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Terra preta adds fertility to poor soils

Terra preta compared to untouched soil.Amazonians also developed a method called terra preta to increase the fertility of their low-nutrient soils.  Scientists estimate that up to 10% of the Amazon's soil consists of this man-made, high fertility, "dark earth."  Terra preta is high in phosphorous, calcium, sulfur, and nitrogen, is rich in organic matter and microorganisms, and has been shown to have elevated moisture and nutrient retention capabilities.  The soil grows good crops too, even hundreds of years after being created.

Although popular articles about terra preta suggest that all you have to do is create charcoal and work it into the ground, terra preta production is actually more complicated.  The Indians mixed charcoal with excrement and animal bones in long trenches when creating terra preta.  The charcoal consisted of charred wood, weeds, cooking waste, and crop debris.  Copious pottery shards in the terra preta suggest to me that the technique may have begun as simply a modified midden heap.

I'm curious about whether terra preta could be the answer to some of our waste disposal problems.  I try to keep our homestead as self-sufficient as possible, and the influx of cardboard from our automatic chicken waterer microbusiness doesn't seem to fit that model.  I've tossed some of it on the worm bin, but am starting to suspect that I'm overwhelming my poor worms with the mass of sodden cardboard.  (Recycling isn't really an option since we live an hour away from the nearest facility.)  Could I use the excess cardboard along with those troublesome chicken bones and maybe even our excrement to create terra preta?  Only time and experimentation will tell.


This post is part of our American Indian Permaculture lunchtime series.  Read all of the entries:


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terra preta

The writer is a semi-retired energy economist with considerable agriculture in his background and a lot of bioenergy experience. He has never been to Amazonia but can read scientific Portuguese. He has lived and work in Paraguay and traveled to neighboring parts of Brazil. Home base is Carolina, Puerto Rico.

His understanding of "terra preta" is that it is a multi-component soil-management system which includes biomass charcoal, compost and other ingredients including possibly an acid such as urine and/or chards. Do to the haphazard organization of research, we still do not have a clear idea of how the ancients made their charcoal or an adequate understanding of the management systems, which must have varied from place to place, as abandoned sites are found scattered over an area the size of France.

The primary function of the porous charcoal appears to be to provide storage for minerals and a habitat for the microbiota which facilitate the storage and ingestion of minerals by plants. When observed by an electron microscope, the charcoal turns out to have an elaborate interior structure with more internal surface area than external !

The function of the chards, in those cases where their placement is orderly, may be to increase the surface area on which microbiota can "sit" while they do their work of bonding or "snipping" molecules.

The need which microbiota have to attach themselves to something while they "go about their business" has been well established in diverse locations. For exampe, the studies of OTEC heat exchangers carried out off Punta Tuna, Puerto Rico, in the 1980's. The successful "honey comb" anaerobic digester at the Barcardí distillary at Cataño, Puerto Rico, over a decade ago. The distillary obtains all its steam from the burning of biogas obtained by the digestion of distilling-tower "slops", which were formerly dumped in the ocean !

I understand [although some "authorities" deny this] that abandoned sites near Manaus, Brazil, have been "mined" for many years and the resulting "terra preta" sold to commercial farmer in the metropolitan area.

Some extroardinary increses in yield have been obtained both in academic research and commercial operations by the application of "terra preta". We know it can work, but we really don't know how or how to replicate it on a large scale.

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Comment by Lewis L. Smith Thu Aug 27 20:16:27 2009
comment 2
Wow! Thank you so much for all of that information! I'm going to have to read it a few times to digest it!
Comment by anna Sat Aug 29 19:27:40 2009
Human excrement concerns

My understanding is that human urine is sterile when it comes out of the pipe, but it is safest to compost human solid waste at a high temperature and leave it for a year before using it.

Are you using right as it plops?

Comment by WoundedEgo Fri Jan 1 19:33:31 2010
comment 4
You're totally right if you're using the fecal matter straight on the garden. However, my understanding of terra preta is that it was traditionally made in pits that were filled in as you go, a sort of latrine with charcoal, etc. I'm thinking of doing a similar thing in the orchard (which adds another safety factor since the part we will eat is up in the air far away from the poop) --- making pit latrines with the addition of charcoal and maybe other organic matter, then filling them in and hoping the tree roots will find them. Still in the planning stages, though!
Comment by anna Sat Jan 2 08:52:39 2010

The shipping and packing supplies you are not able to recycle are nothing more than a carbon source for your use. At the very least you should be able to cut or shred if possible any of this material and put in the compost. It can also be made into a fuel for your wood stove. There has to be many other ways of using this resource you have, like using it as a building material. Look up "Papercrete", like this site http://www.papercrete.com/cheap.html, there are others. So much information - So little time.

Comment by Vester Mon Jan 11 17:32:48 2010
I agree that cardboard is an asset --- I just haven't found the best use for it yet. I suspect that if I had a good way to shred it, it would be easy to compost, but last summer I threw whole sheets in the worm bin with little luck. Currently, I'm trying to grow mushrooms on it. I'll keep exploring options!
Comment by anna Mon Jan 11 19:05:10 2010

I don't know what changed but I was having issues loading your site (to the point I couldn't even comment to tell you) since December but Magically today it just popped up with no issues. I have been missing out on your pictures, I am so glad to have it back.

Have you thought about using some of that cardboard or anything else you have in the barn that could trap air movement as insulation for the walls and ceiling of your shed? Anything that will slow or block the transfer of air can help.

Comment by Erich Tue Jan 12 11:02:41 2010

I don't know what happened, but I'm glad you're back!

That's another great idea for cardboard! We're definitely going to insulate the shed --- had planned to just buy fiberglass insulation, but maybe cardboard would work in spots. I wonder what its R value is?

Comment by anna Tue Jan 12 16:23:03 2010

Corrugated cardboard should work pretty well as an insulator, I think. People are building complete houses out of it.

The problem is that you have to keep it dry, otherwise your insulation would be rotting away between your walls. You'd get more mushrooms than you bargained for. :-)

Comment by Roland_Smith Thu Mar 18 19:22:09 2010
I guess cardboard houses aren't just for the homeless any more. But how do they keep blowing rain from hitting the walls and melting those buildings right down?!
Comment by anna Thu Mar 18 19:33:30 2010

The outside walls are covered with HDPE.

In my opinion, this house is more like a proof of concept than a real house. And it was designed in Australia; not a continent famous for its rains!

I agree that in a climate like in my neck of the woods such a "house" wouldn't last. Cardboard soaks up water and then looses its strength. Keeping it dry would just be too difficult in a temparate climate.

The Japanese pavillion at the expo 2000 had a load-bearing skeleton made from wound recycled paper tubes.

Comment by Roland_Smith Fri Mar 19 03:07:15 2010
It can stay so damp here for weeks at a time --- sounds like no cardboard for us yet. :-) But I am intrigued by unconventional building materials.
Comment by anna Fri Mar 19 08:27:29 2010
I saw this several years ago. Insulating foam was spray mounded to house size. Then the builders carved out rooms inside. Finally a hardener was sprayed over all outside surfaces.
Comment by Errol Fri Mar 19 10:37:11 2010
Wouldn't you waste more material than you use if you sprayed a bit mound and then carved it out? It seems like using some kind of supports would save a lot of resources (and money.)
Comment by anna Fri Mar 19 18:02:07 2010

Terra preta seems like an awesome way to naturally process or transform your organic waste as well as your cardboard.

If you are still finding that you have an abundance of cardboard after putting in your vermiculture bin & your terra preta mound, you could try using the extra cardboard to kill weeds when starting up new no-till garden beds. You can even use the terra preta that you've made to go on top of the weed-killing cardboard to use for your planting.

Here is a link that includes steps to making a Permaculture garden with the use of cardboard:

http://permaculturenews.org/2013/07/08/an-easy-way-to-start-a-new-permaculturegarden/

Comment by Kate Mascarenhas Thu Jun 5 07:44:28 2014

One very unique homestead, $1,500 per acre, the opportunity of a lifetime