Origins of Amazonia's Terra Preta Soils

I have been convinced for some time that the Terra Preta soil in any given location is far more than just black carbon supplementation derived from slash and char techniques. I believe, based on my research of online source material on Terra Preta that each patch of Terra Preta soil (there are hundreds, even thousands of such sites known throughout Amazonia and more being discovered each day) has been seeded with Terra Preta soil from another (previous) location. I believe these Terra Preta soils have their origins in the first agricultural efforts on carbon-rich volcanic soils in northwest South America (Ecuador and Bolivia) as land migration into South America from Central and North America by ancient indigenous peoples proceeded.

I am guilty, as are most, of focusing my research on garnering support for my theory and, consciously or subconsciously, rejecting that which does not support it. That having been said, however, I do believe there is a preponderance of research material that is supportive. Following are a number of pertinent quotes from source material that I believe bolsters my position.

Terra preta soils "....contain microbes that are uniquely associated with soils high in BC as compared to adjacent soils....."[1]
There is "....a greater homology between sequences obtained from the four TP sites than between sequences obtained from adjacent and non-TP soils from the same site."[1]
Scientists are having difficulty in developing answers to the Terra Preta mystery. There remain "....many questions still unanswered with respect to their origin, distribution, and properties."[2] Additionally, "....Thus far, despite great effort, scientists have been unable to duplicate production of the soil."[3] The realistic conclusion of the researchers is, "....At the moment, there is a lot of excitement but there’s a lot of work to do.”[3]
Despite many consistencies in Terra Preta soils at different sites, the native characteristics of the altered soil result in many "....varied features of the dark earths throughout the Amazon Basin."[2]
The differences in carbon content in Terra Preta soils suggests that it is not natural in that "....the total carbon stored in these soils can be one order of magnitude higher than in adjacent soils."[2]
The structural similarity of the carbon in Terra Preta soils to charcoal has consistently led researchers to assume that the ".....purposeful application of organic carbon from incomplete combustion may have been the primary reason for the high carbon contents....."[2]
Terra Preta soils have tremendously high fertility. Researchers claim "....terra preta can increase yields 350 percent over adjacent, nutrient-leached soils."[3] Also note, however, that "Amazonian dark earths have high carbon contents that are five to eight times higher than the surrounding soil...."[4]
In a practice that may mimic the original development of widely dispersed Terra Preta soils, "Truckloads of the dark earth are often carted off and sold like potting soil."[3]
A clue to one key aspect of Terra Preta soil is scientific belief that, "....fish residues are an important portion of the high phosphorus concentrations. Phosphorus is really the number one limiting nutrient in the central Amazon."[3] This suggests that the original development of Terra Preta soil may have occurred closer to the sea, on the northwest coast of South America, rather than in Amazonia.
An important key to the uniqueness of Terra Preta soil and, I believe, an important indicator that it may have been seeded from previous sites, is contained in this statement. "You can have the same amount of carbon in terra preta and adjacent soils and the infertile soil won’t change."[3]
Philip Coppens reveals one of the most salient points supporting seeding when he states "....most now argue that people altered the soil with a transforming bacterial change."[4]
One of the most tantalizing clues that the development of Terra Preta soils may have accompanied the gradual populating of the Americas is contained in this statement, "....though science may have long forgotten about this technique, in the highlands of Mexico, these techniques can still be seen at night, when local farmers set parts of their field alight."[4]
Finally the tantalizing question of Terra Preta soil's ability to reproduce itself is revealed in this statement. "In fact, one missing ingredient is how the soil appears to reproduce. Science may not know the answer, but the Amazonian people themselves argue that as long as 20cm of the soil is left undisturbed, the bed will regenerate over a period of about twenty years. A combination of bacteria and fungi are believed to be the transformative agents, but the agents themselves remain elusive from the scientific microscopes."[4]
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1) Isolating Unique Bacteria from Terra Preta Systems: Using Culturing and Molecular Tools for Characterizing Microbial Life in Terra Preta
2) Terra Preta de Indio
3) Terra preta: unearthing an agricultural goldmine
4) Terra Preta - Philip Coppens

Terra Preta Soils - Agricultural Miracle from the Past?

Sometimes we literally can't see the forest for the trees. In recent years there has been a great deal of scientific interest in a soil phenomenon in South America's Amazon River basin, a phenomenon called Terra Preta.

Scientists now understand, though they did not until recently, that Terra Preta soils are anthropogenic, created by man. They were, in fact, created hundreds, even thousands of years ago through the efforts of indigenous peoples living and thriving in the Amazon River basin. It was only recently, through efforts to re investigate myths from Spanish explorers about the fabulous golden cities of El Dorado that the forest behind the trees finally started to come into view.[3] It was through those efforts that the full extent of anthropogenic Terra Preta soils in this area were finally realized. It is estimated that as much as 10%, maybe more, of the soils in the Amazon basin are Terra Preta soils. Only after understanding these magnitudes did archaeologists finally understand how there had been a sufficient agricultural base to support the vast ancient civilizations (now estimated to possibly number into the millions of people) in the Amazon basin, civilizations that, until recently, had largely been written off as myth.

What is Terra Preta soil? Essentially, and it is a mistake to believe this gives a complete understanding of what makes Terra Preta work, Terra Preta is soil that has been enhanced by black carbon, derived from charcoal, and other organic matter. But there is more. A report entitled Isolating Unique Bacteria from Terra Preta Systems: Using Culturing and Molecular Tools for Characterizing Microbial Life in Terra Preta, states, "The greater fertility of Terra Preta (TP) soils is thought to be due to their high black carbon (BC) content, which contributes to increased nutrient and moisture retention, and increased pH. It is likely that the unique chemistry of BC results in distinct microbial communities involved in nutrient cycling and organic matter turnover.[my italics]"[1] With a number of extensive scientific investigations underway on Terra Preta soil, in fact, scientists are coming to realize that the similarities of the bacterial colonies in Terra Preta soils at different locations, even hundreds of miles apart, are far greater than similarities to the bacterial colonies in non Terra Preta soil in areas immediately adjacent to Terra Preta sites.[1, 2]

Here is where I launch into my own speculation. Throughout the history of man nomadic peoples have carried with them from site to site materials and items that are of critical value to them. The Polynesians as they hopped from Pacific island to Pacific island took with them the seeds, roots and seedlings of particular plants that were important to their culture. Early men, as yet not knowing how to create fire, took great pains to carry embers from one fire to start a fire at a new site.

It is not unreasonable to speculate, in fact, that the original pockets of Terra Preta soil were not made by man but rather discovered by man. Over time they may have realized that adding charcoal from their fires to the soil resulted in dramatic increases in fertility. They may have taken this knowledge to a new site and found, in fact, that it didn't net them the results they expected. It may have been, at that stage, that they returned to the site with the fertile Terra Preta soil, gathered up some of that soil and carried it with them to the new site where they mixed it, and more charcoal, into the soil at the new site. It is very unlikely that they would understand what made the original Terra Preta soil so fertile. It would probably have been a form of magic to them, and that Terra Preta soil that they carried from site to site would have been seen as magical in its own rite.

This hypothesis of mine (I'm not claiming it is original or unique but I have not seen similar speculation in other quarters) would clearly explain why the bacterial population in one Terra Preta site is so like that at other Terra Preta sites but unlike the bacterial population in non Terra Preta sites adjacent to Terra Preta sites. The bacteria in the Terra Preta soil did not originate in the soil that was transformed into Terra Preta soil but originated in a Terra Preta site elsewhere and was transported there by the indigenous people who established the new Terra Preta site. This would suggest that the development of the Terra Preta soils throughout the Amazon basin was spread over hundreds, even thousands of years as indigenous peoples criss-crossed the basin moving from one site to another, taking their magical Terra Preta soil with them to seed the soil at the next site.

Regardless of whether my speculation is correct concerning how the different pockets of Terra Preta soil were created, the important point is this. What makes Terra Preta soil work is not the black carbon from charcoal that has been added to the soil. It is the unique population of soil bacteria in that soil that utilizes and thrives on that high concentration of organic carbon. Terra Preta soil, like all soils, derives its fertility not from the mineral content of the soil but from the tens of millions of micro-organisms that live in that soil and make those minerals and other soil nutrients available to the plants growing in that soil.

My caution is this..... do not go out and add a bunch of charcoal or black carbon to your garden thinking it will give you Terra Preta soil with its wondrous fertility. You can, however, buy bags of Terra Preta soil at some better garden centres that can be added to your garden, along with charcoal or black carbon, that will give the desired results.

One more caution..... To my knowledge no scientific testing has yet been done to determine if the bacteria unique to Terra Preta soils can survive in non-tropical soils, most specifically in soils prone to a winter freeze. Until such testing has been completed I would be cautious about trying to duplicate Terra Preta soil in your garden in growing zones subject to winter freeze.


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1. Isolating Unique Bacteria from Terra Preta Systems: Using Culturing and Molecular Tools for Characterizing Microbial Life in Terra Preta - 16-Aug-2006
Authors: O'Neill, Brendan; Grossman, Julie; Tsai, S.M.; Gomes, Jose Elias; Garcia, Carlos Eduardo; Solomon, Dawit; Liang, Biqing; Lehmann, Johannes; Thies, Janice
2. Terra Preta
3. BBC - Horizon - The Secret of El Dorado (see particularly minutes 45-48)