making charcoal and testing the results in clay

i think i had started to write this up, but i don't find the draft. so...
first of all some background. the soil i normally use for one garden is mostly clay that i've been reconditioning over the years by growing cosmos and then burying the leftover dried stems and any other remaining organic materials i can find in a long trench. from year to year i keep moving the trench back and forth digging it up and chopping the stems as i shovel. the stems don't fully rot for several years.
this past year after reading about terra preta and biochar i thought i would try to make some charcoal and then use it in areas to see what the effect would be on seed sprouting (and later growth as the season advances) for several species of plants.
first of all i used the worst part (the area with the most clay) of the trench from last season to dig down further into the clay (about 3ft down total). making a space about 10ft long and 3-4ft across. i put all the super dry cosmo stems and other easily burning stuff in the bottom and stomped it down good before taking some dried up shrubs and trimmed off all the small leaves and stems and put that down next with the trunks on top then stomped all this down too.
then to start building a canopy i put some long branches across and other longer pieces of wood and old pallet pieces that we would normally just bury and let the fungi/mushrooms work on. on top of these i put some cardboard and damp earth to seal things up on top. i left both ends open a little so i could get a fire going.
with the wind shifting constantly it was a real PITA. i walked miles around that trench and the smoke kept shifting to follow me. with my lungs it wasn't the best, but the smoke actually was mostly steam coming out.
as the ends burned and dried the covering soil it tended to cave in and self limit the amount of oxygen, but i also wanted to make sure it was getting hot enough to char as much of the materials as possible. using such a primitive thing as a trench, cardboard and dirt i wasn't going to get perfect results. i was curious to see how well it would do anyways. a more controlled setup like a double burner made of metal would probably give better results but that is beyond my current skills to build/operate.
after several hours of steaming and burning i finally buried the largest chunks remaining and called it a day. heavy rains that night and the next day put the trench under water and i was busy for a few days letting it dry out a bit before curiousity and time became available to do a little digging. after a few minutes i could tell there was a lot of change in how the clay and charcoal with plenty of water added was sticking to the shovel. actually, it wasn't. that was an immediate nice thing when it comes to clay. i normally spend a fair amount of time just knocking or scraping the stuff off the shovel. this made digging it all up much easier and faster.
i ended up with about 3cu feet of charcoal and as i was digging it out it mixed somewhat with the baked clay and clay around it. there was standing water at the bottom of the trench so that gives you an idea of how wet it was, but i didn't have much of a sticking mess problem at all. for that reason alone i would consider this a good thing... what it will do longer term we shall see, and if i keep making more and adding it that will also be interesting to see what happens.
with the charcoal/clay mix i made two test areas a few feet long and a little over a foot across separated by normal soil of about the same size and another part on the other side with some extra sand in it. then i ran four lines of different seeds through the whole area crossing the test patches, regular soil and added sand soil. after about a week it appears to not have negatively impacted seed germination for birdsfoot trefoil, alfalfa, green beans or buckwheat. i expected some change because it was so newly burned and it wasn't mellowed at all by adding any compost or aged or anything other than watered.
further through the season i will keep an eye on all of them and see how they do.
i'm unsure what i will do in the future as the burning took a lot of effort. a better means of doing it (covering with metal instead of cardboard) and then sealing it up with dirt would let me fire it, get it going and then leave it alone so i wouldn't have to spend so much time monitoring and fiddling. of course an oven with temperature and oxygen controls would be much better but that's unlikely to happen any time soon here.
the carbon in the charcoal should stick around for many years longer than the stems and sticks otherwise would have so this is a sure soil building tactic. adding compost and green stuff to it and then getting some worms planted into it would certainly make it even better. the charcoal itself will lighten the clay, i've already seen the direct evidence in that from digging it out of the trench.
grinding it up some would probably help too as there are enough larger pieces in there, but i'll let that go for now and let them break down as i spade and turn under materials as i normally would when done with a plot. the stripes of birdsfoot trefoil and alfalfa along the edge will be left alone for a multiyear observation. other than weeded i have no plans to turn or add materials to those plantings other than what grows there itself. unfortunately i didn't have enough material to set aside larger areas to use as controls and test plots or to have more variables to test. some other time perhaps.
i thought for sure that the charcoal and clay mix would be too harsh for worms but as i was smoothing out the areas to get them ready for seeding i did notice several worms in there that seemed ok. it being so wet and the clay probably well buffered or neutralized any harsh chemicals. if it was dryer and there was dry ash i wouldn't have expected to see worms that is for sure.
so it is possible to make charcoal in a low tech way and to sprout seeds in it within a few days. nothing really earth shattering in any of this, but interesting that the effect on clay was immediate. i could see why an ancient rain forest dweller with clay subsoil (as is common in rain forests) would notice it and want to use it for a garden/soil ammendment.
songbird
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Keep up the good work. Your efforts are very interesting.
You may want to invest in a metal trash can. Once the fire is going, throw in the small stuff, and put the lid on the trash can.
Tropical rain forests have laterite soils, not clay. Water absorbs CO2 from the atmosphere, and becomes carbonic acid (H2CO3). The carbonic acid, in turn, disolves metals in the soil, leaving a soil rich in iron and aluminum. The soil is usually very porous and will not hold nutrients (being a rain forest, water retention is not a concern). The classic example is from a book called "The Ugly America". IIRC it concerned a tractor salesman in the 1960s, who was spreading the word about the "Green Revolution" in farming. He plowed a rice paddy as a demonstration, somewhere in South East Asia. When he finished, the rice paddy disappeared, because he had destroyed the lining of the paddy (organic or clay, I don't know), and the water went down the laterite like water down a drain.
Keep us up dated.
--
- Billy

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Billy wrote: ...

it sure beats tv. :)

i suspect there is too much oxygen and opening the lid would introduce more. from what i can tell there has to be heat and lack of oxygen. if i filled the trash can with stuff and then was able to get another fire going in a larger trash barrel like a 55 gallon drum and then set the smaller metal trash can on top of the fire in the drum that might do it, or not, that would be one of the more simple designs.
the question would be about how much fuel i would have to put underneath to bake the contents of the trash can to charcoal. and i probably would need some sort of one-way valve to let off the steam and gasses.
this being a low tech and low budget operation i only have access at present to some flat sheet metal pieces that i can use to lay over the top of a trench. piling dirt around the edges to seal it up and some wet dirt on top to keep the metal cool so that it doesn't warp is about the level of technology here. i almost scored some heating duct tubes from my brother but he forgot i wanted them and took them to the metal recycler. oops.
one other interesting aspect is that by firing the stuff in a trench in the ground any liquids given off that aren't driven off as vapor are absorbed by the soil under and around the trench. i'm not sure if there are much in the way of nutrients in that liquid (i suspect most of it would be water or alcohols, but my reading so far isn't very detailed on the volatile byproducts) but a steel contraption would lose that. it remains an item i'll continue to look into as i get time and rainy days.
i don't have enough new dry materials to do any more test burns until either this fall or next spring. the metal instead of cardboard over the trench will likely be the change i'll make to see if that makes it much easier. i'm not looking to scrounge new organic materials either at this point. too much other stuff going on that needs work or weeding. a few interesting angles are possible with some local enterprises yet it will be a bit before i'll get a chance to explore them. :)

thanks for the correction/information, i knew it was very poor soil (not what you would expect from such a rich canopy overhead) and was surprised to find out that most of the nutrients are quickly recycled or leached away.

never heard of this one before. huh.
similar to the design of terraces and how much a simple change like introducing a different species of worms can destroy the ability of the edge to effectively hold water requiring a change from rice to different crops.

sure thing. :)
songbird
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1491: New Revelations of the Americas Before Columbus by Charles C. Mann <(Amazon.com product link shortened) 32059/ref=sr_1_1?s=books&ie=UTF8&qid96839060&sr=1-1>
p.344 GIFT FROM THE PAST Terra preta exists in two forms: terra preta itself, a black soil thick with pottery, and terra mulata, a lighter dark brown soil with much less pottery. A number of researchers believe that although Indians made both, they deliberately created only the terra mulata. Terra preta was the soil created directly around homes by charcoal kitchen fires and organic refuse of various types.
--
Charcoal isn't particularly high tech to make. Locally, they used to dig
a cave (short tunnel) in the side of a hill. Fill the cave with wood.
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ok, some results appear already.
all of the legumes are growing fine. all rows of them are of the same height.
the buckwheat shows a decline in height of a few inches in the zones where there is charcoal mixed in the soil.
since i am not a chemist and cannot test the soil itself directly i can only guess that the difference is that the charcoal is binding some of the nutrients in the clay.
as a testable hypothesis, eventually i expect the height to even out for the buckwheat and the rest would remain the same (the legumes).
too busy ATM to trim and post the picture... not even sure it turned out until i import it from the camera to the computer. some day.
songbird
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IIRC the soil is supposed to be 20% charcoal for this to work.
--
- Billy

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Billy wrote: ...

i didn't measure the volume as it was made in a trench (in clay) and it was then submerged in water for a few days before i could excavate.
it was mixed with the clay as it was shoveled out of the trench into the test plots next to it and appeared to be roughly 10-30% charcoal, but i couldn't be sure of the exact proportion. enough of it was large chunks that it will take some time before those get broken apart.
to do a measured proportion test plot would take a lot of separation and then remixing. if i were to go that far i'd have to grind it up too. all in good fun if i had an old chipper or meat grinder around to encourage into more decreptitude... but at the moment i see little movement towards such happenings. i'm so far behind in weeding all my extra time is going to keeping the new patches going and getting caught up.
in fun reading lately:
_Long for this World, the strange science of imortality_ by Jonathan Weiner. interesting read, much somewhat familiar to me from general science reading.
i'm looking forwards to gnawing through the resources and reading list in the back on the rainy days.
next up is Darwin's classic _Vegetable Mould and Earth-Worms_. 1888 edition, still in very nice condition. i know i won't look as good at 123 years. :)
songbird
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Billy wrote:

...much snipped but appreciated thanks Billy...

it's being used at the moment. :)

right. if i gradually smash and break up the pieces over the course of a few years then the end is still accomplished. the carbon is largely sequestered and acting as a substrate for all sorts of other interesting things.

coming along slowly. chiropractor is getting me untwisted from last fall's raking. i could go all summer last year hauling tons of materials and have very few back troubles, many hours of digging, etc. a few aches but nothing major. a half hour of raking and i was scrod. finally gave in beginning of June and started seeing if something could help. so far it is helping so we'll see how it continues. cutting into my gardening time though. grr!

o.s.c.a.r. ha, j/k, interesting read. i've moved on to Socrates/Plato for the nonce.

if there weren't worms, fungi, bacteria and mechanical forces they would be quite a pile, but there would be plenty of other stuff too (wood, dead organisms, bones, etc).

it was a quick read, some of it interesting.

my previous readings on this topic leave me no doubt that it's a time-bomb. i have no idea how regulators, government agricultural folks, agricultural scientists at the universities, etc can be so blase' about the whole mess. complacency may do many more us in.

fireflies are going gonzo now here so those are the stars i see.
songbird
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Yoga is good.

If your too careful, you'll miss the humor in them.

It's the usual suspects greed and avarice.

You know that we are stardust? Except for hydrogen, all the other elements were made in stars. It's a marvelous place that we live in. How far away is that star, or that star? How far away determines when you are seeing it, and the further away it is, the faster it is moving away from us. Earth is about 5.7 billion years old, but our kind have only been around about 2 million years (3.50877e-5ths of it's existence.)

I've only seen them once, and it was a magical time.

--
- Billy

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Billy wrote:

...
yeah, and we are perhaps the only critter within vast chunks of space that actually knows this and yet we are still stupid enough to pollute our food, water and shelter.

i wish a movie could do it justice.
years ago when i lived in TN there was talk of fireflies that synchronised their flashes. i never did get to see them.
songbird
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songbird wrote:

Do you have a pH test kit? If the charcoal contains much wood ash it will raise the pH .
D
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David Hare-Scott wrote: ...

no test kit here. many areas are downslope from tons of crushed limestone so high pH is known. when i do a new garden or plant things that are notorious for pH effects i ammend accordingly. so far few bad results.
if i were growing something notoriously finicky i'd pick one up. :)
the charcoal was made in a trench that was submerged shortly after it was burned. when i was digging to examine it right when it was done and as the light was fading it didn't seem to be a lot of ashes. not like what you would get from the bottom of a stove or an open pit. it was good and black in the large part. i remember being pretty happy with the results for it being such a low tech operation.
i was rather surprised that so much sprouted normally only days after the charcoal being burned. i thought for sure that it would be too harsh to sprout or grow much for a spell.
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songbird wrote:
...about making charcoal and testing the results when mixed with clay...
nothing failed to sprout, there was some difference in height of the buckwheat and the green beans, but that didn't make any difference longer term.
by the end of the season it all looked the same height as the surrounding plants that weren't growing in the test strips.
a few days ago a friend dropped off fourteen bags of shredded leaves and i had no place to bury them except the trench i keep going for discarding miscellaneous organic materials (of the non-weedseedy kind). it was about a third full, in they went in layers with dirt.
the back part of this garden is where i'd buried the charcoal and soil mix for testing so that also was excavated and spread into a wider area to benefit the heavy clay soil.
the major improvement is to the texture of the soil. it is much easier to dig, move and the charcoal makes it come off the shovel instead of sticking to it. i'd add it for that reason alone if it harms nothing else.
along with the layers of leaves and soil i turned in some of the green cover crop (mixed perennial legumes) as an added nitrogen source and that along with the roots from the buckwheat will be a great help. next spring, a few weeks before planting, i'll give it another stir to see how it goes.
songbird
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