Origin of Biochar - Terra Preta
The technique of using charcoal to improve the fertility of soils originated in the Amazon basin at least 2500 years ago. The native Indians of the region would create charcoal and incorporate it in small plots of land from 1 - 80 hectares in size. Terra Preta, as it is known in this area of Brazil, remains highly fertile until today, even with little or no application of fertilizers. And this is in a region of the world known for its highly infertile soils.
Cross section of soil 1 meter deep comparing Terra Preta on the left, with nearby Oxisol on the right of the type that is normally found in the Amazon basin. [Glaser, B., Haumaier, L., Guggenberger, G., and Zech, W. (2001). The Terra Preta phenomenon: a model for sustainable agriculture in the humid tropics. Naturwissenschaften 88, 37-41.]
Terra Preta sites have been found mainly along the major rivers of the Amazon basin. [Glaser, B. (2007). Prehistorically modified soils of central Amazonia: a model for sustainable agriculture in the twenty-first century. Philosophical Transactions of the Royal Society B-Biological Sciences 362, 187-196.]
A typical Terra Preta site, located on a hill overlooking the river. (Dr Bruno Glaser)
The fact that Terra Preta is highly fertile is well known in this region of Brazil by the local people. They often dig it up and offer it for sale.