Chemical Properties of Amazon Dark Earths from Southern Amazon.

The Amazon Dark Earths (ADE) also known as “Terra Preta de Índio” are identified by the Anthropic epipedon, and they are a result of ancient Pre-Colombian civilizations activities. These soils present high nutrients and have being pointed as a potential sustainability models for tropical regions. Five sites of ADE where chosen in Rondônia state – Southern Amazon for studying. Profiles with and without anthropogenic epipedons, and variation of land coverage were selected, including forest, pasture, and no till cropping system of soybeans and maize. The horizons were described and samples analyzed according to Santos et al (2013), and EMBRAPA (1997) methodology. The contents of calcium and magnesium were high when compared to the non-anthropogenic soil. This result is usually associated with the presence of animal bones in these soils, although some researchers relate it to the increase of CEC due to the high contents of stable organic matter on these soils. The contents of phosphorus were also very high, up to 451,9 mg.kg^-1. The high phosphorus contents are usually associated to the dietician habits of these civilizations, which consumed foods rich in phosphorous. Sodium and potassium presented low levels in all soils. Apparently, the high precipitation rates of Amazon region led to lixiviation of these monovalent cations in these soils. The CEC of anthropogenic horizons was up to 27,7 cmol_c.kg^-1, while the non-anthropogenic horizons had values lower than 8,07 cmol_c.kg^-1. The low CEC is typical of weathered soils with low organic matter contents. The main aspect in ADE soils seems to be the high amounts of stabilized organic matter and pyrogenic carbon, up to 44.43 g.kg^-1. Understanding the formation of ADE can lead to development of agricultural sustainable management models in tropical low fertility soils.