Making potting soil from wood chips

This is both a cry for help and a documentation thread.

I have lots and lots of wood chips and am planting out another 3 acres of my silvopasture this year. For the test plot I bought some bargain plants for the perennial and shrub layers, but now I am seriously upscaling. I have hundreds of pots and lots of seeds and rooting cuttings to make this happen on the bigger scale but I want to start them in pots because I always move them around before planting them when I see where it is wetter/dryer and cooler/warmer once my swales and hills are in. Plus most perennials have really low germination rates from seed unless you are really fastidious.  

most of these chips have been in the piles for less than a year, but they are moist and I would say about half degraded. I was thinking about mixing in rock dust for silicates (unfortunately I didn't have any when I made the piles) and then adding coffee grounds (10-20%).

Do I need perlite to keep it from getting too wet and molding? I am really trying to do this with only waste-stream stuff (which includes the rock dust- I pretty much just pay for delivery). I tried mixing a batch and watching the infiltration and end humidity and it looks great, but I am thinking it may get more compacted and prone to rot as the chips continue to degrade.

Hi TJ.

Unless the chips have degraded almost completely, I'm not sure that you're going to get a happy result from using them as potting soil.  Yes, your plants will probably eek-out a meager existence and will limp along, but straight semi-decomposed wood chips isn't exactly the best growing medium.  

But I'm willing to bet that the four inches of soil directly below your wood chip pile has amazing soil.  THAT is the stuff you want to use.  That first couple of inches of soil below the wood chips will be filled with microbial life and fungal networks, as well as earthworms and other biota.  Once you've filled your pots and planted your new plants, you could put a one-inch layer of those chips on top as a mulch.

The key problem will be a lack of balanced nutrients, in particular, nitrogen.  Your plants will be competing with the soil, rather than working with the soil.  Wood chips are garden gold as long as you keep them on the soil surface.  If you put them down into the root zone of the plants by tilling them or burying them, you'll find that they tie up nitrogen for a year or more.  Eventually they release that nitrogen as they decompose, but during that time, the poor plant is starving and prone to disease or predation by insects looking for a sick plant.

You can try it, but I think that you'll find what I said above to be true.  It's a lot of effort to fill a bunch of pots, only to have substandard results.  Best of luck.

Marco, I know you are the wood chip afficionado so I'm grateful for your input. Even with 20% coffee grounds (and I would let it cook for a few months before planting) you think I would have poor root nitrogen? I have another free source of cacao shells which are really fluffy and high in nitrogen too. Seems like I am maybe too concerned with the tilth and not enough with the nitrogen.

As I am thinking about this I will probably make giant tubs of this stuff and saran wrap the top to get it warm. I have  a bunch of tubs for the shop that I haven't filled yet and can make mini greenhouses.

hau Tj, Marco brought up many of the issues, these issues are also in the bags of "potting soil" that you can buy at stores. The bagged stuff is amended with "fertilizer", usually a slow release variety to address the lack of N, P and K availability in these wood chip based "soils".

I know you have lots of fungi in your wood chip heaps, make good use of that resource when you are making your "potting soil".
The addition of some forest soil to each of your tubs will then have the ability to populate the mix with the rest of the microbiome plants need.
Or if you have some good compost tea, a watering with that would be superior.

Redhawk

Instead of inert pearlite you might want to think about vermiculite, it holds water unlike pearlite.
pearlite is heat expanded light aggregate it's but vermiculite is heat expanded mica, pearlite doesn't have the porous structure that vermiculite has.

Thanks Dr Redhawk for the input as well as Marco the king of cambium. Meant to reply to Marco about the subpile soil, I have moved the pile a couple times and the soil is unfortunately intermittently exposed. I have a pile off on the woods that is really degraded and should be good for fungal and maybe real soil underneath. Still too cold here to make compost tea, we had a really cold last week on the east coast. I will hit it with 48hr compost tea as soon as temps are amenable. This weekend it's back below freezing (nooooooooo!)

Here's my plan- I am going to make the mixes this weekend and let them start to cook in the black tubs for a couple weeks, which should be a good deal warmer than ambient.  My hope is that I can come up with a mix that uses just waste stream items that require minimal input, but I will do some with perlite (found a bag in the garage!) as well to see if that is really important. For nitrogen I think 20% coffee grounds or cocoa hulls (may have a line on peanut hulls too- just high N slow release) should be decent, but like Marco pointed out the microbes and chips are going to soak a great deal of that up. Maybe 30%, which would take me some time to collect. I have some bone meal, but again not a waste stream item. I'm really trying to get several yards of potting medium out of this eventually each year (there is a method to the madness, it has to do with the layout I'm installing and the sheer linear amount). The idea is that I can put in linear beds, seed them in place and establish perennials that will allow me to figure out what plants thrive where is the long term goal. Those that are not thriving will get a new spot. I have no idea where the microclimates are going to be right now, it depends on whether the department of Making Me Sad allows some ponds. They already nixed my pit burn char project which was possibly going to be epic. I may need to quit asking.

Gonna work on it this weekend and will try to remember to take pictures.

do you have a source of manure? any kind will do, in one of your black tubs fill it about 1/2 way with the chips then cover that with manure, mix well, next add the coffee grounds (dampen them first) again mix well, then add any char you might have laying around, one shovel full of soil and again mix well.
spray with water to moisten (try to stir it up as you are adding the water, we don't want it super wet), now let it sit and see if you can gather up a different animal manure for the next additions, if you have some sand, a shovel of that mixed in would work well during the second stage. Even DE can do good things to such a compost heap.

If you can move some of the outside wood chips into a wind row it will make creating them into compost a lot easier since a windrow doesn't need to be huge in any direction and they can be easier to turn if you need to do a turning.

Redhawk

Dr Redhawk,

Unfortunately manure is not readily available here. It runs $20 a pickup load, and you have to go shovel it into your truck! I'm working at a pretty large scale. Mostly though I am trying to not pay anything as much as possible. If I need to wait until year 3 on the mulch, that is my plan. I'm going to at least try this year and see if anything does well. Sorry, had a long blurb and the internet crapped out. Lost it all. Life in the country.

I made a lot less than I thought. I forgot I was out of rock dust, and I only had enough for one yard. 10% dust, 25% really degraded compost from the woods with feeder roots in it, 25% 2nd year mulch turned a couple times, 30% cacao hulls, and 10% coffee grounds.

Well its a proof of concept. It's getting rained on and when it gets moist (the cacao hulls are really dry) I can warm it up. We are getting tons of rain, should be a couple days.

I used decayed wood chips for starting my fig trees, but they are very fine chips, The tests i have seen done with fresh chips did not yield good results.

I have had a few wood chips :-)

These are just two of the chip piles, the one in front was 90-100 yards of material initially, inoculated with stropharia. It has been turned once, and has lots of deer carcasses in it. So the dog has turned it too, the jerk.

The one in back is 70 yards give or take, inoculated with a really bad attempt at mushroom slurry. Turned once.

Both have 80# of doliomitic lime and maybe a ton of rock dust between them for the silicates.

Mart, did you add nitrogenous compounds? I guess the question for me is tilth the issue or root zone nitrogen in your opinion?

So an update:

Three species planted out in 240 tree pots. 1/3 each my proprietary potting mix, commercial mix, and "composted cow manure" which on inspection turns out to be 20% manure and 80% small wood chips- which I found out later.


Species are honeylocust, coffee tree, and yellowhorn. To my knowledge these are all legumes, due to the potential for nitrogen deficiency discussed above.

Germination after boil/soaking and planted 2 weeks:
Honeylocust 80%
Coffee tree and yellowhorn 0

So this is going well!

Anyhow, the honeylocust had more germination failures in proprietary vs the other substrates. Then on further inspection, the germination was identical- but the slugs were voracious on the honeylocust in the proprietary mix. I am really intrigued by this, all of the seedlings have slug and snail damage, but the ones in the proprietary mix were torn up. I am wondering if I should have sterilized the medium as opposed to letting it get composty. Was it eggs in the planting medium or were the slugs attracted to something in the mix- all other factors were identical, they are in the same wood chip bed in labeled blocks, literally inches apart.

I'm assuming the other two will come up when they feel like it. In my experience yellowhorn takes a whole year to emerge here, with or without stratification. I'm too busy/lazy to nick the seeds.

hau Tj, sounds like a really good plan you are working on there.

I like 60 or 80 grit sandpaper in a belt sander for scarification, takes a couple of seconds maximum per seed.

I have found that the best time to plant any tree seed is when it falls to the ground if I want it to grow in the soil the mother tree grew in.
Peaches are best simply stuck in a divot, flesh and all, this method has given me a far better than average sprout rate, we don't use "good" fruits for this but the ones that have insect damage or mold.
Some of our peaches we plant come from the grocery store toss outs and I've collected lots of apple seeds from those boxes of toss outs.

I am hoping to get some citrus going from seeds this winter for next years plant out, they may not grow on my mountain top but it is worth a trial.


Redhawk

Dr Redhawk,

I would shoot McKenzie an email, he may be willing to send seeds if you promise not to compete, he is a cool guy. I'm getting some Yuzu and citrange from him. He is very knowledgeable about the many hybrids, and whether soil or temperature or fruiting period are your greatest vulnerability. My olives are still alive so I have some decent microclimates and I am also really interested in citrus. I think I will probably have to take cuttings every year to root just in case we get an arctic blast winter (which is every 10-20 years here)  but they grow very fast and I think it is worth the risk.  

I can't remember where I heard about the boiling water treatment for big seeds, but for the honeylocust it worked incredibly, and also for the caragana, which I have had difficulty establishing. Both really germinated >80%, and I treated hundreds of seeds in under a minute. I think for the coffee tree seeds scarification may be necessary (or they will just come up next year). I love lazy planting, or more specifically if it can't be done in a lazy fashion I probably won't do it. I got two volunteer peaches and a plum in the compost pile, but I like your way of planting so they have no transplant shock. Now I just have to work on my grafting. Terrible rate this year, I think I was a little late, and my bag of bud graft wood got moldy, so I am sunk until next year. Live and sometimes learn!

wood chips are the best thing ever, all you need is chicken poo or pellets  

search any video on back to eden garden

my take is that it would need some perlite or sand as an addition.
the particle size would be better than rock-dust.
in fact, i would use sugar-sand (large particles)
it would take a little time for microbes to start to pull nutrients, but not long.

ive been using a lot of sand lately in my mix
and am pretty happy with it

and yeah, wood-chips that are not properly composted can lead to a N deficiency
adding N can help, but better to have them composted well.

also, my experience with coffee-grounds is that they need to be turned, sifted and dried
if not, they can get gooey and anaerobic.
adding sand, or something to keep a bit of air pockets in the media helps a lot.
mix well...