[Terrapreta] Old native earth ovens.

[Kevin Chisholm]

Dear Sean

Sean K. Barry wrote:
> ...del...
>  
> The Terra Preta found in the Amazon River basin was on a very large 
> scale.  They had to actively and continuously be producing charcoal 
> for many many years, perhaps centuries to have covered the area and 
> the depths they covered with TP soils there, I think. 

Has anyone ever counted up teh number of known Terra Preta Sites and 
determined their average area, to be able to estimate the actual area of 
Brazil that is covered by man-made Terra Preta?

Black Earth Soils occur naturally in nature. I have heard figures like 
"The area of Terra Preta in Brazil is about the same area as France." 
What percentage of teh Black Earth Soils in Brazil are naturally made 
and what percentage of tehm are actually man-made?


> What these Tolais people may have been similar, but I suspect making 
> Amazon style TP soils would take quite a long time.  Its just a 
> thought though.  Maybe the effect could be made to happen overnight or 
> in a single growing season with one application of the "right stuff", 
> too.  Who knows?

What would be the necessary features of a Black Earth Soil that would 
differentiate it from a man-made Terra Preta Soil?
>  
> One time some one mentioned that the only hard stone like anything 
> that can be found in the Amazon River basin is fired clay.  And, fired 
> clay does not wash way like the clay mud does.  I'm thinking that 
> keeping precious charcoal and garden soil from washing away in the 
> almost daily rains of the Amazon rainforest was pretty important.  
> They built dike and swales, too, it seems.  So, I kind of thought that 
> the fired clay in the TP soils was there just to keep it from washing 
> away.

Is the presence of fired clay a necessary feature of a soil, for it to 
be termed a "Terra Preta Soil?"

Thanks.

Kevin
>  
> Regards,
>  
> SKB
>