Monday, July 09, 2007
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....."
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."
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." Additionally, "....Thus far, despite great effort, scientists have been unable to duplicate production of the soil." 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.”
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."
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."
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....."
Terra Preta soils have tremendously high fertility. Researchers claim "....terra preta can increase yields 350 percent over adjacent, nutrient-leached soils." Also note, however, that "Amazonian dark earths have high carbon contents that are five to eight times higher than the surrounding soil...."
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."
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." 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."
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."
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."
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."
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