[Terrapreta] Terra Preta Trials 2007

[Richard Haard]

On Mar 25, 2007, at 11:50 AM, Kelpie Wilson wrote:

> Here in the Oregon woods, we are constantly clearing small trees  
> and brush around our houses to increase our fire safety. We clear  
> the brush and then make burn piles - spring and fall you will see  
> small burn piles in every back yard. I asked my husband to try to  
> make his burn pile a little cooler to make more charcoal and less  
> ash. After all the small stuff - leaves and small branches - burned  
> up, he misted it with the hose to cool it down and left it  
> smoldering all night. The next day we put the fire out completely  
> with water. We ended up with a nice pile of charcoal for the  
> garden, about 3 wheelbarrow loads of mixed charcoal and ash.
>
> I figure that if nothing else, we are keeping some carbon out of  
> the atmosphere by controlling the burn pile this way - we have to  
> burn anyway.
>
> Does anyone have any tips for how much of this charcoal to put in  
> my garden beds? They are raised beds about 4 feet wide and 20 feet  
> long. How thick a charcoal layer do I need? How deep into the soil  
> should I bury it?
>
> Thanks,
> Kelpie


Hello Kelpie - This is also a study topic for me.

To take advantage of the benefits of charcoal it should be combined  
with fertilizer or compost or manure what ever you are normally using  
in your gardening. You could use as much as 10% to 30 % by volume  
that you work into the root zone with a hoe or fork. If you are  
planting into rows you may apply the charcoal in strips and leave  
other strips untreated, (or bed sections). To see if there is any  
difference.

If your soil is acidic the charcoal and ash will raise the pH. If you  
are concerned about your soil becoming too alkaline you may remove  
the ash before applying.  pH testing is easy to do with  litmus  
papers purchased at your garden store.

Lastly all of us here who are also studying this use of charcoal  
would appreciate if you save a small sample in a mason jar with some  
notes on what you did to make the stuff and what kinds of biomass as  
it may be useful to study the sample at some time in the future.

For your interest here is a clip from a  posting by Larry Williams  
that we sent out to our local friends on the topic.

This may give you some additional ideas on using charcoal and please  
keep us posted on how your garden is growing.

Rich Haard
Bellingham, Washington



My approach in working with the soil is very different from Rich with  
his scientific and agricultural experience. I draw my experience from  
landscaping, wetland restoration, forest ecological workshops and a  
very close tie to nature since childhood. My techniques follow  
Permaculture concepts to a certain degree although I have a strong  
tie to a temperate ecology as it relates to woody debris in the forest.

With Terra Preta, I attempt to view it's usage as I perceive a  
villager would observe it's potential. My meager attempt to make  
charcoal last season was based on city (Bellingham) living with fire  
and smoke restrictions enforced. This means that I made charcoal in a  
Weber grill cooking Alder smoked chicken. A tasty meal with a few  
pieces of charcoal to place in the garden. For the last eight years I  
have cooked on the Weber year round. This translates to three or four  
times a month. So I cumulated a nice little pile, 20 lbs. or so of  
charcoal and charred wood, once I decided to collect the charcoal.

My vegetable bed in Bellingham is layered with composted wood chip,  
leaves, up rooted weeds, grass clippings and sea weed over the  
growing season. The dirt is covered and the soil structure is left as  
undisturbed as possible. I use iron phosphate pellets for slug control.

Yes, I do feel very comfortable with my field experience and do feel  
overwhelmed around strict scientist. Rich has guided me on many  
points based in science that are beyond my schooling and  
observational powers. We have enjoyed each others style for some time  
now. I haven't quite converted him yet though he got excited when he  
photographed the charcoal from under the swiss chard.  He later wrote  
that there was an "abundance of fungal hyphae adhering to the  
charcoal after a relatively short time buried" (four or five months  
later).

I recently did a charcoal (from strawberry guava) pit burn on the  
Kona coast of Hawaii for usage in a garden. The fire was started  
around 10:30 PM. Given that there was more lava rocks than soil I  
needed to smother the fire with green grass, relatively dry coconut  
fronds (leaves) with the petiole laden with moisture and banana  
leaves. This layering was covered with wet cardboard and then covered  
with a light coat of soil. The pile was rained on and hand watered  
till early morning. The fire did break through around 7:30 AM and  
started to burn some charcoal to ash as I put the fire out with a  
hose. I ended up with just over three five gallon buckets of charcoal  
with a quarter of that as charred wood.

What impressed me most was the rich smell of the steamed and charred  
grass (the green additions). I thought of the compost teas made from  
garden weeds which is a different smell and is a very rich soup to  
give to garden plants (this is something that I do in Bellingham). If  
I would have been able to I would have soaked the charcoal (from  
strawberry guava) and charred wood with these greens and then used  
them in the planting beds.

Since I am stateside now a friend will keep me informed on the  
actions taken and if he sees any significant results. I suggested  
that he only do half of any planting row and that he could decide to:
1) bury the charcoal in a new planting bed under 4 or 5 inches of  
soil or
2) mix the charcoal (smaller pieces) in the top 3 inches of the soil or
3) spread the charcoal on the surface and
4) with the charred pieces of wood he could drive the wood into the  
soil (with a hammer if needed) around shrubs. I pointed at some  
pepper plants that could use this technique.

This gives you some idea of how I have decided to use charcoal.


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