Clay soil + wood dust = amazing potting soil??

Hi all

I've been doing a lot of woodworking lately with some beautiful salvaged redwood and thusly, mass amounts of sawdust have been generated. Ive been throwing the dust in our compost pile and in our chicken coop but today on a whim I tried mixing some with some nasty native clay soil.
To my surprise, a small amount of dust had a significant effect on the texture of the soil and made the unusable clay soil into beautiful aerated potting soil.

What do you folks think? Any detrimental effects as this wood breaks down? This seems like a pretty positive break through for our little growing operation

if this is anywhere near true, I owe you lunch.

Good news/Bad news.  Good news:  The doors of St. Peter's Cathedral in Rome are made of cedar.  Many coffins found in the Egyptian pyramids are made of cedar.  The bad news: Redwood will out last cedar!  Redwood sawdust will absorb a lot of water and hold it for a long time.  It will not break down rapidly in your soil.  It will improve your clay soil, but it also needs some help from other organic material that will break down (in our life times).

As sawdust in contact with dirt redwood will break down, unfortunately it will release all those nasties it uses to not break down into the soil (bad for plants) and the critters that are eating it will pull all the N and P out of the soil to do the work (also bad for plants). On the plus side you can turn it into your soil to make it more stable and less of a nasty mess.

bikemandan wrote:
Hi all

I've been doing a lot of woodworking lately with some beautiful salvaged redwood and thusly, mass amounts of sawdust have been generated. Ive been throwing the dust in our compost pile and in our chicken coop but today on a whim I tried mixing some with some nasty native clay soil.
To my surprise, a small amount of dust had a significant effect on the texture of the soil and made the unusable clay soil into beautiful aerated potting soil.

What do you folks think? Any detrimental effects as this wood breaks down? This seems like a pretty positive break through for our little growing operation

I don't have experience with redwood sawdust, but in my experience of adding (alder) sawdust to the clay soil in my raised-bed garden has been positive...given time. That's the key. You need to give time for the sawdust to breakdown, but woody stuff adds a large amount of long-lasting humus, which is a very positive thing. It is good if you can add some nutrients or other organic matter to aid the decomposition of the sawdust. Clay will also bind and immobilize many larger organic molecules, so you may not have to worry as much about phytotoxic chemicals and they may gradually be leached out by rain or frequent watering into the subsoil.

However, I would test this to be sure. Try sprouting and growing veggies or flowers in your potting mixture and at different times. Sometimes plants that wouldn't sprout in freshly mixed potting soil will a month or two later as the soil settles and balances out. I've done this inside with test pots of my garden's grey clay. After making it fertile, it's grown some of my biggest and healthiest beets and arugula, ever.

If nothing else, sounds like a stout cob brick to me

I haven't tried raw sawdust in making potting soil, but rotted wood works very nicely.

Here is a link to my method of making potting soil over at the SustainableCountry forum:
http://forums.sustainablecountry.com/forums/showthread.php?5924-Making-your-own-potting-soil&p=27189#post27189

Maybe use the raw sawdust mixed with soil for more mature plants?  That way if you have to add some nitrogen through some blood meal or whatever your preference happpens to be, it is less likely to burn them.  Seedlings can be very sensitive!

As others have said, I'd be inclined to stay away from redwood or cedar in general, but if it is very old wood, it may be just fine.

first thing I thought of was brick too, as brick is nothing but clay with a cellulose material added and then baked.

sure adding organics to clay is the best way to make clay something other than just hard old clay, but i can SEE it in my mind turning into lovely little bricks.

let me know how it works out as I have tons and tons and tons of clay here

Aye, just yesterday we made cob test bricks only using soaked clay (no sand) and not an hour later they had hardened into very solid, strong bricks!

I have heavy clays and have also experimented with woody matter integrated with it.
Some thoughts:

-Use non rot-resistant woods - or it will take much longer to breakdown unto usable components
-Inoculate with fungi if possible - find rotting material of the same species in the woods and mix it in.
-Consider that it will make a more fungally dominates soil than bacteria - so better for trees and woodies than veggies.  Add manure and bacterial-dominated material to change that a bit and promote breakdown.
-Humic acids would help - buy some or try to make some and add to the mix.
-Gypsum also seems good for clay.  Peet is amazing.
-Don't add sand as some do!

I wonder if anyone experimented with it? I use pine horse pellets as my guinea pig bedding, so I have saw dust soaked in urine (high nitrogen stuff), and I was wondering, if I could use it to enrich my soil. I could add more high nitrogen material to offset nitrogen use. I did experiment this way with wood chips already with great results ( a third off wood chips with potting mix in containers and urine). Plants put in that mix became greener instead of suffering. I realize, that saw dust breaks down faster, so it might need much more nitrogen rich source added.
 I think I will try with some plants in the pots.

I use the pine pellet horse bedding for my chickens. They turn it into wonderful compost, and I mix in dried grass from the yard for what doesn't get the (rather quickly expanded) pine pellets. The chickens seem to enjoy both options.
I have tossed a handful of non-expanded pine pellets into the bottom of a planting hole when I didn't have any compost I considered finished. I top that with fresh-ish chicken poop, add a layer of whatever I have for soil there, and plant.
My small fig trees and most of the herbs I've tried do well with this. The soil is very gradually getting lighter as the worms and other soil movers start to better incorporate the organic matter, and I have a few areas where the soil is obviously better for planting things. Unfortunately, the chickens like those places, too, so not as much grows as I'd like. Right now, those areas are primarily natives, feral fenugreek, goldenrod, and wild asters.

I like "spot treating" with the pine pellets because of the potential for problems with nitrogen uptake/release and anything that might be slowed down by so much processed sawdust in a limited area. By adding chicken poop and grass clippings, I think I can encourage good soil critters to show up and help out. And the chickens are great for minor earth moving and tillage.
I'm trying to move my annuals around the yard so I'm getting more good soil in particular places. I don't feel a need for adding too much in the way of chicken inoculated sawdust in any special place, but it's a big yard so I have plenty of space to spread things out.

So far, it's working. The areas that have seen the most  care are much lighter in texture until I dog down, and I hope that I'll be able to start turning the soil in those spots to get the lighter goodness deeper - and maybe I can try to grow carrots and daikon in my lifetime!