Don't use it on its own. It compacts very badly, and it also goes acid.
I've used it succesfully mixed with river sand, peasized gravel and perlite.
Woodchips work better.

Hey oakleaf, get yourself a copy of Howard M. Resh's book "Hydroponic Food Production". I think it's absolutely vital for anyone looking at commercial scale hydroponics, and I recommended for hobbyists as well.

With Sawdust Culture you have to make sure to steam or chemically sterilize the sawdust first and between each crop (if it's re-used). There is usually a problematic sodium chloride content in most wood, requiring pre-leaching.

There's a whole chapter on it in the book (chapter 9). The salt content of wood is especially important to check on because many logs are floated in seawater for a very long time on their way to the mill, meaning they absorb a lot of salt.

Oh, and you can't use Western Red Cedar - it's toxic.

Douglas Fir and Western Hemlock make the best sawdust for hydroponics.

Good grief I thought was good at this stuff. You guys are like unblievable when it comes to know the most strange sounding but vitally important. I mean I get it and know a lot of stuff but never would have seen the sodium chloride thing. Oh yeah thanx for the book recommendation. I will definately make it my next amazon purchase. I'll get back with you guys

Do your homework and you'll realize you don't NEED a growing medium for anything except to hold the silly plants until they can hold themselves, right?

Just to be fair, I use washed river sand for some of my stuff and rock wool for others. I grow everything from heirloom seed.

River sand is inert and almost free. It is reusable and if you use your noodle, won't get back to pumps (hint: elevate the pump in the sump!)

For 90% of my stuff, I start things in sand, then transplant to a different system when the plants are a few inches tall. Sand washes off 100% with just a dip or two.

God bless.

:O)

Yeah, the growing mediums aren't absolutely required, but they are a lot easier to deal with for many plants. The less support you get from the medium the more support you have to give the plant some other way.

Even if all you do is put a plant in a little 2" net cup with some hydroton and it grows into a 6 foot monster tomato plant, you've got a decent amount of crown support you can tap into. Media-less growing (aeroponics) is definitely possible and advantageous in certain applications, but it is also more temperamental (compared to media with water-retention and/or cation exchange capabilities), requires better technical planning, and generally is just less forgiving of mistakes.

I'd have to say that if no mistakes are made in comparable systems with the only variable being hydroponics versus aeroponics you'll probably see a bit better cost effectiveness in the aero, but the potential for loss and increased labor are a risk. In commercial applications it is far more common to see standard hydroponic systems in use.

Oh and oakleaf - I'd say at least half of what I know is still "book knowledge". I just have a brain like a sponge so I absorb it all very easily and can spit it back out. I haven't tried a lot of the stuff I know because, well, I don't have nearly enough room to do it and I'm not nearly rich enough to throw around that kind of money.

Getting into a greenhouse and doing it on the scale you're planning is infinitely better training than reading an entire library. I know I've learned more truly valuable knowledge with my hobby set-up in the basement than I did from the books, but neither is really useful without the other.

Before I did it with my own hands the knowledge wasn't "real", and trying to do it without the book learning would've been silly. You've got a good foundation and your practical work is going to build on that a hundredfold.

sawdust from a talbe saw is to fine. Need it from a mill, no need to do anything but have a well balanced fertilizer program dont forget the micro nutrients. Large scale growers buy sawduct by the truck load 53 foot trailer and just put it in narrow white bags. Never reused as it my bring pathogens with it.

I have have friends in Australia who use sawdust from a mill , which they use in long plastic trays made of soft plastic sheeting. They grow parsley for the restaurant trade, and the nutrients go to waste, with the exception that along the channels they have holes that go onto the ground beneath that the surplus nutrients allow a second crop of onions to grow, so nothing is wasted.They never reuse the sawdust , but get it from a prison farm mill.