This Ancient Soil Practice Holds a Key to Our Future, and Our Past

In Brazil’s Amazon basin 2,000 years ago, people farmed on some of the most fertile soil in the world. Fed by the bounty of this soil, the people built a complex society and large cities. And they did it all fueled by crops sown in soil they created themselves. This agrarian lifestyle continued until the 1500s. Then the Europeans invaded, history happened, and it all disappeared. The fertile Terra Preta soil went untilled for hundreds of years. 

Early discovery

In the 1540s, the shores of the Amazon river looked far different than they do today. Francisco de Orellano, a Spanish explorer, described seeing large cities, glistening white, with roads stretching inland and soil as fertile as Spain. He was witnessing the last days of a grand society built on rich, fertile, black soil known as Terra Preta. As Europeans invaded, the cities and fields were abandoned. 

The secrets of the fertile soil remained hidden until the late 1800s, when Charles Hartt first described this man-made soil.

What, exactly, is Terra Preta, and why does it matter? Let’s find out.

The Backstory

Terra Preta, which translates from Portuguese as literally “black soil,” is a combination of low-fertility soil with bone, pottery, manure, compost, and a high-carbon charcoal called biochar. The resulting soil is incredibly fertile. Researchers are still trying to figure out to what extent farmers from millennia ago engineered the soil, while modern-day soil scientists are working to recreate Terra Preta for use in other regions. 

Current Research

Today, soil scientists are working on synthetic Terra Preta, or STP, which is a fertilizer based on the elements of the original soil, including blood and bone meal, crushed clay, manure, and biochar. This fertilizer, when added to soil, transforms it into a nutrient-rich mixture capable of sustaining crops.

The production of biochar has been a topic of intense focus, resulting in production methods to create biochar from organic materials. 

Why It’s Important

Biochar production recycles forestry and agricultural waste, and when done in a particular way, the process is an energy source with biochar as a byproduct. While this energy production is an added benefit, the real value lies in the ability of synthetic Terra Preta to improve the soil it’s added to. 

In an area like the Amazon, where soil fertility is sometimes unpredictable, this is especially important. In fact, Terra Preta is also changing our understanding of life in the Amazon basin throughout history. Although it was previously thought that soil conditions were too poor for agricultural operations that could sustain massive populations, the existence of Terra Preta proves that isn’t the case.

The future of sustainable agriculture lies, in part, in the soil of the past, as we relearn, through a scientific lens, what the Amazonian farmers of 2,000 years ago knew so well.