Get The Dirt on Terra Preta
What’s Terra Preta, you ask? Well it’s dirt, or soil to be more accurate, and it is amongst the most fertile of soils on Earth. The odd thing is, it is found primarily in Brazil, and to a lesser extent in other South American countries.
Tropical rain-forest soils are typically fairly poor, because the frequent rains wash nutrients out. They get plenty of organic material from the jungle canopy, but as fast as those organics break down the beneficial chemical compounds are washed into rivers brown with dissolved organics and minerals.
Slash and burn agriculture is used to clear land for agriculture, but such exposed soils wear-out within a few years and the farmers move on to expose new plots, at the expense of the forest. But it hasn’t always been that way.
Apparently the Native South Americans of about 500 B.C. found a way to enrich their soil and keep those organic nutrients from washing away. There is some argument whether they intentionally enriched the soil, or it was an accidental by-product of their lifestyle. Knowing how observant pre-industrialized humans tended to be, I think the rich soils probably began as a by-product of their lifestyle, but was soon noticed (i.e. ‘discovered’), and expanded intentionally.
So what is the secret to these amazingly rich soils that remain fertile to this day — hundreds of years after they were abandoned by their original tenants? In a word, charcoal. Not the big chunks in your grill, but fine powdery charcoal dust. The charcoal itself does not add nutrients to the soil, and is in fact almost inert — taking thousands of years to break-down into its chemical constituents. But the carbonized organics facilitate chemical reactions (high cation exchange capacity), and harbor beneficial bacteria, retain moisture, improve soil texture, and may have other, as yet unrecognized, beneficial effects on the soil.
As if all that weren’t enough, if modern agriculturists adopt biological charcoal (Biochar) as a soil enhancement, it may help save the environment and reduce global warming! In the tropics, artificial Terra Preta could help replace slash and burn agriculture with a more sustainable and more productive alternative, saving the rain forest. Meanwhile, use of Biochar anywhere would contribute to the ‘carbon sequestration’ method of reducing atmospheric carbon — helping to slow global warming. Soils that retain their nutrients better will also need less fertilizer, leading to cleaner rivers and lakes, since the main water pollutant in many areas is agricultural run-off. This stuff is near-miraculous, and dirt cheap!