Make charcoal directly in garden bed?

So, I'm thinking of trying this out to make a new garden area.  My thought is to dig a trench some length, say, 12' long, 3 or 4' wide and a couple feet deep.  I would pile the existing earth to the sides, so the trench would be somewhat deeper, and then make charcoal in that trench.  Once the charcoal was completed, mix unfinished compost (just dump on the greens and browns) with the original soil and bury the charcoal.  After that I could use my broad fork and do a couple passes just to mix everything together better.  Then I could move over a few feet to leave a path, and repeat the process.  It would be some work up front, but I'm thinking the "mix" will just compost itself and inoculate the charcoal and everything will be ready to plant in next spring.  We can't plant here until pretty late, so the garden area will get a couple months time to develop more in the spring in addition to the time it has to work this fall.

Any thoughts?

Forgot to mention, I top all my beds with a thick layer of woodchips whenever possible, so I would probably do that here as well.

My first thought is to worry about firing the clay particles solid around edge of the trench, hindering root-access. I used to have a place where I pit-fired ceramics and it took several years for it to really over-grow when I was done with it. But that was after eight or ten firings, not just one event. It's an intriguing idea, but maybe start small.

Christopher Weeks wrote:My first thought is to worry about firing the clay particles solid around edge of the trench, hindering root-access. I used to have a place where I pit-fired ceramics and it took several years for it to really over-grow when I was done with it. But that was after eight or ten firings, not just one event. It's an intriguing idea, but maybe start small.

That's a really good point I hadn't thought of.  I have quite a bit of clay, I would hate to create a bath tub effect.  I would probably need to use the broadfork to break up the sides.  It may not be worth it in the long run to do it this way, because I'm not sure how well the fork would break up the fired clay pieces.

The spot that was used to burn the excess building material from my house has never grown anything.  I can't remember when the house was built.  We bought it in May 2013, and the house might have been three years old then.

Croton has taken over that area this year though still not over the burn spot. Though, who knows what might have been burned though I assume only juniper and pine wood. No drywall as the house was just a shell with no interior finishing.

If this was a multi-year approach, I'd say go for it. But to plant next spring? I'm concerned that it may backfire.

Will that heat sterilize the subsoil or the ash make it uninhabitable for friendly soil biota? Will burning in situ create high pH issues or hardened layers?

Raw char, in volume, is not instantly plant friendly. It needs to be integrated into a soil matrix, and needs time to soak up nutrients, host friendly creatures, and become part of the mechanism.

My 2c -- I'm just speculating based on my local situation. A lot of this depends on your local conditions, so there's no single answer.

Douglas Alpenstock wrote:If this was a multi-year approach, I'd say go for it. But to plant next spring? I'm concerned that it may backfire.

Will that heat sterilize the subsoil or the ash make it uninhabitable for friendly soil biota? Will burning in situ create high pH issues or hardened layers?

Raw char, in volume, is not instantly plant friendly. It needs to be integrated into a soil matrix, and needs time to soak up nutrients, host friendly creatures, and become part of the mechanism.

My 2c -- I'm just speculating based on my local situation. A lot of this depends on your local conditions, so there's no single answer.

Some of that echoes my thinking as well. If it doesn't work well for a year or two, I don't really care. If I create a problem that lasts five years or more, it still isn't a big deal, but in that case, it certainly wasn't a good idea. I have enough garden space that I can grow far more than I need, but no point wasting time and energy on something that has no reasonable return. I know I can get results mixing charcoal into my compost until it's well inoculated and then applying it. If this method doesn't give any gain greater than that, there isn't any reason to do it.

Really, though, all the potentially negative effects are short term. With time and a bit of smart management on your part, natural systems will move in and take over, like they always do.

I believe the guy behind SkillCult does this with good results.

William Bronson wrote:I believe the guy behind SkillCult does this with good results.

I would appreciate a link, because I suspect it's possible.

Thinking it over, if you mix in enough active biostuff into the char in the trench, in the subsoil, it could be some sort of terra preta / double dig hybrid. And then you layer on the "cake" of topsoil and the "icing" of mulch. Hmm.

Hey,

Firstly Love the inventive passion!

I have some thoughts,

First step is why would it be beneficial to do so,
Labour efficiency.
Reduce waste.
Could burn weeds.

Problems!
moisture in the ground
Killing organisms in the soil
removing organic mater
potential bonding of fine particle soil
potential creation of hard pan layer
charcoal acting as a sponge
Air flow through the system

Although it would properly be better to make the charcoal not in the ground.
I am interested in working out how to do so because it may bring about new knowledge and ideas!


So first of all dig the hole right. 2 ft deep.
then dig tunnels leading into the hole.
about 4 inches in diameter will be fine.

have the sides of the hole mounded with the dug out soil like a big donut.


then put weeds if you have them on the bottom of the hole. then put green sticks around the sides and an 2 inches deep off the bottom,
then add aggregates, 1/2 an inch to 3 inches in size, make a layer 2 to 4 inch's deep,  then add the wood and accelerant burn it wait till it cools down. add agge pipes into an air tunnel. watering fertiliser hole now!

smash up.
Now add inoculants,
now add a few sticks to create aeration.
now add aged manure.
now add Lucerne or straw or leaves,
blood and bone.
now add soil from above mix a bit.
add worms.
add compost,
add soil
add mulch.
water with respect.
let rest for 2 weeks.

Now plant!



Hope this helps some how!

Stack woody waste in a shallow trench in a garden bed; burn the brush until the smoke thins; dampen the fire with a one-inch dirt cover; let the brush smoulder until it is burned.

Douglas Alpenstock wrote:

William Bronson wrote:I believe the guy behind SkillCult does this with good results.

I would appreciate a link, because I suspect it's possible.

Thinking it over, if you mix in enough active biostuff into the char in the trench, in the subsoil, it could be some sort of terra preta / double dig hybrid. And then you layer on the "cake" of topsoil and the "icing" of mulch. Hmm.

I went looking for it, no such luck.
I think David the Good did the same , for his pumpkins, I'll see if I can find that.

Mark Van wrote:Stack woody waste in a shallow trench in a garden bed; burn the brush until the smoke thins; dampen the fire with a one-inch dirt cover; let the brush smoulder until it is burned.

A lot of us do not leave a fire or bed of coals unattended, ever, for excellent reasons. First, extreme fire hazard; second, respect for anyone less than a mile downwind.

I recall, from my youth, driving through stinking long-wet-smouldering fires from brush piles after clearing land with bulldozers. I don't recall reports of armed interventions by close neighbours, but frankly no jury would convict. Just a thought to ponder.

I have done this with no negative results, although I only did one burn in each spot and tilled afterwards to break up the soil.

I now have an above ground "trench" that fulfills the same role without cooking the soil, beyond the top inch indirectly. it is an oil drum cut down it's centre line from top to bottom, and just used laying on its side. the drum fills with char as you keep adding more fuel. When done, just fill it with water and leave it to sit for a few days.

half a drum is easily portable to where you need it.

I think it's a good experiment.  I would probably broadfork it afterwards. you may get a sense of if you have created a clay bathtub wall, and ensure that the soil is broken up underneath.   Also I wouldn't put wood chips on top, which will need nitrogen. I would add your own nitrogen in terms of kitchen compost, worm compost and use it as your place to take a wiz.

John S
PDX OR