Terra preta – Amazonian soil
I’ve just watched a fascinating TV program syndicated to Australia by the BBC on the ‘search for El-Dorado’ in the Amazon rainforest. Following Spanish explorer tales, the progam described how the myths of a large civilisation were debunked on the strength of soil fertility – or lack thereof. Rainforests may look fertile, but the amount of rainfall means that nutients are quickly leached from the soil leaving infertile clay substrates. We have a similar problem in Australia – since most of our land mass was once sea bed and hence below a thin layer of sandy top soil we have a layer of salt – which through over-cropping of the soil, quickly rises to the surface, causing ever increasing desertification of our farmlands.
Enter some persistent researchers who allow their curiosity to be drawn to seeming ‘islands’ of rainforest in otherwise barrren land. It turns out that beneath these fertile islands is a huge legacy of pottery shards – of pots that would be far too large for nomadic people scattered thinly across the landscape. The secret? The black soil – which appears to be artificial. Amazonian small-croppers, like those in Malaysia and Indonesia, clear land by slashing and burning. But by burning on the surface, all the nutrients get burnt to ash leaving only a small amount of added fertility value for farming. The difference appears to be that the Amazonian people of the past also felled trees and burnt the vegetation, but they did so by covering it with earth and producing, not ash, but charcoal. Charcoal is highly absorbant and would retain nutrients in the soil. As one researcher has noted, terra preta soil (black soil) enriched with mineral fertiliser gave 880 percent more yield than the same substrate enriched with the fertiliser alone. In other words the fertiliser was not being leached form the soil.
Now, if only we in Australia could apply that kind of process to our own soil – how much more productive could our land be?
Cheers
Jerry
Comment by Khim
Dear Jerry:
I also saw this same show. Although, we didn’t get the BBC in our Cable TV package until early this year 🙁 Living in North Dakota is a bit like living in the Bush 🙂
One has to wonder what kind of human, who after slashing and burning through the rain forest for farm land that only stays fertile for a year or more, would think that slashing and burning some more of the forest is going to somehow uncover more fertile soil ::blink:: The Brazilian government clearly isn’t doing enough to stop this nor create alternatives for these people who depend on agriculture to feed their families and provide income.
Unlocking the secrets of Terra Preta could change all of this and, hopefully, allow the damaged rain forest to rejuvinate itself. In the meantime, if more farmers in and around the rainforests could be educated to use charcoal as fertilizer in the already burned land, there would be less need to continue destroying more forest for farmland.
I really appreciated your comments on the topic of Terra Preta and also your comments regarding the comparison of the problems that exist in Australia as well.
We here in the US also face similar problems which go unheeded by the Coporation. They figure it is the next generations problem…. they are so blind.
Khim
Posted on December 11, 2005 at 4:08 am