The black earth Terra Preta is said to have many positive properties: healthy plant growth, good crop yields and reduced susceptibility to pests and diseases. Johann Fritz explains where Terra Preta originally comes from and what makes the black earth so special.

Terra Preta: Miracle soil from the rainforest

In 1878, researchers first reported on deep black soils in areas along the Amazon, which were clearly different from the infertile, light-colored soils that were common there. Seven years later, the first record appeared with descriptions of the ingredients of these black soils, in which pottery shards, remains of charcoal and stone tools had been found.

Its extraordinary fertility was documented in 1903, but it was not until 1966 and the 1980s that intensive research made it known worldwide – the soil that the locals call “Terra Preta do Indio” (Portuguese for “black soil of the Indians”). Measurements showed that it has a humus content of at least 15 percent and is well over a meter thick in some places.

We now know that these Terra Preta soils were created by an advanced Indian culture that perished around 500 years ago, soon after the arrival of the European conquerors. And that the assumption that only a few people could have lived in the Amazon basin due to the poor soil (today there are around 350,000 inhabitants) is wrong: in fact, 5 to 25 million people lived here in large cities along the Amazon and its tributaries, as evidenced by finds of settlement remains – and as was also reported by the first Spanish explorer Francisco de Orellana (1511-1546), whose records were dismissed as figments of his imagination after his return to Spain.

However, such a large number of people could hardly have lived in an environment with less fertile soil. The reason for the once high population numbers can therefore only be the Terra Preta.

Production of Terra Preta: A 7,000-year-old method

In the search for the secret to the fertility of these soils, it turned out that the two most important factors in the formation of Terra Preta are charcoal and organic waste. The former inhabitants had buried all their organic waste, together with the charcoal that was created during cooking, in the soil – sometimes in large clay pots – or burned or charred it above ground in compost heaps.

In this way, the Indians not only solved their waste problem, which posed a constant health risk in the humid, hot climate of the Amazon, in a very simple and efficient way, but also used this process to keep the water clean, which was just as important for their survival as fertile soil.

By burying the waste, it was not simply composted, but fermented in an airtight manner, and then gradually turned into soil and turned into Terra Preta. This formed the basis for a sophisticated multi-level cultivation system that allowed sufficient food to be produced. In this way, the Indians operated a recycling economy with almost no losses – and this was already a good 7,000 years ago, as finds clearly show.

Sustainability

Another surprise was the regenerative power of the Terra Preta soils, whose enormous fertility has remained unchanged up to the present day. It still enables the locals to harvest several crops a year – without additional fertilizer. In another astonishing phenomenon: if you remove a large layer of Terra Preta soil, it will regain its former thickness after several years without any outside intervention. These findings promted intensive research into whether and how the Terra Preta system can be transferred to our climate and soil conditions.

Terra Preta as plant soil in modern times

In the meantime, numerous applications have shown that black earth produced according to the principles of Terra Preta is also very well suited to building up the soil sustainably and without additional fertilizers and to supply it with all nutrients, or to revitalize depleted soils or bring over-fertilized soils back into balance.

Initially, however, attempts were made to patent the new Terra Preta method in order to capitalize on it. But a cultivation technique such as the one given to us by the Indians should not and cannot “belong” to anyone. Fortunately, knowledge of black earth has now spread worldwide, as it is needed more urgently than ever.

Further reading:
https://www.amazon.com/s?k=terra+preta+soil+book