Growing plants in sawdust

[tripsis]

So spring is essentially here and with it a frenzy of gardening. I was out in the yard today preparing a bed for sweet potatoes, yams and potatoes, sifting out all the rocks and gravel that were in it...hard work! Anyway, as a way of bulking up the soil mass, I was thinking of using hardwood sawdust and/or shavings. This then got me thinking of whether it would be possible to grow plants in sawdust alone.

A couple of friends grew some great chilli plants in straight horse manure over the last year, from seedlings I had grown the year before. They went very well. At least in terms on drainage, I assume that sawdust and horse manure are fairly similar (i.e. they would both hold a lot of water). Obviously horse manure has a lot more in the way of nutrients in it, but it would be easy to mix in some blood and bone, rock dust and other additives to give the sawdust a good nutrient profile. So could it be done, growing plants in straight sawdust? Would the oils/resins in the wood be detrimental to other plants (keeping in mind it's from hardwood)?. Would drainage in insufficient? I suppose another question could be, is it possible to grow plants in pure coir (outside of a hydroponic system)? If so, then coir and sawdust/shavings would share many of the same qualities, bar the oils/resins that may be present in the latter.

[ThunderIdeal]

decay of sawdust will severely draw N from the surroundings.

interesting question, i kind of imagine it getting too wet and having no air spaces *shrugs*

[tripsis]

Good point about the nitrogen loss. Regular fertiliser might combat that, but it's far from ideal.

I too imagine it staying saturated. Perhaps the straight horse manure worked because it wasn't even broken up, thus leaving pockets for air.

[Marcel]

I wonder if the oils/resins/tannins/etc in the sawdust would inhibit certain forms of microbial life, and cause others to be over-represented? Maybe you'd end up with some pretty inert plant medium.

Do you have a good source of untreated hardwood sawdust, or is this just a hypothetical? That stuff is hard to find, in my experience.

[dbbard]

Unless the waxy parts of the cells (lignum /cellulose ) are broken down the saw dust is difficult to wet again after it dries out.

Edited August 16, 2011 by dbbard

[tripsis]

I've found a limited source for it Marcel.

Soil with a high organic content is often the same in that it becomes hydrophobic once dry. The idea would be to keep it moist.

[Moses]

cant see why not i worked for a hydo-tomato farm that just used plastic shopping bags full of sawdust and sat the rockwool cubes on top with a dripper in them,so as long as you fed them well maybe pellet manure in the sawdust for slow release ferts

i can still remember slitting and emptying 25,000 bags at season end then filling 40,000 new in the summer sun.

[weedRampage]

you could age it rapidly by pouring dilute urine on it for about a month

or inoculate with wood fungus.

straight sawdust is too biologically active to be friendly to plant roots.

[ThunderIdeal]

that makes sense to me, partly composted first, maybe perlite to ensure a decent air filled porosity.

[tripsis]

Anyone know of an extremely rapid composting method of one to two weeks, which would render the sawdust useful in that timeframe? If I can use it, I'd be keen to use it sooner, rather than later.

Edit: Moses, was that virgin sawdust? How long were the plants in it for?

Edited August 16, 2011 by tripsis

[ThunderIdeal]

you could always try some other methods while it's composting. add N, water, keep it turned, if its getting hot then a couple of weeks is probably sufficient?

[incognito]

one of the big nurserys in kyogle (sells fruit trees, help me someone) used pine bark as their media. they said that it made the pots lighter and saved on transport costs. they just used pinebark and osmocote.

[tarenna]

Daley's

[ubza_1234]

i kinda realy like the idea of inoculating it with some type of eidable mushroom XP

[planthelper]

nice thread!

if you got fresh sawdust, than add urine for at least 2 weeks, it will make it much safer to use.

it can make a very nice medium! but is only good for maybe 2 years than it get's too soggy, and looses, it;s initial excellent waterholding and drainage properties.

but be prepared, that it will need constant feeding.

i would flush the system once in a while with tank water.

[planthelper]

if you want to use only fresh saw dust, consider as follows aswell.

every organic based medium will break down, and this will cause problems in the long run.

the best timbers for sawdust growing are rainforest timbers.

aswell when you source the saw dust there will be lot's of different particel size arround.

the table saw makes fine dust. the planer and thicknesser makes much coarser chips and i would use manly this material, because it has the right properties.

the material you could collect at a sawmill would be possible to use aswell.

what i mean is, mix it.

[tripsis]

I probably won't use it without treating it somehow first. Maybe I won't do it at all. Was just an idea, one that appears to have to many issues to make it worthwhile.

[Sallubrious]

If you do it the right way sawdust is possibly the best way to build soil.

Here's a few links that might be of interest.

Sawdust is my slave

Making your own soil

[tripsis]

Proper composting of sawdust would yield an excellent medium, which I will definitely be doing, but I was thinking more of immediate use.

I'll have a read of those links when I get some more time SallyD.

[Moses]

.

Edit: Moses, was that virgin sawdust? How long were the plants in it for?

 

yeah as far as i know it was plain sawdust, plants grew in it for about 8 months and got to about 10-12 meters tall

[tripsis]

Tomatoes get to 10m - 12m tall? Surely you mean feet...

I suppose 8 months is a pretty fast turnaround time, relative to using it in permanent beds.

[El Presidente Hillbillios]

I have grown potatoes one year with wood shavings and dynamic lifter. All i did was place seed potatoes on the ground, then cover them with about an inch of shavings in rows, heaps of dynamic lifter and about another three inches of shaving. as they grew through id cover them over with shavings. it was actually not a bad crop and no digging.

They down side was it took along time to breakdown and it blew off really easy, the vege gardenwaf full of shaving for about three years afterwards

[tripsis]

I was thinking potatoes should be a perfect crop for sawdust seeing as the 'no-dig' method of growing them in mulch already exists. Maybe a layer of sugarcane mulch on top of the sawdust would sort out the problem of it blowing everywhere.

[planthelper]

two more things, if you collect the chips from the sawmill, there might be somewhere a big heap of old material hanging around aswell. look and ask for it, this aged material can be used straight as mulch or potting mix!

aswell your sawdust will not fly away in the wind if you soaked it, with a water/urine or fert mixture.

i eucalypts i would leach with water first for 14 days or so,

than mix up like a quater strengh liguid fertilizer and drench the sawdust totaly in this mixture.

maybe adding extra iron, will make the chips go dark very fast, by i guess oxidizing.

after 14 day's, you remove the water/fert mixture and the sawdust is ready and will not fly away for a while, specialy if you keep the water up to it. but this stuff re wets like a dream.

never throw sawdust into an open flame or worse into an oven, dust explosions are a serious danger.

the application of fresh sawdust as mulch can work very well, i know because i used to produce a lot of sawdust, hehehe.

one more thing, if collecting always make sure it's not chipboard or mdf sawdust,

or any other polluted stuff....

Edited August 19, 2011 by planthelper

[Marcel]

Where are you guys getting your sawdust? I looked around a year ago and none of the suppliers could assure me that there wouldn't be treated sawdust among the stuff they could give/sell me.