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terra preta questions

 
                                      
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Location: Amsterdam, the netherlands
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Hey every-body,

When i searched for terra preta on the forums i had some hits but it seemed to all be in other related topics. so i felt like starting a topic just about terra preta.

cos i have some questions that keep running through my mind.

and i hope that there's people here who can explain more about it.

so as i got it from the people who told us about it:
its this super fertile and healthy soil they discovered in the amazon, that apparantly has been build hundreds of years ago by indeginous people using charcoal, (human) feaces and other organic materials.

the charcoal is supposed to retain more humid and micro-organisms. but, and than im lost, is so good in doing this that is increases without human intervention and using this soil means you never have too manure anymore....

What does that mean? without mulching? these people made it appear as if you could garden/produce in it indefinitely without ever having too fertilize or add anything. Using really advanced permaculture(or comparable) techniques i can see that work. just making the conditions for the natural cycles optimal sounds sensible, and possibly truly sustainible, as in close to being perpetual.

but if they really mean conventional/organic gardening without mulching or any other natural ways of improving the soil they really lose me. Because lots of nice micro-organisms is sweet, but they need organic matter to break down in available nutrients for plants to grow.

And i can understand that charcoal in the soil keeps nutrients longer without leaching, and water i presume. I can get that terra preta will enable you to grow for much longer, and would make your (soil)system more efficient.

So anybody familiar with the subject? the last people i spoke to couldnt really explain it to me, and were not interested in the science behind it, but i am. i want to know all about the processes behind it. so this last conversation was very frustrating.

somebody?
grtz
 
                                
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I know we have discussed it before but couldn't find much either. Maybe someone will chime in.
 
Jordan Lowery
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there is a lot about true terra preta that we do not know about. for  example, its ability to "grow" back after being harvested. some south american natives, come in and harvest the topsoil. say the terra preta was 6 ft deep before they took any soil. now say they take 3 ft of the terra preta. whats amazing is in a few years they can come back and there will be 6ft of TP because it grew back. there is still so much to learn about it.

but as far as adding charcoal to the soil in my climate i highly recommend it, not only does my soil hold more water later into the summer, it holds fertility, actually builds fertility, makes the worms multiply like crazy, make plants grow better period and much more.
 
                                      
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this is what i get, superfertility, and regenarative abilities, ok.

but it seems to me that this is not completely new. i mean nature has this ability of building soil, i can get that we can accelarate this by adding charcoal and feaces once. BUT soil without vegetation (or added organic matter for carbons nitrogens etc.), cannot build soil out of nothing.

if you look up the thermodynamic laws, a set of natural laws that are on the basis of science.
(we actually got this in a pdc in germoney, but we also got the terra preta thingy, which contradicts each other as far as i get it)

its just not possible to create stuff from nothing, those microorganism in the soil that make soil out of organic matter still need organic matter (energy from the sun caught and stored by plants). its almost as if a perpetuem mobile in nature is found. the impossibility of perpetual movements is one of the things that the second law of thermodynamics states.

and i dont want this to become some scientific bladiblah, science isnt everything. but, i would like to know if this perpetual thing is just a misinterpretation of a great soil concept, or if the story of terra preta is actually based on such an assumption.

so im hoping for anybody who knows more about it?
cheers
 
Brenda Groth
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well i don't know much about the TP but I do know that char is a great benefit..i have been using it now for a while in some areas and it has great fertility
 
Joel Hollingsworth
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There is so much leaching in the area, that it is a real struggle to maintain nutrients, even when all locally-used nutrients are returned to the soil. The leaching is so extreme that all lime and silica sometimes wash away, leaving a high-grade aluminum ore.

What would be a closed loop in a lower-precipitation climate (like Europe) is an open loop in the rainforest, because plants can't grab all the nutrients in time. With terra preta, you still have to manure, but you don't have to go foraging for outside sources of fertility as you would if you farmed on the natural soil.

Two components that are often mentioned in the literature, but haven't yet been mentioned in this thread, are fish bones and potsherds.

Another thing I'd like to reiterate, is that terra preta seems to have been made from a low-temperature charcoal. Methods that would produce a good fuel, may result in too-thorough pyrolysis in terms of what's best for the soil.

The regeneration makes some sense to me. Low-temperature pyrolysis has a similar residue to slow decomposition, and nutrients flow through a vibrant rainforest ecosystem so rapidly that the soil would probably have a lot of good stuff fall onto it over the course of a few years.

I'm certain that this is not a recipe for violating the laws of nature.
 
Emerson White
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soil wrote:
there is a lot about true terra preta that we do not know about. for  example, its ability to "grow" back after being harvested. some south american natives, come in and harvest the topsoil. say the terra preta was 6 ft deep before they took any soil. now say they take 3 ft of the terra preta. whats amazing is in a few years they can come back and there will be 6ft of TP because it grew back. there is still so much to learn about it.


And they will sell you all 6 feet of it for only 1.5 times the price .
 
Joel Hollingsworth
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Emerson White wrote:And they will sell you all 6 feet of it for only 1.5 times the price .


I'm not sure I get it. You're implying that it's a scam?

The business model is, unquestionably, one of extracting nutrients from the forest, and selling them to gardeners. The anecdotes of soil regeneration weren't originally part of a sales pitch, they came from academic types interviewing the people who sell the stuff.
 
Emerson White
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Joel Hollingsworth wrote:
[T]hey came from academic types interviewing the people who sell the stuff.

A good salesmen never stops.

Tera Preta gets its dark color from charcoal, charcoal does not reproduce itself, it must be made at high temperatures (think at least 400 F) there for it is impossible for the tera preta to grow itself. It can be mixed in with other, inferior, soils and produce a fairly dark soil that could be sold as tera preta if you had the right salesmen hustle. some of that mixing would happen naturally too, roots can push the soil around a bit underground a they grow, but charcoal and pottery shards do not reproduce themselves,

 
                                      
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yeah, i guess im just trying to filter out the known features of terra preta from all the boosted up story's from the ones who sell it.

and the things joel mentioned,  comes closer to what i thought of it:
fertilizing still necessary but the soil capacity to retain water and nutrients is improved.

indeed, thinking about the tiny topsoil layer of rain forests and the constant run trough/cycling of nutrients and energy, versus the deep top soil we enjoy here in europe its advantages could be limited here...

thanks for your comment joel.

i do tend to think a big part of the story as it reached me (through attending a pdc in germoney) is way boosted, i guess by people selling it. as in my opinion is every perpetual growth story.

selling terra preta is not necessarily a scam, although i wouldnt sell amazon forest soil. i guess nothing wrong trying to sell newly made terra preta. or trying to learn from such a successful method.

but if u ask me some stories are boosted, and (wrong) assumptions were presented as facts. anywho i will first read up on the claims of companies selling this before making such bald a statement.

does anybody has any knowledge on how much to ad to your soil. how much char compared to manure and/or fish remainings? also what type of charcoal is good. i guess regular bbq packs are no good?

It sounds like a good way to improve our sandy, dry and leaching soil on the urban building site we are gardening here.

thanks
 
Joel Hollingsworth
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Joop Corbin - swomp wrote:how much char compared to manure and/or fish remainings? also what type of charcoal is good. i guess regular bbq packs are no good?


Briquettes have a binder in them, and can be way outside the mineral content you would want.

As I mentioned above, good fuel will probably be overcooked as a soil amendment. I've read it still works OK, but not as well. I make my own, and crush it.

I don't know how much charcoal to add, because I don't make nearly enough relative to the amount of compost I make. If I suddenly had a surplus of charcoal, I'd do some trial-and-error as follows: start a compost pile with somewhat fewer browns than usual, and enough charcoal to be significant in the decomposition process but not enough to stifle activity, based on my intuition of how compost tends to go. Something akin to the Indore method or biodynamic methods, but with charcoal as a more-potent replacement for lime & soil. Given enough starting material, I'd make a few piles with different mixtures. In a few months, I'd turn them and see how it all went.

Emerson White wrote:
A good salesmen never stops.

Tera Preta gets its dark color from charcoal, charcoal does not reproduce itself, it must be made at high temperatures (think at least 400 F)...charcoal and pottery shards do not reproduce themselves


I hear you about potsherds not re-generating, but highly-stable organic matter does. Lignite, humic acid, partially-pyrolized wood all end up resembling one another in color, bulk chemistry, and even surface chemistry. Even though they take different paths, the same thermodynamics determines their beginning and ending points.

If I were in the business of growing things, and was told that a product I'm in the market for could re-produce itself rapidly, I would be inclined to buy less of it, not more. Maybe I just don't understand salesmanship.
 
Emerson White
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On the marketing I think that Jevons paradox comes into play, while someone with a fixed need to fill might buy less (for a higher price) there are also people who are willing to buy more to fill a bigger need and people willing to buy any at all because they see it as having a higher value. Additionally how would you know that it was 6 feet deep originally if you only dug out the first three feet? Perhaps they dug a test hole to see how deep it was but that would only tell them about one location, it would tell them nothing about the whole field.

As for it growing itself, I'm not sure about the chemistry. To my knowledge the char in tera (one "r" or two?) preta works just like the activated carbon in an aquarium, forming covalent bonds with more volatile organic compounds and holding onto them, the surface chemistry would in due course trend towards that of the organic compounds that are being bound on the surface. It captures those dissolved organic compounds and the enzymes that the bacteria have released to break them down no longer fit onto them and it allows them to stay in the soil, so I could see the mass of the soil increasing over time as plants grow and die and roots rot apart in the soil, but I would expect a few milimeters over 25 years, not a few feet. In really sandy porous soil with good agitation you might see a few inches. Furthermore if tera preta were able to grow itself why isn't it all over the amazon by now? Everywhere that a camp has ever been set up there are high nitrogen scraps with charcoal, fires happen in the Amazon on occasion I would imagine, at a rate of an inch and a half a year I'd expect the whole of the amazon basin to have been converted thousands of years ago.

I just don't think that there story makes much sense, and I've looked at the problem from a few different angles as you can see. Do you see what I mean?
 
Joel Hollingsworth
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Emerson White wrote:I just don't think that there story makes much sense, and I've looked at the problem from a few different angles as you can see. Do you see what I mean?


I do see what you mean. And in principle, I tend to agree.

I think the growth rates in the anecdotes wouldn't be sustainable long-term, as they would be drawing on local sources of nutrients. A surrounding jungle can replace what hand labor can remove from one isolated spot, over the course of a couple years. The reserves embodied in the large deposits of terra preta we see today are widely acknowledged to have been built up by importing marine products and carefully conserving locally-harvested resources over the course of several centuries, and on the scale of an entire civilization.
 
erich Knight
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Yes , Terra Preta (TP) soils do grow back.
Landscapers harvest only a few inches and because of the bioturbation of all the Wee-Beasties in these six foot deep black soils they grow back at record rates compared to normal topsoil growth rates.


A Recent paper by C. Steiner adds More logs on the Research pile for our Non-Combustion fire.
We can add major savings of N, in Poultry litter composting with Char shows that 50% of Nitrogen is conserved in the compost-Char finished Compost!!

Also Among the concomitant benefits  Julie Major's Ca and Mg nutrients result ;

A new article from Dr. Julie Major's PhD dissertation, out online. Reports on a 4-year field trial set up by Marco Rondon while at CIAT. Shows maize yield increases and improvements in soil fertility.

Maize yield and nutrition during 4 years after biochar application to a Colombian savanna oxisol
http://www.springerlink.com/content/n073641q14661246/

and beyond  that are the several value streams that chars may be called to duty for and thus different valuation. These ecological services also cross over with the usual Ag/soil benefits.

Soils and sediments;
in situ remediation of toxic agents, and the list is long; Heavy metals, Dioxins, Over dosed pesticides & herbicides, In fact I was just contacted by my local Dupont facility, with historic mercury problems, and sent them the recent ISU presentations and other papers on this application.

Feed Rations;
Again a cascade of benefits through the system,as it were;
GHG reductions,  reduced animal Ammonia respiration in confinement thus better feed conversion & general Health thus less antibiotics, Darker litter that easier to sell, or with ranging animal free char spreading.


Suffice to say, that there are a plethora of ways to skin this Biochar Cat.


US Biochar Conference at ISU;
To access the presentations, go to:  http://www.biorenew.iastate.edu/events/biochar2010/conference-agenda/agenda-overview.html, and click on the title of the session you want.


Biochar Sorption of Contaminants
http://www.biorenew.iastate.edu/events/biochar2010/conference-agenda/agenda-overview/breakout-session-5/agriculture-forestry-soil-science-and-environment.html



Dr. Lima's work;
Specialized Characterization Methods for Biochar
http://www.biorenew.iastate.edu/events/biochar2010/conference-agenda/agenda-overview/breakout-session-4/production-and-characterization.html

And at USDA;
The Ultimate Trash To Treasure: ARS Research Turns Poultry Waste into Toxin-grabbing Char
http://www.ars.usda.gov/IS/AR/archive/jul05/char0705.htm


Much More on this Biochar Soils Thread posted in Permaculture;

http://www.permies.com/permaculture-forums/4693_0/permaculture/re-biochar-soilshusbandry-of-whole-new-orders-amp-kingdoms-of-life
 
Emerson White
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I'm sorry if you posted it, but do you have any litterature that shows Terra Preta growing? Is it growing itself or is it making standard topsoil around itself? Are the types of activity that people are doing on it growing the topsoil or is just lying fallow working? I'll believe that people gardening and mixing in compost will improve the soil over time, maybe even deepening it, but to my knowledge it will not have the same composition as TP.
 
Jordan Lowery
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Tera Preta gets its dark color from charcoal, charcoal does not reproduce itself, it must be made at high temperatures (think at least 400 F) there for it is impossible for the tera preta to grow itself.


i was very skeptical of soil "Growing" myself, but its a known fact that it does happen. no one is saying the char itself is reproducing, but somethings going on.

also there is a lot more than just char in the TP soil, a lot more going on than we have pictured.

but i will say in most soils, char will benefit anyone greatly. over the years of using it i have seen it  increase fertility, stimulate biology, increase water retention, and much much more in a wide range of different soils.
 
erich Knight
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Hi Soil ,
yes, no new char has been made, but biotubation brings it up through the soil profile to mix with the new leaf litter during the agreed on fallow time before more TP is harvested.
I havn't seen any papers quantifying this process, just reports of this informal practice by local farmers/Landscapers.


Now this sounds really *Exciting!* a $364K grant from NASA's Space Archeology program, so we will soon know the true extent of TP soils, not just the estimated 11% of Amazonia (size of France) numbers thrown around;

[size=10pt]UNH scientist to estimate pre-Columbian Amazonian population using satellite
imagery
[/size]
Michael Palace, a research assistant professor at the Complex Systems
Research Center (CSRC) within the Institute for the Study or Earth, Oceans, and Space, is an expert in using satellite-borne imagery to study various
aspects of tropical forests. In this project he will use hyperspectral
imagery taken by NASA's Hyperion sensor onboard the Terra satellite.
The Hyperion camera "sees" in 242 spectral bands of light, allowing scientists to identify the chemical makeup of tree leaves, which in turn is
related to nutrients in the underlying soil. The more nutrient-rich leaves
or specific groups of tree species seen by Hyperion will be the signature
for what Palace is looking for – Amazonian black earths – sites containing
soil rich in organic matter, charcoal, and nutrients and frequently
associated with large accumulations of potsherds and other artifacts of
human origin.

http://www.eurekalert.org/pub_releases/2010-06/uonh-ust060710.php

Here is some more back round on the Satellite TP survey and Michael Palace

Time Traveling Via Satellite
Tropical ecologist Michael Palace comes full circle with a NASA Space Archaeology grant to estimate the population of pre-Columbian Amazon indigenous peoples
MICHAEL PALACE majored in archaeology and environmental science at the University of Virginia, then turned to the environmental science side of things as he pursued his master's degree at UVA. For his thesis he studied the dynamics of Costa Rican howler monkeys in relation to landscape-level vegetation structure.

http://www.eos.sr.unh.edu/newsl_0610/palace.shtml

Cheers,
Erich
 
Emerson White
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soil wrote:
i was very skeptical of soil "Growing" myself, but its a known fact that it does happen


I think you are using the term "known fact" a little loosely. I think "Often repeated story" would be more accurate at this point, especially if no one has set up a test plot and measured in a scientific manner.
 
Joel Hollingsworth
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Emerson White wrote:
I'm sorry if you posted it, but do you have any litterature that shows Terra Preta growing? Is it growing itself or is it making standard topsoil around itself? Are the types of activity that people are doing on it growing the topsoil or is just lying fallow working? I'll believe that people gardening and mixing in compost will improve the soil over time, maybe even deepening it, but to my knowledge it will not have the same composition as TP.


My understanding is that non-human activities make topsoil in these anecdotes, especially the re-vegetation of places that have been dug up, and normal animal activities that the plants allow. Topsoil formation is greatly speeded up in the environment fostered by the terra preta. Components of terra preta that are not the result of decomposition get diluted in the process, but the result still does not resemble the surrounding topsoil (at least, not for a few cycles of harvest and fallow).
 
Denise Lehtinen
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This is what somebody said about this in another group I'm a part of:

There is a black soil in the Amazon called terra preta - it's a man-made
soil based on years of accumulated bio-char, usually from charing the
spent crops (which is about the only way to keep the jungle at bay too).
As a result, these plots are super rich because the pores in the charred
material are like nutrient batteries, capturing and sequestering
nutrients from the frequent rains before they can leach away.

When I get my greenhouse dug out, I'm going to have the floor scraped
clean. It's pure white sandstone - actually pretty hard sandstone for
the most part, but it breaks up into a powder-fine pure white sand. I'll
have the digger scar the floor with the backhoe bucket to give me a few
inches of sand in the bottom when he's done.

I am then going to start collecting woody weed stems - like those of the
giant ragweed we have growing here, and twigs and such. No big chunks of
wood and no hardwood - too hard to pulverize into a powder. I'll get a
burn barrel and stuff it full of this material and make some charcoal
out of it right where I'll be depositing it. A few barrel's full should
make enough to get me started, methinks. I'll take a tiller and till
that into the pure sand thoroughly, then mix in some finished compost, a
bit of lime and perhaps some colloidal phosphate clay and maybe some
volcanic ash or pulverized volcano sand. And that'll be my new topsoil.
More or less. It'll have to mature - form a soil foodweb. When I plant
trees, I'll dig into the sandstone below the topsoil so eventually
there'll be lotsa little pits in there that'll have sand and charcoal
and compost so that'll increase the depth of the topsoil too.

I have perhaps 8-12" of sand in the bottom of my pit now and outside the
greenhouse enclosure that sits in the pit I have a volunteer basswood
tree and a willow tree that are growing quite happily. I'll have to
remove them, of course - this winter I'll dig them up and heel them over
in my sand-pile while I find a place to plant them. But it is promising
that trees can grow even in that little bit of loose sand. The taproots
may have found soft parts of sandstone to snake down towards the
water-table too. I expect my tropicals to perform similarly. Hopefully,
with them tapping into the water-table just 8' below the bottom of the
greenhouse, I won't have to water as much. That'd be convenient. Of
course, I'll have plants in there that don't form deep taproots so
they'll have to be irrigated and I may tap my fish-tanks for that, or
pump in rainwater thru overhead sprayers inside the greenhouse whenever
it rains and fills the rain-bucket from the gutters - a simple sump-pump
with a float-switch would do that automatically. Ooh - that's be an easy
way to foliar feed with humus tea and whatnot too - just switch off the
pump, brew humus tea in that same barrel (worm castings, a bit of
molasses and lotsa aeration) for 24 hours, then switch on the pump and
watch it spray my plants happy.

Anyway - converting pure sand to terra preta will be an interesting
experiment. I'll keep the burn barrels and keep adding char to the
greenhouse over time to build it up good. I guess I'll probably want to
add char into the bamboo bed that'll be growing up topside too...

But I soooo look forward to fresh avocados, oranges, macadamia nuts,
cherimoya, coffee, chocolate, vanilla, piper-pepper, guava, pineapple
and much more from this new soil...

I guess I'll need to have large flaps on either end of the hoop-cover to
open so that bees can get in and out on nice days. The glazing may be
clear, so hopefully they'll be able to navigate easily enough to the
large openings rather than bumping hopelessly into the glazing - but
even then they should be able to get out easily enough. My avocado has
been flowering in the early Spring when the bees could be pollinating it
but it's been too cool to remove the cover altogether - but warm enough
that large vents on either side can be opened. I can cover the vents
with chicken-wire to keep out birds and critters. My orange has flowered
too but it doesn't need a pollinator, fortunately - tho surely it'd
benefit from one. My coffee will need pollinators tho. Maybe I'll bring
in some mason bees into the greenhouse too... Ideas ideas - I so look
forward to digging that out more and expanding it. My wife getting
permanent work will help enormously and that will happen very soon.

Be well,
Mike

from http://www.taroandti.com/ Exotic Plant Info and More...
 
Denise Lehtinen
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Also you don't want to use store bought charcoal... it has nasty things in it.

The simplest way to make charcoal is to burn wood in an oxygen deficient environment.  Any campfire (at least the ones I make) always makes some of it.  I've been making mine in a small grill with a cover.  Get the fire going and put the lid on.  I can only make very small batches this way, but it is easy to do.

The simplest way I've found to turn it into a powder takes a page out of how some women in Africa make flour.  Their method consists of a big old heavy ceramic jug and a big old tree log that is wider on the bottom to pound it with.  My method uses a ceramic flower pot without any drainage holes in it, and a stick from one of the weedy trees around here that I was going to make into a handle for a home-made sidewalk edger.  In both methods you get to do the pounding standing up -- which is nice.

The charcoal works by absorbing the nutrients that fall on it via the rain, etc.  This ability of charcoal to absorb nutrients is also used medicinally as a treatment for some forms of poisoning.  You'll find it sold at your local drugstores for that purpose.  So, it isn't at all new that charcoal has this ability -- it is only new (to most of us) that that can be used to advantage in building soil fertility.

 
Kota Dubois
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When I was a small boy I spent a lot of time with my old style farmer grandfather (one of the greatest influences in my life). One day we were in a field and he would pick up bits of earth and taste it. When I asked why he did that he said he wanted to know if the soil was sour or sweet, and this soil was sour and needed to have charcoal added to make it sweeter.

When I first read about biochar a while back I asked a biochemist who I know what might be happening with something as inert as charcoal de-acidifying (sweetening) the soil. Without missing a beat he said it gave off carbonate ions which neutralized the acid. I wonder if this isn't the largest part of the success of biochar.
 
William Roan
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Biochar is pretty fascinating stuff and I would like to give my best guesstimation of what is happening. After watching the video, “The Secrets of El Dorado”

http://video.google.com/videoplay?docid=8993313723654914866#

I am convinced that the Terra Preta formations are part of a classic ceramic pit fires, similar to Raku firings. Before there where kilns, primitive ceramicist would have dug deep holes filled the hole with their pots and started the fire.

http://www.eos.sr.unh.edu/newsl_0610/palace.shtml

Look at the third picture (thank you Erich) I’ve never seen this picture before, but I think it supports my Hypothesis. The blackened soil is contaminated with the pit fire smoke, burnt organic material and ash. But notice the lighter brown soil, which suggests the foot print of where the greenware pots were stacked.
There are four large black footprints, located in the hole that shows where the burning took place. Because the Amazon is so humid the greenware clay body would have retained a lot of water. So the firing would have to start out at a low temperature. The pit temperature couldn’t rise above 120 degrees, the boiling point of water. Otherwise the side of the ceramic pot would get a steam explosion and blow out the side of the pot. The pot shards would blow into the fire and continue to pop until they either became smaller and smaller pieces or the water evaporated out of the clay body. The remaining parts of the exploded pot would have dried out and acted like a bag wall or a buffer wall to protect the inner stacked pots from a sudden rise in heat.
What I’ve read, there is a far amount of burnt rock also found in these formations. With a learning curve, I would think that large rocks began to be used as bag walls and avoiding the loss of the first roll of pots.
Once the clay body water has evaporated out the fire and temperature can be increased. So how do you know if the water has evaporated out? Are the pots no longer exploding. In a modern kiln you sniff at the glory hole, it smells acidic until the water is removed. (Ok Paul, I might get cited, but these are ceramic terms) You can hold a mirror about the glory hole with the glass facing down, steam will condense on the glass if there is still water in the kiln. It could have been as simple as putting a piece of organic material like moss on the top of the pot stack and wait for it to dry out and turn brown. I didn’t know.
The fire is built up until 600-850 degrees has been reached in the pit. Now the temperature has to be maintained until the molecular water has time to evaporate out of the body and the clay body can go through quartz inversion. Again if the molecular water boils at the higher temperature there will be a steam explosion. So again it would be important to protect the ceramic works with a stone bag wall. See above method of predicting when the clay body water has been removed, it similarly applies to the molecular water.
After the molecule water has been removed, wood and other organic materials would be added until there was a huge blaze bring the temperature up to I’m guestimating 1100-1800 degrees. But I would think more towards the lower temperatures, judging from what I’ve seen from museum pieces.
Now the biggest danger is from crushing the pots, when throwing wood onto the blaze. The fire would be allowed to burn itself out or soil could be thrown on top to snuff out the flame and help hold the temperature in the fire pit. After the pit had cooled, the soil, pot shards, charcoal and ash would have been thrown out of the pit to retrieve the whole pots.
As the ceramic community began to create the next batch of greenware, human nature tells me that the open pits would have been used as a trash pit, which would explain the bones and a mixture of organic materials.
When the pit fire site was finally abandoned it would have filled in with organic forest materials to create the rich black soil we see today. But that’s my hypothesis.
FYI
I few years ago I was watching a ceramic teacher, going through his stack of ceramic mugs that had just come out of a firing. They all looked fine to my eye, or at least useable. But he was smashing everything that wasn’t perfect. I wonder if human nature wasn’t the same with the ancient pit fire artists.

Many years ago the ceramic department took the students out to a cleared area, off campus to do pit fires and raku. The students were sitting around all night maintaining the fires and noticed the smoke was coming out of different locations in the ground not associated with their firers. They later found out that the area was a wooded forest that had been bulldozed down and covered with dirt. All those underground trees caught fire and were spreading underground. The fire department spent a week trying to put it out.






 
erich Knight
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I tend to agree with BiologyBill,
Moira Wilson of the University of Manchester has developed a ceramic dating technique which sounds perfect to draw an exact time line of TP development year over year.
At an accuracy of years we could see the speed at which the system built on itself once initiated.
Archaeological dating by re-firing ancient pots - physicsworld.com
http://physicsworld.com/cws/article/news/39413

My reviews of the agronomic field trials & literature using Biochars clearly show consistent positive effects in temperate & tropical soils, what is not known, and in debate, are some of the mechanisms for the "black box" nature of biochar effects : MYC / AMF & microbe refuge theory, Glomalin soil aggregation & water films, microbial mats & quorum sensing, expansion of aerobic soil horizons & suppression of the anaerobic. As a feed ration for livestock & aquaculture; http://superstoneclean.com/video-presentations/
and the most startling, plant chemical signaling for expression of dormant genetic traits.
http://terrapreta.bioenergylists.org/content/trials-maize-reactivating-dormant-genes-using-high-doses-salicylic-acid-and-charcoal

I sent DuPont work with heavy metals last year which initiated field trials Hg showing a 95% reduction of food web uptake! Their lab bench results showed good binding, but did not hit 95% reductions until the in situ study with the full complement of microbes, fungi and the bioturbation's of macro fauna.

This same problem remains for explanation of the mechanisms of other char applications, The internal biology changes when char is used as a feed ration, The role of Phosphorous chars for both plant availability and an heavy metal binding remediation techniques. The intricacies of fostering increased aerobic conditions into deeper soil horizons, I'm just so glad we have all these positive affects that tantalize
researchers and will build funding support to answer the mechanism questions.

What the CFC / Ozone success story was for raising the importance and attention to atmospheric chemistry, I feel biochar soils will be for carbon soil chemistry, Mycology and Microbiology.

So Much work to be done,




The Terra Preta Prayer

Our Carbon who art in heaven,
Hallowed be thy name
By kingdom come, thy will be done, IN the Earth to make it Heaven.
It will give us each day our daily bread and forgive us our atmospheric trespasses
As we forgive those who trespass against the Kyoto protocols
And lead us not into fossil fuel temptation, but deliver us from it's evil
low as we walk through the valley of the shadow of Global Warming,
I will feel no evil, your Bio-fuels and fertile microbes will comfort me,
For thine is the fungal kingdom,
and the microbe power,
and the Sequestration Glory,
For ever and ever (well at least 2000 years)
AMEN
 
I agree. Here's the link: http://richsoil.com/email
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