Thanks to biochar, a mighty soil rich in nutrients and humus has developed in some areas of the Amazon over the centuries. This can also be achieved on European soils. Bruno Glaser, soil biogeochemist and professor at the University of Halle, comes to this conclusion in his article on “The Terra Preta Concept”. However, it is not enough to mix pure charcoal from the DIY store into the soil. Nutrients must also be introduced and the biochar activated. This can best be achieved by composting with biowaste. According to Glaser, for most farmers this means that they have the “ingredients” for an improved soil at their disposal without much additional effort.
What is terra preta and why is it so interesting?
The Amazonian Black Earths (terra preta) were one of the inexplicable wonders of human history until a few years ago. While most of the primeval forest soils are highly infertile, Terra Preta, some of them more than 2000 years old, still has high reserves of nutrients and stable, carbon-rich soil substance. Terra preta is of human origin and is a mixture of human and animal excrements and vegetable waste, some of which have been charred and composted.
The role of biochar
Due to the climatic conditions there is hardly any humus formation in the tropics, whereby soil organisms such as termites, ants, earthworms etc. convert dead leaves and roots step by step into humic substances. Instead, these substances are completely degraded. In terra preta, on the other hand, humus build-up takes place due to the stabilising effect of biochar. Biochar acts as a reservoir for organic carbon (C‑storage is 3 times as high as in neighbouring rainforest soils), nutrients and water. Terra preta contains 2–3 times more nitrogen and 4–5 times more phosphorus than neighbouring rainforest soils. Further positive effects are reduced washout losses and a loosening of soils rich in clay.
Potential of biochar for agriculture
According to Glaser, the comparatively simple production of terra preta allows farmers to upgrade their land, save money on fertiliser and receive credits from emission certificates. The improved soil fertility can in turn lead to higher yields, which will be sufficient to feed the world’s population and satisfy its energy needs (through additional heat and energy production in the production of biochar). In addition, by reducing the carbon dioxide content of the atmosphere, they contribute to saving the world’s climate. Ultimately, this also increases the value of rural areas as they make a substantial contribution to decentralised energy supply.