The Rescue of an Old Indigenous Practice in the Tropics - Using Charcoal to Improve Soil Quality.
Wenceslau G. Teixeira1, Gilvan C. Martins1, Murilo R. Arruda1, and Christoph Steiner2. (1) Embrapa Amaz˘nia Ocidental, Rod. AM 010 - Km 29 - Manaus - AM - CP 319 - 69011-970, Manaus, Brazil, (2) 1 Institute of Soil Science, Univ of Bayreuth, Bayreuth, 95440, Germany
Studies have shown that anthropogenic soil horizons modified by Amerindian populations, known as Terra Preta de ═ndio (TPI) also known as Amazonian Dark Earths are found in patches throughout the Brazilian Amazon. Terra Preta de ═ndio normally show plaggic, terric or hortic horizons. These horizons are identified by dark matrix colors of the top horizons, and the presence of ceramics and charcoal pieces. The top horizons on TPI sites show some differences on soil chemical, physical and hydraulic properties compared to the adjacent soils. The top horizons typically show high amounts of phosphorus, calcium and magnesium relative to the surrounding soils. The high levels of soil organic matter and black carbon strongly darken the color, change the structure, and the hydraulic properties of the soils. The texture is lighter and the workability of TPI is easier, especially when TPI is wet. Because of their easy workability and longer lasting fertility in relation to surrounding soils, local populations intensively cultivate these sites. TPI seem to be a very resilient soil type that keeps their good soil physical qualities even when submitted to intensive soil management. Frequent findings of charcoal and highly aromatic humic substances suggest that residues of incomplete combustion of organic material are important. In weathered tropical soils, the persistence of organic matter plays a key role in maintaining soil quality (good fertility and favorable physical conditions to crop production). In Manaus, Brazil we are studying the effect of charcoal amendments to the dystrofic and acric soils in an attempt to recreate some soil qualities showed by the TPI. We are also examining the possibility of using a new agricultural praxis, called - slash and char - as alternative to the traditional slash and burn. In this presentation we show some results from investigations concerning a better characterization and expansion of the knowledge of TPI sites in the Brazilian Amazon. Moreover the approach to reproduce some qualities of TPI using charcoal residues are also reviewed and discussed.