Anthropogenic Soil Experiment in Brazil Amazon: Changes in Soil Physical Properties by Organic Residues

Archeological Dark Earths, known in the Brazilian Amazon as Terra Preta de indio are fertile and structured soils considered as a potential model for sustainable agriculture. In order to recreate these soils a field experiment, named New Dark Earth, was set up in 2003 in the municipality of Tailandia, state of Para, northern Brazil. The treatments consisted of the application of organic residues (wastes from local industries) in a loamy sand soil: cattle bones, wood charcoal, shredded wood blades, and the control. The objective of this study was to evaluate the effect of these residues on soil physico-hydrological properties. The results showed that the residues did not significantly increase the soil organic carbon content. Only the wood charcoal resulted in some improvements in soil physico-hydrological properties, such as lower soil bulk density and higher total and microporosity, which was mainly attributed to the high porosity of this material. Consequently, it also presented more available water. For now, it was concluded that despite the three residues are widely available in the region, the use of wood charcoal seems to be the best alternative to bring improvements to the soil physical properties, mainly soil water retention. However, more studies need to be carried out.