Terra preta is the mineral-rich, dark soil found in ancient human-created patches of unusually fertile ground in the Amazon Basin.
The name means “black earth” in Portuguese. Terra preta contains abundant charcoal, organic matter, pottery fragments, and nutrients such as phosphorus and calcium. Researchers generally associate its formation with long-term Indigenous management, including the controlled addition of charcoal and household refuse to soils around settlements.
Most heavily weathered tropical soils are acidic and often lose nutrients quickly, so terra preta is unusual. Its charcoal-rich structure can retain water and nutrients for long periods. It is not simply ordinary rainforest soil made dark by natural leaf litter, and the exact production methods varied across locations. Archaeological sites with terra preta show that ancient Amazonian communities altered landscapes substantially without transforming the entire basin into farmland.