Terra Preta – Agriculture’s Saviour

Terra preta or black earth found in the Amazonian basin has been mystifying scientists for the last hundred years. Originally thought to have occurred naturally from volcanic deposits this has been dismissed in favour of an anthropogenic source. Patches of this immensely rich soil up to two metres deep and up to several hundred hectares in area have been located in what would have been suitable settlement areas along the great river and are scattered with pottery shards to substantiate this theory.It has three times the standard nitrogen and phosphorous and twenty times that of carbon compared to the surrounding rainforest soil which is poor in nutrients, much of it being leached by the immense vegetation.  Recent studies would suggest that these so called primitive people knew of a way to slash and smoulder which locked in the decomposing vegetation transforming it into biochar as opposed to our slash and burn techniques which escapes into the atmosphere. Instead some 50% of the carbon returns to the earth thus creating a longterm carbon sink effect and reducing carbon dioxide emissions. Not only are the nutrients locked into the soil for thousands of years but, it is actually self-generating at a rate of about one centimetre per year. The value of this as a rich compost is obvious as crop yields at least double or triple, but far more interesting for the sustainable future of the planet and how to feed 9 billion is how to replicate this amazing secret of our ancient farmers for an ecological approach to modern agriculture.Furthermore, scientists from Cornell University suggest that 12% of human derived carbon emissions could be offset by introducing this biochar technique.