Hot beds with wood chips?

[Tania]

Did anyone build a hot bed with fresh wood chips? If so, what should be the depth of the chip layer under the soil/compost layer to provide adequate heat for a 2 month period?

I know from my own experience, that fresh wood chips will heat up quite a bit.

They will heat up very nicely when layered with coffee grinds and sprinkled with some blood meal and kept moist. A small pile 3' tall and 4' wide will heat up very well.

But I am unsure about smaller piles (2' tall) would heat and if so, for how long.

Please share your experience.

Tatiana

[Tania]

OK, an update on the 1.5' tall pile of wood chips layered with coffee grinds and sprinkled with blood meal (I think blood meal may not even be necessary, as our wood chips are 'ramial chips' and have plenty of 'greens', as they consist of young branches)

The pile is 4'x4' at the bottom and 1.5' in height. It is watered to make sure everything is wet (these chips are notorious for staying so dry!). It is covered by plastic bags to retain moisture.

After 4 days, the pile started to heat. The thermometer inserted at 5" down shows 136F. I think it is much hotter down, but I have not dug to check.

Will leave it there to see how long it stays hot.

The coffee grinds layers are ~1", and the chips layers are about 3-5", but chips compacted quite a bit, so probably got down to 1". About 2 Tbsp of blood meal per each layer of chips/coffee.

[Zana]

Sounds promising Tania. Any idea how long this will take to breakdown or do you add soil/compost on top to plant in?

[Tania]

Zana, I have no idea - first time experimenting!

We are thinking about building a plywood box 4'x8'x2', fill it with the layers and put a piece of plywood on top. Then cold frame comes on top. The cold frame will hold seedlings in February/March.

I am hoping it will stay warn enough, so we can leave the seedlings there for the night.

So far it looks too hot to plant anything there, even if you top it up with 1' compost/soil. I think the soil will be too hot. Plus, it will not be possible to stir the pile when it start to cool down (that will be necessary to give it another 'kick' for heating up again).

[Tracydr]

Originally Posted by Tania

Zana, I have no idea - first time experimenting!

We are thinking about building a plywood box 4'x8'x2', fill it with the layers and put a piece of plywood on top. Then cold frame comes on top. The cold frame will hold seedlings in February/March.

I am hoping it will stay warn enough, so we can leave the seedlings there for the night.

So far it looks too hot to plant anything there, even if you top it up with 1' compost/soil. I think the soil will be too hot. Plus, it will not be possible to stir the pile when it start to cool down (that will be necessary to give it another 'kick' for heating up again).

A few years ago I had some new raised beds and no dirt to put in them as our house in AZ was "landscaped" with a foot of gravel, river rocks and had a hard pan caliche underneath.
I have horses and I cleaned out the paddocks, adding pick-up loads to the garden to fill it to the brim. I planted directly into this ( most of the manure was very well aged) and then planted directly in it. It warmed up for a few weeks and the seedlings grew like crazy. Luckily, it cooled off as the weather was heating up.
That was the only year in AZ that I got a decent crop of tomatoes, although that was probably weather related more than anything.

[Zana]

I am new to this whole hot bed concept, and need to do more research on it to fully understand. But I like the idea. Perhaps, it would take a year or more for it to break down enough, and thereby cool down enough to use as a base for new bed. Or perhaps it becomes a permanent location for cooking up organic matter for soil augmentation - constantly restarting the hot bed?

I would love to try something like this, if I was staying here. But as I plan to move, I don't being able to try it exactly like this in the very near future. However, I tried something slightly different, but not in a "bed". About 2-3 years ago, I purchased a number of large rubbish bins on wheels. Where I lived at the time, I put one on the deck and threw all my kitchen waste and other compostables into it. I had drilled some holes in the sides near the top for air. And would wet it down with water or snow, depending up the time of year....but mostly I used this during the winter, as I did have a regular composting bin that was hard to get to in the winter. The contents heated up enough to melt any snow that piled up around the bin within an hour or two of the end of a snowfall....even if I had 1-2 ft high drifts up against the bin. The black plastic attracted and held the heat from the sun, too, so the combo seemed to work well.

So what I might do is try the same kind of contents in the rubbish bin as you've put in your hot bed and see how that works. Here I have plenty of sources for branches and other stuff like that to add in the bottom. (Still have a huge pile of branches in the yard from last year's summer storm and the December ice storm.) At least the bin and contents would then be "portable" for when I move.

[Tania]

Zana,

If you have branches, you may want to try Hugelkultur beds.

As far as the compost heating goes, I believe it will only heat for a short period of time (a few weeks?) and then it will cool down. If you stir the pile at this time, it will reheat again, for a brief period.

So yes, you will have to start a new hot bed every spring.

Our goal is to provide seedlings with warmth for 2 months, so I am testing if the pile will stay hot for that long.

By the way, our kitchen compost pile never gets as hot as the wood chip/coffee grinds pile. The latter one is really steaming!

Where are you moving to?

[Tania]

our local tree services just called, and told me to expect another dump of wood chips today - ~14 cu.yd, so we'll have plenty to experiment with

They prune trees in our area and use our driveway as a dump for wood chips. Mutually beneficial!
Stan raids the Starbucks garbage bins on the way from work and brings 1-4 large bags of coffee grinds 3 times a week.

So we are all set to recycle the 'waste'.

[Zana]

Tania,
Have not found a place yet. Looking for a house rental that will allow gardening AND will allow a dog.
My previous rental said okay initially when I said I wanted to set up container gardening in the driveway and/or backyard. It was a condo townhouse complex, and my landlord owned 11 out of 38units. But some of the other owners complained...and there wasn't enough daylight with a raised deck in back and a 6' fence about 5 foot beyond the deck. And the backyard faced east. Soooooo....this time I'm going to get it in writing if its a townhouse I find, otherwise I'm looking for a house. So still looking...meanwhile most of my gardening this year has gone down the tubes. I had started seedlings but with the very late spring, and having to be away in both April and May for about a week each (and the person who was supposed to watch over them, didn't), most of those died. And then got hit with a late frost that killed most of the rest of the tomato and pepper seedlings. Since I was planning on moving I didn't start all that much - certainly not my usual quantity. Oh well, c'est la vie!

[JJJessee]

My grandmother used to make hot beds in the spring using moss they gathered from rocks in the mountains.

Last year in early April, I got the bug to give it a try and dug a 4x8 about 18" into the clay to insulate my hot matter.




I used semi-fresh horse manure that had hay and sawdust bedding mixed in.
My trouble began when I used an uncycled topping mix to plant into.



Fried tomato plant
A week later it had cooled to 120° at 15" deep. Being in zone 6b, we were still getting temps in the 30°s but row cover and milk jugs kept the plants alive.



They failed to thrive however and whether nitrogen burn or cold air stunting, it took them a long while, if ever, to get into growing-gear.

But I did end up with an excellent little crop of Green Striped Cushaw by early August





Also I direct seeded some Chocolate Bhut Jolokias in late April that almost caught up.



The plant remained small and no pods ever ripen before frost hit in mid-Oct.
Notice by the discoloration on the side boards the soil had settled a good 6" over the summer.

I re-vamped the bed for this year, but no hot matter, and grew a decent crop of Asian mustards followed by my best efforts to date with eggplants.



I'm sure I'll try it again some sunny, early spring day when my inner-groundhog is itching to move some dirt.

[Tania]

JJ, Thank you so much for sharing your experience!

And wow, that was a lot of digging!

I am not sure I understand what the 'uncycled topping mix' is.

It is very interesting how tomatoes did not thrive, but the squash did very well in the same bed. I am puzzled and curious.

[Whwoz]

Just reading through this made me remember some things, one similiar to JJ using fesh cow manure dug into the ground, the covered with soil and an old disused window over the top. Got the seedlings away well that year, but also the weeds.

Another was a dump of tree trimmings - around 5 cubic meters of Eucy mulch that steamed for weeks without turning, never stuck a crow bar or similiar into the heart of the pile, but it would have been 50C+ in there. This type of compost in a big pile will autocombust at 75C if opened to the air. The crow bar acts like a rough thermometer - shove it in to the center of the pile, leave for 3 minutes and see how hot it is when it is pulled out. In a really hot pile you will not be able to hold the bar as it comes out it will be that hot.

The third event that I will mention here concerns 1 cubic meter bins of radiata pine bark based potting mixed that were mixed up on a hot Ozzie summers day a few years back, they re-started composting, got up to 55C and were still over 45 two months later.

Woz

[JJJessee]

Originally Posted by Tania

JJ, Thank you so much for sharing your experience!

And wow, that was a lot of digging!

I am not sure I understand what the 'uncycled topping mix' is.

It is very interesting how tomatoes did not thrive, but the squash did very well in the same bed. I am puzzled and curious.

Yes, a lot of digging :-) A warm day in early spring causes gardener nesting behavior.

It was strange that the squash was only thing that went along reasonably well. It stalled right after germination, but that could have been the temps. Last year it was cooler than normal and seemed to rain 3 out of 4 days -tomatoes didn't stand a chance.

The uncycled topping material was some older verisons of the horse dung plus a little clay and looked good to me but something was out of balance. It was plenty black enough, but maybe just sawdust and dung, even a few years old worked by worms, are not nutrient balanced enough. I've done some reading on a particular 420 site that has really made me more aware what works in soil building and what and why it doesn't.

Originally Posted by Whwoz

.....
The third event that I will mention here concerns 1 cubic meter bins of radiata pine bark based potting mixed that were mixed up on a hot Ozzie summers day a few years back, they re-started composting, got up to 55C and were still over 45 two months later.

Woz

Wow, Woz. That blend must have been spot on to reactivate and last so long.

[Whwoz]

JJ That potting mix was made by one of our leading manufactures and they had a problem with that heating whenever they filled bins if the day temp was over 35C (95F). Even pouring chilled water through the bins failed to stop it heating. Out of curosity we had one of the bins held for a couple of months to see how long it took to cool down.

This heating basically pastuerised the mix and cause problems with the fertilizer that had been added to the mix causing plant growth defects. Boron was the main element affect if I remember correctly.

Woz



[QUOTE=JJJessee;
Wow, Woz. That blend must have been spot on to reactivate and last so long.[/QUOTE]

[Tania]

Woz, that's awesome info, thank you!

Tatiana