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terra preta
Terra preta ((:ˈtɛʁɐ ˈpɾetɐ), locally (:ˈtɛhɐ ˈpɾetɐ), literally "black earth" or "black land" in Portuguese) is a type of very dark, fertile manmade (anthropogenic) soil found in the Amazon Basin. Terra preta owes its name to its very high charcoal content, and was made by adding a mixture of charcoal, bone, and manure to the otherwise relatively infertile Amazonian soil. The charcoal is very stable and remains in the soil for thousands of years. 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 earth of the Indian", "Indians' black earth"). ''Terra mulata'' ("mulatto earth") is lighter or brownish in colour.〔"(Discovery and awareness of anthropogenic amazonian dark earths (terra preta) )", by William M. Denevan, University of Wisconsin–Madison, and William I. Woods, University of Kansas.〕
Terra preta is characterized by the presence of low-temperature charcoal in high concentrations; of high quantities of pottery sherds; of organic matter such as plant residues, animal feces, fish and animal bones and other material; and of nutrients such as nitrogen (N), phosphorus (P), calcium (Ca), zinc (Zn), manganese (Mn).〔(【引用サイトリンク】 Terra Preta Web Site )〕 It also shows high levels of microorganic activities and other specific characteristics within its particular ecosystem. It is less prone to nutrient leaching, which is a major problem in most rain forests. Terra preta zones are generally surrounded by ''terra comum'' ((:ˈtɛhɐ koˈmũ) or (:ˈtɛhɐ kuˈmũ)), or "common soil"; these are infertile soils, mainly acrisols,〔 but also ferralsols and arenosols.
Terra preta soils are of pre-Columbian nature and were created by humans between 450 BCE and 950 CE.〔"Historical Ecology and Future Explorations" in "Amazonian Dark Earths: origin, properties, and management" by J. Lehmann, N. Kaampf, W.I. Woods, W. Sombroek, D.C. Kern, T.J.F. Cunha ''et al.'', Chapter 23, 2003. (Clark Erickson), p. 484〕 The soil's depth can reach . Thousands of years after its creation it has been reported to regenerate itself at the rate of per year by the local farmers and caboclos in Brazil's Amazonian basin, who seek it for use and for sale as valuable potting soil.
== History ==
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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