Terra preta

Terra preta (Portuguese pronunciation: [ˈtɛʁɐ ˈpɾetɐ], literally "black soil" in Portuguese) is a type of very dark, fertile anthropogenic soil (anthrosol) found in the Amazon Basin. It is also known as "Amazonian dark earth" or "Indian black earth". In Portuguese its full name is terra preta do índio or terra preta de índio ("black soil of the Indian", "Indians' black earth"). Terra mulata ("mulatto earth") is lighter or brownish in color.[1]

Homemade terra preta, with charcoal pieces indicated by white arrows

Terra preta owes its characteristic black color to its weathered charcoal content,[2] and was made by adding a mixture of charcoal, bones, broken pottery, compost and manure to the low fertility Amazonian soil. A product of indigenous Amazonian soil management and slash-and-char agriculture,[3] the charcoal is stable and remains in the soil for thousands of years, binding and retaining minerals and nutrients.[4][5]

Terra preta is characterized by the presence of low-temperature charcoal residues in high concentrations;[2] of high quantities of tiny pottery shards; of organic matter such as plant residues, animal feces, fish and animal bones, and other material; and of nutrients such as nitrogen, phosphorus, calcium, zinc and manganese.[6] Fertile soils such as terra preta show high levels of microorganic activities and other specific characteristics within particular ecosystems.

Terra preta zones are generally surrounded by terra comum ([ˈtɛʁɐ koˈmũ, ku-]), or "common soil"; these are infertile soils, mainly acrisols,[6] but also ferralsols and arenosols.[7] Deforested arable soils in the Amazon are productive for a short period of time before their nutrients are consumed or leached away by rain or flooding. This forces farmers to migrate to an unburned area and clear it (by fire).[8][9] Terra preta is less prone to nutrient leaching because of its high concentration of charcoal, microbial life and organic matter. The combination accumulates nutrients, minerals and microorganisms and withstands leaching.

Terra preta soils were created by farming communities between 450 BCE and 950 CE.[10][11][12] Soil depths can reach 2 meters (6.6 ft). It is reported to regenerate itself at the rate of 1 centimeter (0.4 in) per year.[13]

  1. ^ Denevan, William M.; Woods, William I. "Discovery and awareness of anthropogenic amazonian dark earths (terra preta)" (PDF). Archived from the original (PDF) on 24 September 2015.
  2. ^ a b Cite error: The named reference Mao et al. 2012 was invoked but never defined (see the help page).
  3. ^ Dufour, Darna L. (October 1990). "Use of Tropical Rainforests by Native Amazonians". BioScience. 40 (9): 652–659. doi:10.2307/1311432. ISSN 0006-3568. JSTOR 1311432. Much of what has been considered natural forest in Amazonia is probably the result of hundreds of years of human use and management.
    Rival, Laura (1993). "The Growth of Family Trees: Understanding Huaorani Perceptions of the Forest". Man. 28 (4): 635–652. doi:10.2307/2803990. JSTOR 2803990.
  4. ^ Kleiner, Kurt (2009). "The bright prospect of biochar : article : Nature Reports Climate Change". Nature.com. 1 (906): 72–74. doi:10.1038/climate.2009.48.
  5. ^ Cornell University (1 March 2006). "Amazonian Terra Preta Can Transform Poor Soil into Fertile". Science Daily. Rockville, MD.
  6. ^ a b Glaser, Bruno. "Terra Preta Web Site". Archived from the original on 25 October 2005.
  7. ^ Glaser 2007.
  8. ^ Watkins and Griffiths, J. (2000). Forest Destruction and Sustainable Agriculture in the Brazilian Amazon: a Literature Review (Doctoral dissertation, The University of Reading, 2000). Dissertation Abstracts International, 15–17
  9. ^ Williams, M. (2006). Deforesting the Earth: From Prehistory to Global Crisis (Abridged ed.). Chicago, IL: The University of Chicago Press. ISBN 978-0-226-89947-3.
  10. ^ Neves et al. 2001, p. 10.
  11. ^ Neves, E.G.; Bartone, R.N.; Petersen, J.B.; Heckenberger, M.J. (2001). The timing of Terra Preta formation in the central Amazon: new data from three sites in the central Amazon. p. 10.
  12. ^ Lehmann, J.; Kaampf, N.; Woods, W.I.; Sombroek, W.; Kern, D.C.; Cunha, T.J.F. "Historical Ecology and Future Explorations". p. 484. in Lehmann et al. 2007
  13. ^ Day, Danny (2004). "Carbon negative energy to reverse global warming". Eprida. Archived from the original on 13 September 2021. Retrieved 8 December 2007.