Anyone adding charcoal to their hugelkultur beds? I have been reading about the areas in the amazon where the indigenous folks were using charcoal or bio-char along with large quantities of organic matter to improve the quality of their soil. If you google Terra preta, there is quite a bit of promising information out there. I have just started a bed to see how it work in my area. My next bed with be a more conventional hugelkultur bed.

Bill, last year we had a discussion about bio-char at my "Power and Energy" cubit (now pretty much inactive). Carol (Aloha Hoya - and her Wizard) know about the advantages to adding this to garden soils. Also, Lyle (in daylily discussion here at ATP) has up close and personal experience with adding bio-char to his soil with huge success.

http://cubits.org/EnergyAndPow...

I started using charcoal on a large scale when I was living in Central Arnhemland in sand that seemed bottomless. The soil was acidic, never retained moisture, was leached of nutrients, and with the climate and watering, any organic matter broke down rapidly and leached away. Of course if you stopped the watering to preserve the organic content, then your plants would suffer and die. It had the makings of a no win situation.

But there was a large amount of ash available from the seasonal fires. So I shovelled it up by the trailer load and brought it into the gardens. Made a world of difference. From the worst of all worlds it became the best of all worlds. Sand drains well, is easy to dig, plant roots penetrate deeply without effort, etc. The charcoal absorbed nutrients and moisture making them available to the plants over a long period. Microorganisms found shelter and sustenance in the charcoal. And when the warm climate made the organic matter and humus run short, the charcoal being inert and insoluble was always still there holding its abundance.

Well, if I seem a bit biased towards charcoal, it because I so very much am. It's a bit scary when I look back on those early days, they were in the early 1990's, last century!!!!

Terra preta is still a bit of a contentious issue, there are some who still claim it's a naturally occuring soil rather than anthropomorphic. They say it's usually found near rivers where floods could accumulate charcoal and that people only took advantage of it. But no one disputes that it's the best soil you can have. One of the things with Terra preta is that the charcoal is finely ground. From memory, I think the grains were no more than 0.3 millimetres. It becomes a tedious job to achieve that for a large scale garden. What I did was to use a concrete mixer with a few largish rounded lumps of quartz and an old towel covering the opening to prevent the dust from escaping. I made quite a lot of fine charcoal like that. Used it both in garden beds and potting mixes. You just have to watch out for the residual white ash in it raising the pH too high. Done through composting is much better if you have the time.

Charcoal/Carbon, where would we be without it?

Terra Preta (black earth soils) are a byproduct of swidden (slash and burn, juhm) horticulture. Juhm farming or slash and burn is a type of indegenous farming used to farm tropical forest soils which tend to be thin and nonfertile. The indigenous practice was to clear plots by burning and then planting certain crops amongst the burned stumps -- so this was incorporating the fertility of burned wood in different stages -- including charcoal into the soil. The result is a soil more suitable for farming, but also an ecological situation where fields in various stages of regrowth were maintained by the land owners. So there was not only farm land, but also other fields in various stages of being returned to a forested condition. And variability in stages of regrowth also provided forage for animals -- thus creating a much more complex ecology than would have existed without the intervention of the human farmers.

It was a way of making a not so productive environment very productive and sustainable --- if the amount of land required was available for the human population.

Slash and burn horticulture has gotten a bad rap -- mostly because outsiders have viewed its failure under extreme population pressure and attempts to continue the traditional practice on restricted acerage.

The charcoal contained in terra preta soils of South America are just one remnant of a highly productive slash and burn horticure economy.
Here is one description of the practice: http://www.eoearth.org/article...

Hazelnut, thanks for that link. I remember the slash and burn farming from anthropology studies. However many proponents of an anthropomorphic origin of Terra preta suggest charcoal was brought in to the gardens, others that vegetation was brought in and burned on site. Another suggestion was that the charcoal was produced by the deliberate slow burning of vegetation under soil. With low oxygen you get more charcoal. And some say that they went to the extent of making activated charcoal which was then added. Because the practice ended after the European invasion of the areas no one actually knows for sure. The thing with slash and burn was that it always had a time limit with soil fertility. Terra preta is "self renewing". And is also quite deep, more so than what slash and burn would produce.

There's a system in India still current where they use similar methods and add organic household rubbish. Then each year the smash all their clay cooking pots and add them to the garden. They never use their pots more than one year.

When I was in Papua New Guinea I saw a lot gardens out in the remote areas that were at different stages, from new to abandoned. Food was still gathered from the abandoned ones as some plants persisted for quite a while. But you could see the jungle moving back in on them. Even though abandoned, the soil in those gardens looked a thousand fold better than the soil at my place. Would have loved to have swapped some of theirs for mine.

A garden in PNG recently cleared and planted up with Taro.


An abandoned garden being taken over by Bananas and Choko before the forest moves in.

TropicBreeze. Yes. As you mentioned slash-and-burn creates a mosaic of different fields at different stages of returning from human cultivation back to wild re-growth within an ecosystems. I think some of these use a 20 year cycle or more, but under population pressure are forced to re-cycle less land more often.

Im not really sure if terra preta soils are simply successful slash-and-burn or if there is something different going on there. But it is true, that ethnographic practice of slash-and-burn is considered to be temporary, not permanent. At the same time it creates a complex man land relationship in that there are different fields at different stages of regrowth at any given time. This means more food resources are available not only to the human community, but to game animals as well. Lots more for the dinner table.