Science Forums 2

[RBlack]

To Malcomf, You have a very good point on how Terra Preta was made. I have inclosed a set of notes (first draft) that I will be using in a talk on March 15 to a combination of the local Sierra Club and and as many garden clubs as we can get to come. This is the introduction part. I will also show how to make charcoal at home and finish with the carbon sequestration piece.

I am trying to char up my kitchen wates and am going to char (if possible), cow and horse manure, and pine needles both dried and fresh. I am working on a way to make some of my char with a lower ph and that is why I will try the pine needles. All this is experimental and for every sucess I have I also have something that ends up like....(cow and horse manure).

RB

Charcoal as a soil amendment: The Terra Preta effect.

Between 400 and 1500 years ago the Indians of the Amazonian basin created a type of soil that we now call Terra Preta de Indio or Black Earth. These soils are characterized by their high charcoal/carbon content, increased level of soil organic matter, resistance to nutrient leaching, and high fertility for plant/crop growth. The one factor in common that all Terra Preta soils have is a high level of charcoal (up to 40%), and it is the physical/chemical properties of the carbon in the charcoal that are responsible for Terra Preta's unique structure.
Carbon has the ability to make long chain molecules, adsorb onto its surface both solid and gaseous compounds, and is resistant to environmental decay. When carbon is in the form of charcoal it also retains moisture, makes an environment for microbial life, and improves soil texture. Carbon is the bases for all life and there are more carbon compounds than all the other elements combined. In soil carbon exists in unstable easy to use and recyclable forms in microbes and soil organic matter, and highly resistant stable forms in charcoal. Through the process of weathering and oxidation stable charcoal/carbon will eventually break down into labile forms but this process depends on many environmental factors that differ between soils due to their microbial makeup, parent material, and physical structure of the charcoal/carbon. Not all charcoal is the same as its charring temperatures (350 to 900 degrees), and its parent stock (woody versus non-woody material), give differing types of charcoal/carbon unique properties and nutrients when added to soil.
There is extensive debate in how the Amazonian Indians created Terra Preta soils as their cultures did not survive the initial meeting with European explorers so we have no first hand knowledge of the process. What can be inferred is that these people used their garbage and latrine wastes to provide organic matter that along with charcoal/carbons unique properties created Terra Preta soils. We don’t know that exact process but in a hot humid environment garbage and latrine wastes would start to smell, attract bugs and animals, and be a source of disease. The Amazonian people most likely found that adding ash and charcoal or periodically burning the top of the garbage/latrine piles would get rid of the smell, alleviate the bugs/animals, and minimize disease. The addition of charcoal in one way or another to their wastes was a hygienic practice that Amazonian Indians engaged in to keep their villages clean and healthy.
What the Indians also found was that the combination of organic matter/charcoal created fertile mix that when added to the nutrient poor soils of the region made them much more productive. In essence they made compost with the unique feature of a very high charcoal/carbon content that gave the soil greater nutrient/water retention while modifying the soil texture for better drainage and aeration.
To create Terra Preta type of soils what is needed is to replicate the practices of the Amazonian Indians. The first is to create charcoal with many unique properties based on charring temperatures, what material is charred, and whether the material is totally charred or partially charred. This was not a process that was exact for the Amazonians nor should it be today as the variability and variety of the charcoal is what provides both stable and unstable carbon and wide range of nutrients in many different forms and compounds. The second factor is what material did the Amazonians char and the anthropological evidence is that they charred or partially charred everything, plants, dead animal, village debris, garbage, their own latrine wastes, and the remains of their most important source of protein, fish.
Village sites and Terra Preta areas most often occur on bluffs near rivers which provided the Amazonians both their major source of protein and their major source of transportation. Even though their Terra Preta areas were still productive if the course of the river changed then the villages would relocate to be close to fishing areas and their transportation source, the river. What the large amount of fish in their diet provides for Terra Preta soils is a source of calcium and phosphorous that ended up in their garbage/latrine areas and then into their soil and back into the plants that they grew. In replicating Terra Preta soils there needs to be a source of calcium and phosphorous added to insure that the conditions and materials that originally created these soils are duplicated today.

RBlack (first draft)