The Brasilian Amazon-Fertilizing Low-Fertility Soil

 

DISCOVERIES

Dark and Rich

The Amazon might appear to be lush, but its soil is actually not so fertile.

That’s why the region’s Indigenous peoples have been fertilizing the land to use it for agriculture for thousands of years, according to a new study reported in Science News.

Archaeologists have long come across these mysterious patches of “dark earth” – soil patches that are unusually fertile and richer in carbon and darker in color – at a number of sites across the Amazon River basin. They have wondered whether the Amazonians did it themselves – long before the arrival of Europeans – or if it was a natural geological process.

Now, however, a new study on the Kuikuro people of southeastern Brazil found that they produce a special fertilizer – which they called “eegepe” – using ash, food scraps and controlled burns.

The study also found that the recipe for this ground treatment has been passed down from their ancestors: When a research team collected dark earth samples from around Kuikuro villages and archaeological sites in Brazil’s Xingu River basin, they discovered “striking similarities” between soil samples from the ancient and the modern sites.

But aside from showing that ancient Amazonians have been altering their land for millennia, the study also found that the dark soil can help fight against climate change because it holds more carbon than the other surrounding, untouched earth.

While the specific amount is still yet to be determined, the team indicated that the unique soil might spur more research into techniques to permanently store atmospheric carbon in tropical soils.