Biochar is a valuable soil amendment.
What is Biochar?
Florida soil is really bad. Soon after a heavy rain it is dry as a bone. You add fertilizer but it is soon washed down out of the reach of plant roots, or worse it runs off into the waterways. Or you add mulch to preserve moisture and nutrients, keep the roots cooler, and fend off weeds, but before you turn around the mulch has broken down and needs to be replaced.
We don’t have it as bad as the rain forests of the Amazon basin, where conditions can quickly wash away any soil life. Farmers who clear a field using slash and burn may have one good crop (because of the ash–potash from the fire) but over the next year or two, the soil becomes dead and they must move on to the next part of the forest. But there’s a better way. It was known to the ancient people of the area, but they were wiped out by disease brought by European explorers centuries ago. Only recently have their secrets been re-discovered. There are areas of the rain forest that contain deep rich black soil that is tremendously fertile even after hundreds of years. It turns out these fertile areas were man made. [BBC documentary “The Secret of Eldorado” 1 hour]
The secret? Terra preta, “black earth” in Portuguese. What’s the difference between Terra preta and typical dead soil? Charcoal. Slash and burn creates polluting smoke and soot but leaves nothing behind but a cleared field and some ash. What the ancient Amazon people did might be called slash and char. They still cleared the field, and still burned the plant material but did so in a closed pit that kept out oxygen. They were left with charcoal. Today we call it biochar, or charcoal created and used as a soil amendment.