[Terrapreta] TP charcoal content and soil fertility

[Christoph Steiner]

Dear Sean and Michael,

The number 30% refers to the proportion of charcoal from total soil
organic matter content. If a Terra Preta contains 10% of carbon the
charcoal content is around 3%. The normal Oxisols have medium C contents
of around 3% in the topsoil.
I agree that Terra Preta has its own soil ecology. Once these favorable
conditions were created, we might have positive feedback loops. Charcoal
might be one additive to create this soil environment. Furthermore, Terra
Preta contains a lot of phosphorus and calcium. These minerals are very
scarce in the Amazonian environment and they were deposited as bones. I
guess this is the reason why it is possible to find snails with shells on
Terra Preta. The pH is very different on Terra Preta too. Whereas the
ordinary soils have very low pH (around 4 and sometimes even below) the
Terra Preta soils have a pH around 6. Low acidity, nutrient availability,
increased soil organic matter content, different physical properties,?
make Terra Preta quite exceptional and therefore a unique manmade
agroecosystem.
I agree that deficits of the surrounding soils make the difference to
Terra Preta especially obvious. However the fascinating thing about Terra
Preta is that its existence proofs that this infertile soils can be
transferred into fertile soils and sustainable soil organic matter
management is possible in the humid tropics!

Christoph



> Message: 1
> Date: Fri, 20 Apr 2007 01:17:40 -0500
> From: "Sean K. Barry" <sean.barry at juno.com>
> Subject: Re: [Terrapreta] Charcoal  mix continued
> To: <terrapreta at bioenergylists.org>,	"Michael N Trevor"
> <mtrevor at ntamar.net>
> Message-ID: <AABDCSYZHAPR5YRA at smtp01.nyc.untd.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
>
> Michael,
>
>
> Christoph Steiner mentioned, on reading the comment about 30% density of
> charcoal in Terra Preta soil that he thought that number was high (maybe
> even quite high).  I have never actually measured charcoal content in any
> soil, let alone Amazon Terra Preta soil.  He has.  I think we should take
> heed of his first hand experience with the actual Terra Preta soil in the
> actual places where it was discovered.  By his reference, I would
> consider it a given that charcoal is not nearly as dense as 30% in any
> known Terra Preta soils.  I do think Christoph would agree that the
> charcoal found in some examples of Terra Preta soil exists in quite deep
> layers (up to 5 feet?) and that it probably was laid down in those areas
> slowly over quite a long period of time.
>
> I do not believe, either, that density of charcoal alone is a defining
> issue as to what makes Terra Preta soil a much better plant growing
> medium than surrounding soils.  I think, rather, that Terra Preta soil is
> an ecology of soil, a habitat in the soil, that promotes improved health
> of soil microorganisms.  The improved soil microbiological activity then
> improves the soil habitat for plants which grow above the soil and root
> into it.
>
> The significant improvement of food crops grown in Terra Preta soils
> versus surrounding oxisol native soils in the Amazon rainforest, may also
> be related to the substantial defiicit that those native soils present
> for food crops.  Even a normal bloom in a desert would be measured as
> outstanding one by anyone familiar with what can and does normally grow
> in a desert.
>
> SKB
> ----- Original Message -----
> From: Michael N Trevor<mailto:mtrevor at ntamar.net>
> To: terrapreta at bioenergylists.org<mailto:terrapreta at bioenergylists.org>
> Sent: Wednesday, April 18, 2007 9:38 PM
> Subject: Re: [Terrapreta] Charcoal mix continued
>
>
>
> Dear Sean
>
>
> Thanks for the addition feed back and information. So in human terms
> charcoal addition is partially permanent, being long term and persistent.
> I like your comment, its presence being like a catalyst in as what ever
> it does it seems to remain.. If it has built up to 30% in some places over
> thousands of years then the actually beneficial amount needed in short
> term must actually be pretty small. If my reasoning is not wrong and we
> get 30 % for 3000 years, then doses like 10 and 20 percent should be
> pretty high up on the scale since even amounts like.03 percent per year
> might have accumulative effects over time.
>
> Regards,
>
>
> Michael
>