Terra Preta do Indio
Terra Preta do Indio
Four years ago, I bought a book called “1491”. I have always been interested in history and the American Indians (Amerinds). The book was all about what the Americas were like before Columbus. It was full of all kind of information I was not aware of. One of the most interesting chapters was about the Amazon Basin.
I knew about the difficulty of farming in the Amazon jungles. The only thing that keeps nutrients in the soil is the rapid recycling that takes place. As soon as something dies, its nutrients are immediately captured up by some other life form. If an area is cleared for farming, you can only grow crops on it for about 3 years, then the soil becomes infertile, as all the nutrients are drained from the soil by the heavy rain. The soil, pounded by the rain, ends up with the consistency of a brick.
I knew that the only kind of farming that took place there was “slash and burn”. The people would cut down all the trees in a small area, burn the debris, plant crops, harvest, then have to move on to do the same thing over somewhere else. This slash and burn can not support a huge population, and it was believed that this was how it had always been.
When the historical writings of the first Spanish explorers to go down a few of the rivers there, were recently re-read it was discovered that they had reported very large settlements along the river The Spanish couldn’t investigate, because they were being constantly attacked by the inhabitants. In recent times, archeologists and soil scientists began “digging” around in the Amazon basin and found some amazing things.
They found areas, where crops were grown, year after year, and were still fertile. When they dug into the soil they found that instead of the reddish color typical of the jungle, it was very dark, and full of pottery chards. The darkness was due to charcoal. They called this soil “Terra preta do Indio”, because it was not natural, it had been made by the amerinds.
Charcoal, does not generally made by nature. When wood is burning good, it has to be smothered over to starve it of oxygen. The wood continues to burn, but without the oxygen, the combustion is not complete, and it leaves most of the carbon locked in the resulting charcoal. It was discovered that the charcoal left in the soil captures the soil nutrients. Organic matter “sticks” to charcoal and is not washed away with the rain. Charcoal can hold carbon for up to 50,000 years. I never did discover what purpose the potsherds fulfilled, but in some plots there were millions of them.
The Amazon basin amerinds figured out, that instead of slash and burn, if they would “slash and charcoal” then put that into the soil, with all the organic waste that they had, then they could farm an area over and over. Experts estimate that somewhere between .1% and 10% of the Amazon basin had received this treatment. Plots typically were between 5-15 acres, with terra peta soil between 2 and 6 feet deep. The soil is still very productive. Somewhere down through history, the knowledge was lost, but new interest has been sparked.
Storing carbon as charcoal not only keeps it out of the atmosphere, but it also really helps keep nutrients, that are generally lost, in the soil. Seeing a show about humus the other day, that mentioned this in terms of modern recycling research in Europe, made me interested again in the subject. Instead of calling charcoal “charcoal”, they have now re-branded it “bio-char”, but its still the same stuff.
Last week when I went to Prince George, I bought a bag of charcoal briquettes made for barbecue grills, brought it home, and smashed it into small chunks with a hammer. I spread the chunks onto part of my garden, (see photo), as part of a fun experiment to see if I could see any difference in growth. I read that there wasn’t much difference in the first year, but the second year there should be improvement. I don’t expect miracles, I did it mostly out of curiosity, and an admiration for amerind agricultural technology, and if nothing else, it will help the snow melt quicker.
Tuesday, March 27, 2012