In the 1870s, scientists exploring Amazonia in South America made an unusual discovery. Working independently, James Orton, Charles, Harti, and Herbert Smith described patches of black or dark brown soils, varying in size from 5 to more than 300 hectares, within a landscape otherwise typified by highly weathered reddish or bleached soils.
A detailed report from Smith, a geologist, characterized these “dark earths in Amazonia” as having a top-layer of a fine, dark loam, up to 60 centimeters thick. He also described them as the best soils of the Amazon, producing much higher crop yields than surrounding soils, and speculated that they owed their fertility “to the refuse of a thousand kitchens for maybe a thousand years.” That they were human-made was indicated by the abundance of fragments of Indian pottery that “cover the ground… like shells on a surf-washed beach.”
Despite the unusual nature of these findings, they initially failed to excite many scientists. Almost a century later, however, Wim Sombroek, a renowned Dutch soil scientist, sparked international interest by including several pages on the “terra preta” (black soil) and “terra mulata” (brown soil) in his influential 1966 book on Amazon soils.