[Terrapreta] more on logistics of corn biochar

[Robert Klein]

I share here a couple of posts by Sean and Gerry from
the terra preta list and my responses.  These help to
refine aspects of the corn stover hypothesis.

Hi Robert,
 
#2? What nutrients does the ash provide?  The soil is
already very alkaline and white ash from complete
combustion of any biomass is very alkaline.  I do not
believe either, that ash is a reasonable substitute
for plant nutrients like Nitrogen-N, Phosphorus-P,
Potassium-K, Sulfur-S, Calcium-Ca, Iron-Fe,
Magnesium-Mg, etc.

>Burning is used in all primitive agriculture through
the method of ‘slash and burn’ to release nutrients
captured by the biomass back unto the surface.  It is
in the form of ash and this means that most of it is
very soluble and easily leached away.  Biochar would
likely be much more retentive as the evidence
suggests.
 
Charcoal in the original Terra Preta is in large
chunks.  Larger chunks than will come from corn stover
(almost power).

>Charcoal from wood will leave chunks that will take
centuries to break down, which is why it is not nearly
as suitable for the creation of these soils unless
they are finely crushed.  Plant waste such as stover
is already finely divided after charring and is easily
incorporated into the soils which have been shown to
hold several per cent of carbon.
 
#5? Do you have SEM micrograph pictures of pyrolized
corn pollen (charcoal made from pollen) ?  What pollen
do you mean?  Where is the pollen from?  How can the
species of the pollen be determined when it is
charcoal?  Are there other "cell structures" of corn
or cassav present in the charcoal?

>It was reported that corn and cassava pollen was the
main pollen group in these soils.  This would be
independent of the char.  The one thing archeologists
can determine with a high degree of certainty is the
nature of the crops grown on a site. 
 
I don't have a problem with the possibility of using
corn stover or cassava cultivars as feedstock for the
production of charcoal. I just do no see the evidence
that this was the primary feedstock for the production
of charcoal in the Amazon from 4500 to 500 years ago. 
So far, you are telling a story, but have presented
nothing scientific to back up your assertions.  Do you
have any published scientific papers supporting your
claims?  I have not heard any of this before or read
any of it.

>This is my hypothesis drawn from available evidence
and a solid grasp of the constraints visited upon a
primitive farmer.  Actual confirmation came from the
pollen profile, rather than the other way around.
 
Get Johannes Lehman's (from Cornell) book.  Its $229,
but it is the best reference on the original "Terra
Preta" formations found in the Amazon rainforest. 
Also, Christoph Steiner has actually been in Brazil,
studying the development and use of "Terra Preta"
soils.  He is very familiar with trying to grow corn
in the native soils.
 
>The amount of land found covered in "Terra Preta"
soils is claimed to be about "the size of France".  
If there was enough corn and cassava to pyrolyze into
charcoal and put into that soil, then where is all of
the corn now?  What about the cassava?  Neither is
there in the Amazon rainforest now, enough to produce
that much charcoal.

>Corn and cassava are human crops that require human
intervention.  The humans died off shortly after the
new world was first discovered.
 
I do not know the age of the Amazon rainforest?  But,
I would venture that it is greater than 500 years old.
 Brazil has certainly been near the Equator for more
than 500 years. The Equatorial regions of the planet
Earth are ubiquitous with tropical rainforest.  Corn
fields are rare and always manmade.  The nature of
that climate zone and the soil there does not support
corn.  Why isn't there charcoal made from corn in
North America?  There is and was more corn in North
America than there is or was in South America.
 
>That is a very good question.  Why was the technique
not applied throughout the Mississippi valley and
Mexico?  My first conjecture is that it simply turned
out to be largely unnecessary in these soils and field
rotation remained a viable option.  Of course, the
knowledge may simply have never spread from its
homeland. It is a long way without a good intermediary
user.


Regards,
 
SKB


I'm sure that the inventors of terra preta used mud to
cover up their fallen trees and brush to make
charcoal!  It's still made that way in many places
around the world.  In fact that would largely solve
the matter of how they mixed the topsoil and charcoal,
because they are both right there together.  In
contrast, how much effort is it to work all that land
every single year - six inches deep - to mix in a few
pounds of corn stover charcoal for a culture that
didn't even have one single draft animal for
cultivation??  It doesn't seem feasible.  It makes
much more sense to do it all in one shot, considering
the amount of work required to mix the two.

>The difference with corn is that you have ten to
twenty tons of material at hand in a one acre field. 
And it can be pulled by hand.  No other major crop
presents this combination.  The charring process as I
described earlier will naturally mix the produced
biochar with at least an equal amount of earth.  This
can then be carried by basket to the seed hills and
either dug into the hill – unlikely – or simply top
dressed on the hill.

>What we have is a protocol that a stick farmer can
use crop after crop with a minimum adjustment in human
effort that also maintains his fertility decade after
decade.  You simply go from pulling the stalks and
burning them to actually using them to build an earth
surfaced biochar stack.


But how did all this get started?  I'll speculate that
they learned about it by accident.  Perhaps an
understanding of it grew out of their firing of
pottery and the disposal of the wastes?  From the
photos I've seen of some terra preta soil profiles,
they made lots of  
it.  Maybe the quality of their clay was poorer than
elsewhere and they had to make it more often and
thus...??

>I simply think that the nature of the corn root gave
someone the idea to build a stack as I described that
on burning created a lot of biochar which naturally
was distributed to the nearby hills.  This happened on
a rapidly depleting field and postponed locally the
abandonment of that part of the field.   Once the
connection was made, it became fundamental to that
society and led to its huge expansion.

Whatever a month or so ago, Saibhaskar Nakka wrote
about the terra preta 'signatures' he was finding in
India - areas associated with the potter's work. 
Maybe there lies the answer?  Baking of clay within
semi-airtight containment, results in a mixture of ash
and charcoal.  And these wastes were then used by the
potters for their fields.  Maybe this was the way it
all started in the Amazon?

To my mind, the real mystery of terra preta might not
be so much how  the Amerindians discovered how to use
charcoal as a soil amendment,  but why no other
culture did!

>No other culture had a crop like corn which produced
ten tons per acre of dry waste that was actually in a
packable form.  Every other high volume waste is
typically brush-like and it cannot be packed by hand
enough to make it work well.

Gerry



       
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