I have some friends who offer a Bread CSA. (CSA stands for Community Supported Agriculture.) Folks sign up to buy so many loaves a week for 3 months, pay in advance, and then enjoy receiving yummy bread deliveries each week. My friends grow some of the grains and all of the specialty ingredients – think sunflower and poppy seeds – that go into their breads. They bake them in a special, wood-fired oven and produce dozens of tasty loaves each week. A by-product of the whole process is a 55 gallon drum of charcoal every few months. That’s a 55 gallon drum of black gold for the soil.
Farmers and researchers in the jungles of South America first discovered the amazing effects of charcoal on soils about 200 years ago with the discovery of the “Indian Black Earths”, now known as Terra Preta. These are soils that are especially fertile and stable, remaining productive over longer periods and requiring shorter rest periods than the majority of soils in the region. Jungle soils are notoriously low in fertility. Almost all the nutrients in a jungle system are held in the living biomass, so catching and cycling the nutrients before they leach out of the system can be tricky. To have a system that catches and holds nutrients in the soil is almost miraculous. The photo below shows the difference charcoal can make.
Investigations in the last 20 years have led to the general conclusion that humans were largely responsible for creating these terra preta soils over a period of several thousand years. By digging pits or trenches, filling them with biomass, setting it all on fire, and then smothering the fire with soil, the people of these jungles created areas where the soils have a very high charcoal content, called biochar. These soils can support microorganisms and, therefore, hold nutrients and fertility. Best of all the carbon in these soils is very stable, often lasting for thousands of years.
This is a wonderful example of humans enhancing an ecosystem and creating a legacy that benefits that system even to this day. Who were these people? What was their society like? How did they come up with the biochar idea? If there are authentic answers to these questions, I am unaware of them.
My husband and I are happy to receive some of the charcoal largess produced by our bread-baking friends. We started hauling some home about 2 years ago. Most of the initial barrels went around a young walnut tree along with sizable amounts of used goat and cow bedding. Last fall, at only 6-years-old, our walnut gifted us with its first crop, almost a gallon – after shelling – of delicious nuts. I don’t know if the biochar had anything to do with the early fruiting, but I’m sure it helped with the high quality of the nuts.
This spring I’m also experimenting with adding crushed charcoal to my soil mix for seedlings, following a tip from our friend Eric who swears it enhanced the growth of his veggie starts quite noticeably. On Monday I pricked out some Komatsuna seedlings and set them up as my “official” experiment. Half got the charcoal in the soil, half did not. I’ll keep you posted on their progress.
If anyone out there has experimented with charcoal in soils or seed mixes, let me know what you discovered!
Link to Cornell University’s page on Terra Preta.