Dumping Charcoal in my Garden

Dumping Charcoal in my Garden

Last year, I planted a small section of my yard with squash, and it was going great, until one day I looked at it and saw a frightful mess: the squash stalks were all smooshed, the leaves were turning brown and it smelled bad.

For several years, I had grown tomatoes in the same spot, with very marginal success.

I concluded, with no scientific basis or anything to go on except what counts for me as intuition, that maybe the ground was sick.

Late last fall, I smoked some meat and had a grill going simultaneously, so we had a lot of charcoal and burnt-up wood bits left over. Taking a cue from the Maya, whose slash-and-burn agricultural technique continuously replenished the soil with nutrients, I dumped the charcoal onto this problematic part of the yard.

Wednesday, wandering through a local garden store, I spotted some bags of carbon bits which, I understood from the label, were to be used to cleanse the soil in a garden. This confirmed my belief that maybe, just maybe the charcoal and burnt-up wood bits would help this patch of my garden…so I rototilled the spot, mixing up everything up. Have not yet planted anything there, but will.

Might there be any merit to this approach?

I've been dumping the dregs of my charcoal and ashes into my garden for as long as I can remember. I think I got the idea from a Victory Garden episode on PBS many years ago. I have no direct evidence that it helped but, like chicken soup, it couldn't hurt.

I also (can't verify if it actually works, but again it didn't hurt) dust plants that have had insect problems with the wood ash - the theory is it works like diatomaceous earth and give bugs a fatal case of the itchies. If you use this method of bug control, make sure you don't get any near the flowers as it will also affect the bees.

Hi,

The Victory Garden was filmed in Massachusetts where the soil is acidic, while ours is base. If you notice, they also used quite a bit of lime that is simply not necessary here.

When I used to be a Master Gardner with U of I Extension, we did not recommend people throwing ash into their gardens. It wasn't going to contribute a thing and it would raise the pH, which wasn't desirable. If you have charcoal briquette ash, then it is not recommended due to the chemicals used to bind the briquettes. I toss my ashes into the garbage.

Regards,

Cathy2 wrote:When I used to be a Master Gardner with U of I Extension, we did not recommend people throwing ash into their gardens. It wasn't going to contribute a thing and it would raise the pH, which wasn't desirable. If you have charcoal briquette ash, then it is not recommended due to the chemicals used to bind the briquettes. I toss my ashes into the garbage.

I wouldn't think any one here is using briquettes.

Question: is ash the same as charcoal? I don't think it is. I was putting basically chunks of uncombusted hardwood charcoal into the garden.

Cathy2 wrote:When I used to be a Master Gardner with U of I Extension, we did not recommend people throwing ash into their gardens. It wasn't going to contribute a thing and it would raise the pH, which wasn't desirable. If you have charcoal briquette ash, then it is not recommended due to the chemicals used to bind the briquettes. I toss my ashes into the garbage.

I wouldn't think any one here is using briquettes.

Question: does ash have the same chemical composition as charcoal? I don't think it does. I was putting basically chunks of uncombusted hardwood charcoal into the garden.

David Hammond wrote:I was putting basically chunks of uncombusted hardwood charcoal into the garden.

Beware of one-size-fits-all gardening advice, especially from sellers of garden materials. Soil conditions vary enormously in different parts of the world.

You'll likely find activated charcoal in local garden centers because it's sometimes used as a drainage medium for pots. But it's much easier to control pH in potting soil than in the garden. And I don't think that's the same stuff as goes into your barbecue.

I'd agree with Cathy that charcoal would raise the soil pH undesirably. (FWIW, I was a Master Gardener, too.) Charcoal has a pH of about 8.5. And using uncomposted wood chunks as a soil amendment risks depleting the nitrogen.

Here's an abstract of a study suggesting charcoal can have undesirable results on plants.

You might try putting the charcoal in compost heap, but you may need peat or sulfur to counter its alkalinity.

Hi,

In our area, most of our efforts are spent trying to lower the pH. Consequently ash, which will increase pH of the soil, isn't doing you any favors.

I would guess the unspent wood charcoal may be inert, though LAZ's idea of dumping it into your compost pile is an excellent one.

LAZ - I see you were a Master Gardner, too. I did it largely waiting for the Master Food Preserver program. I was one for 10 years, before moving on.

Regards,

Cathy2 wrote:LAZ - I see you were a Master Gardner, too.

Yeah, during what I think of as my earth mother phase. I also wrote a couple of gardening columns for many years.

LAZ wrote:And using uncomposted wood chunks as a soil amendment risks depleting the nitrogen.

I'll defer to Master Gardeners, but my understanding is that burnt wood results in more accessible nitrogen: "Slash burning resulted in large transformations of non-plant-available P and N in soil into mineral forms readily available to plants."

http://soil.scijournals.org/cgi/content ... t/64/1/399

Biochar in the tropics doesn't seem quite the same as stirring used charcoal into your Chicagoland garden. And the source you cited notes, "soil heating had a much larger influence on soil P and N availability than inputs of ash."

If you want to burn your yard down for experiment's sake, we'll all be interested in hearing your results.

LAZ wrote:If you want to burn your yard down for experiment's sake, we'll all be interested in hearing your results.

Some years ago at a Master Gardner conference, they had a woman who lived on a subdivision in Naperville. Her entire yard was planted with native plants. During the lecture, we learned she annually conducted a controlled burn on her property. From that moment on, I was looking for scorch marks on her house and wondered what the neighbors thought.

Regards,

In Cottonwood Falls, KS, you can pay a little over $100 to help burn a prairie:

http://www.chasecountychamber.org/

According to an NPR report I just heard, this event is now part of the local Earth Day celebration.

David Hammond wrote:Question: is ash the same as charcoal? I don't think it is. I was putting basically chunks of uncombusted hardwood charcoal into the garden.

I would assume that ash is different than charcoal (and yes, I'm talking about hardwood charcoal, not any nasty briquettes). What I use is a mix of partially burned charcoal and ash. I usually use whatever is in the bottom of my WSM after a cook. Obviously, with the amount of BBQing and grilling that I do it's not practical to dump my dregs into the garden every time. If I did that, I would have soil consisting of 98% charcoal and ash. I usually dump a batch into the soil in the spring and then again sometime around July. I feel that it not only replenishes the soil, but it also serves to aerate it a bit. I'm not sure whether or not it adds anything to the crop, but, as you know, my garden is usually quite prolific, so I don't think it's doing any harm, either.

I am not a Master Gardener, nor do I play one on the internet, so take this advice as you will, since it seems to go against the soil science present here.

Hi,

FYI - Master Gardner isn't exactly a trivial amount of effort. The initial training is around 60 hours with 60 hours volunteer payback the first year. To maintain your status it is minimum of 40 hours annually of volunteering: 10 hours additional training, 10 hours other volunteer and 20 hours answering the phones.

When I was involved, I usually did 25 hours training, 200 hours via Extension Council and Extension Foundation and 20 hours answering phones. While I don't especially like the title 'Master,' we did our best to provide research based information to the public.

Regards,

Cathy2 wrote:Hi,

FYI - Master Gardner isn't exactly a trivial amount of effort. The initial training is around 60 hours with 60 hours volunteer payback the first year. To maintain your status it is minimum of 40 hours annually of volunteering: 10 hours additional training, 10 hours other volunteer and 20 hours answering the phones.

When I was involved, I usually did 25 hours training, 200 hours via Extension Council and Extension Foundation and 20 hours answering phones. While I don't especially like the title 'Master,' we did our best to provide research based information to the public.

Regards,

I don't doubt either your commitment or knowledge. I only know what I do, wrong as it may be. I'm just providing some real world anecdotal data, but I bow to your superior scientific based knowledge.

I'm starting a U Pick Blueberry business...and the soil PH needed to be adjusted to more acidic. So if you want to grow blueberries, maybe the leftover charcoal could be used there. As for me, I bag up my left over NATURAL WOOD charcoal and use them as bonfire starters.

Wood ashes raise pH because of the potassium hydroxide in them. Blueberries require low pH (equals acid soil), so using wood ashes on blueberries pushes the pH in whe wrong direction unless you are starting with extraordinarily acid soil.

The big problem with using charcoal ashes from a grill is the likelihood of meat grease being in the ashes. Animal fat in gardens causes problems in microbial balance and can attract pests from ants to four-legged mammals.

Wood ashes are beneficial for onions provided the ashes are worked into the ground well before the onions are planted. Onions like a fairly high pH and like high potassium level in the soil.

Tropical soils are very different from soils in temperate climates. Purdue was involved is swap programs of students and faculty with a university in Minas Garais, Brazil when I was a grad student. Some of the differences reported were eye-opening. The biggest soil difference is that temperate-zone soils contain most of the nutrients with a fairly small proportion in the active biomass. In contrast tropical soils have very few nutrients while a very high percentage of the nutrients are in the living biomass. This is why slash and burn works but only for a short time.

I'm starting to line the edges of my gravel driveway with the leftover charcoal. Looks nice, keeps the weeds down.

David:
This link from National Geographic about terra preta may or may not be of interest.
http://news.nationalgeographic.com/news ... mazon.html

A lot of slash and burn agriculture is/was conducted on acidic tropical soils, (formerly called laterite, now called oxisol). In such a soil most of the nutrients are in the biomass and not in the soil. Burning does two good things: it puts the nutrients into the soil, and it raises the pH (by leaching basic ions from the ash). There's a short article here.

Back in the day, when I was just starting to garden, I sort of remembered something about using ashes in the garden that I'd read in one of the Emmaus pubs, so I blithely dumped lots and lots of ash in my KC garden, which reacted, over the next couple of years, by killing everything I planted in it. A little research, and checking the pH of a soil sample at the Extension Center, put me back on the straight path..

Geo

Cathy2 wrote:

LAZ wrote:If you want to burn your yard down for experiment's sake, we'll all be interested in hearing your results.

Some years ago at a Master Gardner conference, they had a woman who lived on a subdivision in Naperville. Her entire yard was planted with native plants. During the lecture, we learned she annually conducted a controlled burn on her property. From that moment on, I was looking for scorch marks on her house and wondered what the neighbors thought.

Regards,

C2,

I can't believe that I didn't see this when you posted it. That woman not only lives in a subdivision, but her property is on a corner with Naper Blvd. Growing up less than a mile from this place always gave us something to talk about. From what I remember both her neighbors and the city were, at least at the time, trying to get her to mow the whole thing down, but as far asI know her little garden project is still going strong..

Flip

Flip,

You affirmed what I thought was the likely situation: her neighbors couldn't possibly enjoy this activity - especially the annual burn - very much. I can easily guestimate what the over the fence chatter may be over that property.

Thanks!

Regards,

The attempt to recreate the "terra preta" super soil found in the amazon is an interesting subject.
I usually toss the fines left over in the bottom of the bag from my lump charcoal into the garden and have no idea if
it makes any difference.

Here are a couple of other sources on Biochar.

Gardening with Biochar FAQ
Financial Times Biochar article