Pine bark and vermiculite instead of gravel ?

[Cheryl Webster]

Ran across a book in the Library called: A Guide for the Hydroponic & Soilless Culture Grower", written by J. Benton Jones, Jr, and printed by Timber Press 1983,  that I fould very interesting. It coveres NFT, DWC, drip irrigation,verticle tubes, ebb and flow, etc.  One item that really caught my attention was the use of pine bark and equal parts vermiculite in the grow box (instead of the gravel or hydroton balls, that everyone uses). Quote: "The pine bark-vermiculite mix maintained its physical characteristics over the 8 year period of use, requiring only small yearly additions of fresh material to maintian the initial volume (page 73.)."

My question is: Has anyone in our community tried pine bark/vermiculte? I can find no reference to this material being used on any of the sites I've visited. Believe it would definitely be lighter than gravel and apparently the "longevity" that we all look for is good!

Thank you,

[Chip Pilkington]

Hi Cheryl,

Interesting option.

I have two areas of concern - first is pH as many things pine are acidic. Second, the lightweight property is nice from a construction and handling perspective, however, light materials are really limited in their ability to support larger plants. I have read several threads where folks have gone back to river rock from hydroton because even it's not always supportive enough. The pine bark/vermiculite would be significantly lighter than hydroton. I'm a big fan of 5/8-3/4 inch river rock - I built heavy for it, but it works really well.

That said, for the right plant selection, if pH isn't difficult to manage, it offers easy handling. You could potentially use lighter GB containers, as the weight of the media won't bulging the sides out. Then there is also the "it's fun to try new things" factor, right?  I'm thinking it would be pretty inexpensive as well.

[Vlad Jovanovic]

Wait. that's on page 163 in my copy...aha...second edition 2005...

You could maybe put a handful in a container of water and test pH every couple of days for a while. Note that he also says...

"employing composted milled
pinebark as the growing medium supplemented with limestone and..."

I'm guessing that the limestone he added was to aid with the pH..? IDK... test it out on a very small scale first. I think Chip may be on to something with the pH probably being acidic (and hence the authors use of limestone)...

Good book by the way...

  

[TCLynx]

As noted, you can run your own tests to see how it goes.

However in Aquaponics we usually water much more often because the fish need the filtration and things like pine bark and coco coir or coir husks tend to stay wetter than gravel and this could be a problem.  many people have also noticed that coir or pine bark will turn the water dark making it hard to see the fish.  And of course the pH issue.  So the question is quite complex.

Keep in mind that in Hydroponics they are working with a sterile environment so the regular sterilizing of the system and media between crops probably greatly slowed down the break down of the pine bark media.  In Aquaponics we can't sterilize since we need the bio-filter to break down the fish waste which is essentially like a composting process.  The nitrogen rich water and active bio in an aquaponics system seems able to break down and turn to "muck" many things that take far longer to break down in soil or hydro.

Now I would want to make sure I had plenty of "other" bio-filter on a system where I was testing out any sort of organic media since you might have to reduce watering cycles in the organic media mix down to a bare minimum so you might not get enough filtration from it to support your fish.

As to the pH issues of using organic media, well I suppose it depends on your source water as to if you think it's a good thing or bad.

And the comments about support for the plants are good too.

And if you go there, few people have tested this so you will be running experiments so don't blame anyone here if it doesn't work as well as you hope and if something goes wrong it may be difficult for people here to help troubleshoot since you are adding new variables that could have unpredictable effects.

[Jon Parr]

I've used course redwood sawdust in 2" netpots to clone plants before. Works great. Low pH favors rooting, and my well water is 8.2, so sawdust helps balance that. I also use it in the dirt garden to amend rabbit manure. It keeps the soil much more aerated. At the end of the season, sthe rabbit poo is gone, and the redwood sawdust looks just the same, untouched by decay. Of course redwood resists decay, perhaps pine BARK does too. 

TCLynx said:

As noted, you can run your own tests to see how it goes.

However in Aquaponics we usually water much more often because the fish need the filtration and things like pine bark and coco coir or coir husks tend to stay wetter than gravel and this could be a problem.  many people have also noticed that coir or pine bark will turn the water dark making it hard to see the fish.  And of course the pH issue.  So the question is quite complex.

Keep in mind that in Hydroponics they are working with a sterile environment so the regular sterilizing of the system and media between crops probably greatly slowed down the break down of the pine bark media.  In Aquaponics we can't sterilize since we need the bio-filter to break down the fish waste which is essentially like a composting process.  The nitrogen rich water and active bio in an aquaponics system seems able to break down and turn to "muck" many things that take far longer to break down in soil or hydro.

Now I would want to make sure I had plenty of "other" bio-filter on a system where I was testing out any sort of organic media since you might have to reduce watering cycles in the organic media mix down to a bare minimum so you might not get enough filtration from it to support your fish.

As to the pH issues of using organic media, well I suppose it depends on your source water as to if you think it's a good thing or bad.

And the comments about support for the plants are good too.

And if you go there, few people have tested this so you will be running experiments so don't blame anyone here if it doesn't work as well as you hope and if something goes wrong it may be difficult for people here to help troubleshoot since you are adding new variables that could have unpredictable effects.

[Jon Parr]

Sorry, TC, I didn't mean to include you're comment as if I were contradicting it. I just tapped the wrong reply icon. :)

[TCLynx]

No prob

[Cheryl Webster]

Interesting points!  in the past I've gardened extensively in raised containers with pure rabbit poo amended only with a mixture of various types of saw dust that maintained most of it's texture at the end of the season. obtaining "great results" with the veggies. Currently have a 40 hole NFT system and in 3 weeks plan on starting a 120sf  DWC system. So will now add 4- 6sf tubs to the NFT system and do a little experimenting with milled pine bark, also pelleted pine used for horse bedding. If something does go wrong, no great loss. better there than the bigger system. And can always expand the larger system later if I find that it does work.  

[Jon Parr]

Cheryl, check out Vlad's group Fishless Systems. He has come up with something he calls dual root zone, and it may be a way to experiment without risking your system. I'm setting up several experiments now with more traditional organic soil gardening styles mated with aquaponics. I'm a big fan of rabbit poo, having fantastic success with 80% poo/20% sawdust from my sawmll, which is mostly redwood, and fairly course like 1/4" cubes, plus shreds of bark, finer dust, and mill slash.

[TCLynx]

I'll drop in my normal 2 cents here about warm blooded animals and their manure and how I believe it should all be well composted before use to grow any veggies you might eat uncooked.

Now I'm totally not poo phobic but I also know that composting is the proper way to take care of pathogens.  Now everyone must make their own decisions so I'll stop there.

[Cheryl Webster]

Thanks Jon, checked out Vlad's group, will continue to follow!

TC, I can appreciate your concern about the pathogens; when I collect the rabbit poo from under our rabbits off of the raised collection platform and scoop it into the wheelbarrow, it gets "turned" then the next step is to add the sawdust, turning the wheelbarrow load again to mix it.  Then it gets shoveled into the 2'X3'X16" deep raised tubs, again turning it.  Where it then sets, heating to such a degree that there is no way to hold your gloved hand in it on the 2nd day. I also place a sheet of black plastic  over each tub and this is left to sit for at least 30 days or longer with the sun beating down on it., depending on how early in the season I get started prior to my planting date. At planting time, I again take a shovel and turn each tub then plant.  So it has been "well cooked" prior to use.   Thus, I feel that we are doing the same thing as traditional composting, just by passing the step of piling.  We used to have over 2000 rabbits, but have cut down to around 350, and from 50 grow tubs down to 25. So any way we can cut out a step, we do to save work and time!  LOL.

 

[TCLynx]

Cheryl,

      Very good.  Composting is composting, it doesn't require a big pile or fancy bin, just the right mix to heat up and the less it heats up the more time it should get.