Amerindian Anthrosols: Amazonian Dark Earth Formation in the Upper Xingu

Amazonia is a region known for large expanses of acid, infertile soils difficult to farm without considerable inputs of fertilizer or long fallow periods. In this same region, scattered patches of fertile black soil also exist that are highly sought after by farmers for planting nutrient-demanding crops. These areas are the result of the activities of prehistoric Amerindians. We know that the black earth is associated with archaeological sites and is, in itself, an archaeological remain that is full of information about past societies and their resource use. Scientists also believe that research on black earth, known as terra preta de índio in Brazil, could lead to a better understanding of soils and their management, particularly nutrient-poor tropical soils. Questions remain as to what processes were in action to produce the fertile black soil and what keeps them fertile over long time periods.

The Kuikuro Amerindian word for the black soil is igepe, which is also their word for cornfield. They plant fields of their staple crop manioc on the normal red soils but all other crops are planted on patches of deep terra preta with abundant ceramic fragments and boasting large prehistoric earthworks that give structure to the sites. They plant banana, corn, squash, sweet potato, papaya, sugarcane, and many other crops that generally would not do well in the natural red soil. The fact that they are willing to travel up to 10 km or more to reach these igepe gardens and haul the produce back to the village demonstrates the value of the terra preta to the Kuikuro. They are using a resource that was accumulated over decades or centuries by previous inhabitants but, are they also creating it themselves?