What is Terra Preta ?
Terra Preta (or: Red Indian Black Soil) is an anthropogenically (man made) modified, fertile soil, which has developed in small patterns from the unfertile Latosols (Oxisols) in the Amazon lowlands. Influence of man is shown by abundance of many artefacts (ceramics) of prekolumbian Indians, which have been living in these areas some + 2000 years.
It is not absolutely sure, if primarily Terra Preta existed and Indians selected these sites because of their fertility, or if Indians have 'modified' the soils of their dwelling sites by mulching and compost.
In soil terms, Terra Preta is to be defined as a subtype of Latosol, which has a high till very high C content (more than 13-14 % organic matter) in its A horizon, but without hydromorphic characteristics. Organic matter can be found in depths of 1 and 2 m (e.g. at 50 cm depth, 5.1 % OM). The author made the proposal to talk of TP only, if OM content at 50 cm depth is of more than 2.0 or 2.5 %.
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