
probably just added a layer to the top each year.

> Also since these soils were apparently developed over hundreds and even
> thousands of years
> even minute amounts must be beneficial. It would seem likely that producing
> and incorporating charcoal
> in to the soil would have occured in rather small sequential doses over
> generations. Massive charcoal generation
> to jump to a high percentage would seem unlikely unless it was carried out
> small plot by small plot.

Layer by layer.  Each year, or every few years, a thin layer of charcoal, 
followed by a layer of fallen leaves and other plant detritus, followed
eventually by a layer of sediment from periodic flooding.  After a 
few hundred years of that you have a couple of meters of rich soil
containing 1/3 charcoal.  Under that is the original oxisol.

:j