Earth-Box Aeration Screen - - I Don't get its Real Purpose

[rnewste]

I have gotten "religion" about Earth-Box advantages and now have 12 under construction. After finishing the first one following Josho's .pdf instructions (I am using 2 Rubbermaid 31 gal totes with one cut-off, and flipped inside the other) I am REALLY in a puzzle as to the true function of what he calls an "aeration screen", bullet marked with hundreds of holes.

Specifically, he states that these large number of drilled holes are necessary "to deliver Oxygen to the roots". Wait-a-minute - - if delivering mass quantities of Oxygen to the roots for a tomato plant to grow is necessary, please tell me how in-ground tomato plants (without this aeration system) successfully grow?

My own theory is that the original Earth-box inventor (who lives in rainy Florida) put holes in this surface to drain off excess rainwater back in to the water reservoir - - NOT to somehow deliver Oxygen to the root system.

So before I call Myth-Busters to have them sort out the science of how an Earth-Box works, can someone please enlighten me if my theory is correct (holes for rainwater drain-off - - not to deliver Oxygen).

This issue is very important in my design as I want to use tomato cages resting on this inverted surface, but drilling it with a massive number of holes will not be practical (the legs can slip into the drilled holes - see photo #1) which will defeat rigging guy-wired tomato cages (like a sailboat's mast rigging). Pictures and results of my self-contained staking system to follow in a week. For now, I need to know if my revised drilling pattern in photo #2 will work before I complete the next 10 Earth-Boxes.

Thanks for your recommendations and comments,

Ray

[amideutch]

Don I'm with you. I don't think its as much aeriation as it is for drainage and a place where the roots can go to get into the reservoir. Normally aeriation won't occur unless you water the earthbox from the top anyway. Same principle as flood and drain technique for hydroponics. When you flood the growing chamber it pushes out the CO2 that accumilated in the aggregate out to the plant and when it drains it draws fresh air into the aggregate to the roots.
I've got 3 German planters that are very similar to earth boxes. They have a chamber in the bottom with a plastic grate to cover it and a fill tube plus the supports for the plastic grate are molded into the bottom of the box and are hollow with a hole at the top for drainage in each one. Of the three boxes the roots of the plants made it into the reservoir in only one box. I didn't use the fill tubes at all last year and watered only from the top. Again as the water perculates down through the aggergate it draws air along with it. Just like mother nature. Ami

BTW, nice job on your EB's!

[rnewste]

Ted,

Thanks very much for your information. I just want to better understand the "science" and water hydraulics of the Earthbox eco-system. I will be using Miracle Grow Potting Mix with their wicking Moisture Control (coconut pith, as I understand it), so I am planning on using the fill tube and rely on the M.G. to distribute the water evenly to each of the 2 tomato plants.

I am now trying to "engineer" a self contained guy wire system to rig 2 five foot tomato cages to sit inside the EB, then tether the tops of the cages to the sides of the EB (like stays for a sailboat mast, so that's why I want as few holes as necessary in the aeration shelf). I also want to be able to rotate each EB 180 degrees on its axis each month during the growing season to more evenly expose the entire tomato plant to my Southern facing exposure, so a fixed PVC trellis as some use, is not practical for my needs. This is fun stuff to figure out

Ray in Campbell, CA.

[amideutch]

Ray, I built cages out of galvanized reinforcing mesh which was about 12-14 gauge wire with 2" squares which I later cut out to make 4" Squares. I bent it to fit my round containers as well as my square containers and secured the two ends at 4" intervals with tie wraps. I made it so it either fit on top or snugly into the container and down about 2-3". Then at the top of the container every 90 degrees I drilled 2 holes above and below the cage and secured with Tie Wraps. Worked like a champ and you can turn the container no problem. And if your plants get taller than the cage just tie wrap some bamboo poles to the inside of the cage to extend. And you don't need to tether them either. Ted

[robin303]

I have been using galvanized 6x6" hogwire for years. Rather expensive. A 5'x20' is about $47 here. I bought several and just cost $40 for delivery. I used a 71/4" saw with a $3.00 abrasive blade to cut. Good stuff and worth it.

[rnewste]

Thanks for the suggestions Ted and Robin. I am planning on using two of the 60 inch tall 18" diameter round cages from Walmart ($5.00 each). With the two cages placed inside the 31 gal Rubbermaid, the 4 hoops on the cage just "kiss" on hoops #3, and overlap an inch on hoops #4 at the top. My plan is to securely tie hoop set #3 together, and bend down hoopsets #4 about an inch where they meet, to run parallel for about 4 inches. I will also secure these hoops together with wire ties. These will sit 10" down into the Earthbox (on the aeration shelf), and will give me 50" of above ground caging. I can also take additional 60" cages, cut off the bottom smaller section, and invert the upper 2 hoop sections to attach to the original cage, thus boosting the total cage height to approx 80".

I want to "tension" the legs of the two cage setup to the aeration shelf with guy wires from the joint of hoopsets #3 to the "port" and "starboard" sides of the Rubbermaid container with small turnbuckles that will give me adjustments to balance the cage system to keep it vertical on balance. I am not that concerned with any "forward " or "aft" tilting tendencies as with the two cages securely coupled at hoopsets #3 and #4, there should be good stablity on this axis.

Sounds fine in theory, but I now need to put this into practice over the next week and test with a strain gauge in all four directions. More to follow with pictures.....

Ray

[dice]

What if the earthbox is sitting on a surface that is not
quite level? You don't want water puddling up on that
raised floor when it rains. (That would be my guess why
you need all of those holes in that "aeration screen".)

If the legs for the cages are intended to go down that
far, I would just plan on having them sit right on the
bottom of the earthbox and specifically drill holes for
them (in addition to all of the drain holes).

[rnewste]

Dice,

Thanks for the observations. Regarding puddling, with the 10 drain holes I have drilled, plus the "reverse" wicking action of the Miracle Grow Mix with the copra moisture distribution, the rainwater should flow into the water reservoir, and the excess spilled out through the overflow drain hole to the ground. (At least, that's my theory).

As far as drilling holes in the aeration shelf to let the 4 legs of the tomato cage then sit on the bottom of the Earthbox, I have 2 concerns. First, over time I am concerned that the weight of the tomato plant with its load of tomatoes would eventually cause the legs to penetrate the bottom of the Rubbermaid container, causing water to drain out of the reservoir. Second, this would reduce the above-surface height of the tomato bearing cage by the depth of the water reservoir (6" in my design). Doesn't sound like much, but 6" more load-bearing height does matter!

However, you have given me an excellent idea - - to actually drill 4 holes in the aeration screen to fit each leg into, but add small diameter shaft collars to each of the 4 legs that have a set screw, and lock the collar one inch up from the bottom the leg. This will distribute the weight of the tomatoes onto the aeration "bench", and reduce the above-surface cage height by only one inch. Kind of solves two problems at once.

Now, off to the Hardware store to find the locking shaft collars (or maybe I should dig out my old Erector Set which used these collars to attach the motor to the Windmill....but I digress.)

Ray

[dice]

I thought about this more. I think the aeration screen was
just to get good drainage when it rains, to reduce the time
that the container mix sits waterlogged. (You could get rid
of puddles just by drilling a hole in each corner and maybe
one at the middle of each side.) It does let roots reach down
into the water reservoir more freely, but if there is actually
water there, the wicking action of the container mix should
provide plenty of moisture across the bottom.

I was wondering about sleeves for the legs of the cages.
Guess you have that covered.

(OT: Real masts in the days of tall ships were actually
modular. Crews could put them up and take them down
in sections. So if they expected a lot of bad weather for
some weeks to come, sailing around the Horn in winter,
for example, they could completely remove topmasts and
lash them to the deck until they were back in latitudes
where those top sections were actually useful.)

[Earl]

Aeration is important, else why has the lowly worm's contribution to plant health been touted for umpteen years? :-) I'm sure the EB guys tried it both ways and found aeration worked best. They wouldn't spend money drilling holes if it didn't mean something to their end produce sales.

[rnewste]

Earl,

Thanks for taking the time to ponder this. I guess what is puzzling me is if I place the same tomato plant in the ground, there is no "aeration screen" underneath the garden - - the oxygen getting to the roots travels from the surface, down through loose soil, wormholes, etc. to the root system.

I don't understand the need to "Rambo" the home-made Earthbox aeration screen with a machine gun. In an Earthbox, wouldn't oxygen get to the root system through the surface in the same manner as to an in-ground plant? And in fact, the potting mix used in an Earthbox is more porous than in the typical garden soil, isn't it?

So my thesis it that the holes in the "aeration screen" are more useful to drain the excess rainwater that would otherwise saturate the potting mix and harm the plant. Also, from what I know about plastic injection molding, it is less expensive to make the aeration screen with more "holes" (remember, this plastic is not "drilled out" - - instead the metal mold has fewer cavities for the liquid plastic to fill in) - right? The resulting piece uses far less plastic to form, and is therefore much cheaper to make. And the piece is much lighter in weight than a solid piece would be with only a few holes molded in.

For my own designed "Earth-Tainer" I decided to drill only a few drain holes, and this results in a stronger base on which to mount the self-supporting dual tomato cage system.

So, I may be proven totally wrong in my assumption of the true functioning of the "aeration screen" later this Summer when I see how my Earl's Faux do, but I am trying to employ rational engineering logic to this project, and in my view, only a sufficient number and placement of drain holes are necessary.

Thoughts??

Ray

[dice]

I take it there is no seal between the cage/soil support
platform and the sides of the container? So it looks like
water can drain down around the outside edges, too. You
might fill that space with sand or perlite or something
like that, and put a 1/2-inch layer of something chunky
right on top of the drainholes, to be sure that they do
not clog. Chunks of limestone or drywall might be good
choices (calcium supply). I've seen chipped up oyster shell
at animal feed stores big enough to not go through those
holes, too. Rocks, gravel, shells from a beach, lava rock
(tends to be high in iron and other minerals and low pH),
marbles, broken up ceramic tile, anything like that will do
for the drainage aspect.

[feralcatfriend]

Dice, The photo with the cages looks like he's using a box-in-box design--so there's no gap. That is, there's a smaller container that stacks inside the larger one (like a Rubbermaid 25-gallon container inside a 31-gallon one). The smaller one has aeration holes, a large hole for the basket (which sits in the pool of water from the larger container and wicks water up into the soil in the smaller container) and a hole for a fill tube that extends from above the soil in the smaller container down into the larger container so it's easy to run water down into the larger container, which serves as a water reservoir. Do I have it right? I'm curious, though, how the collar fitting on the cage leg works for the two legs that look like they are going into the same hole. Could you post a close-up photo of the collar fittings? And what did you use for the basket? Also, do you have a plan yet for staking the container so it doesn't fall over when the tomatoes are large and heavy? A staking system would help those cages, too, which will collapse under the weight of big tomatoes unless they have additional support from staking. Last year my Aunt Ginny's Purple took down her cage AND bamboo stakes. I'm asking because I grow in containers and this year I want to switch to self-watering containers. This looks like a really promising design.

P.S. I agree that the aeration holes don't seem to be there to bring air in as much as they do to keep the plant from drowning due to water filling up the upper container and driving all the air out. Likewise, the overflow hole in the bottom container keeps its water level from getting so high that it drowns the plants.

Cynthia

[rnewste]

Dice,

Good points. When I made Unit 01, I had blasted it full of holes as "josho" had instructed. I am now drilling a total of only 14 holes with a quarter-inch drill. The goal being to keep as much of the potting mix on the "bench", and not have it drop into the water reservoir. To your point of leakage around the sides, I am planning on using the "packing peanuts" kind of material to place all around the gaps so that rainwater will still be able to penetrate, but it will keep the potting mix from seeping into the reservoir.

Cynthia,

I am actually using 2 identical 31 gallon Rubbermaid containers. To "squeeze" the inverted 6" one into the base unit, I made the fit easier by making one cut down the side of the 6" bench on an acute angle to create a "slip-joint", so the inverted bench now slides easily down to rest on the base (see photos #1 and #2).

The next photo shows the collars attached to the outer 4 legs. On the adjoining leg pairs, I wanted to have as much structural rigidity as possible (and also save cost where possible, so I co-joined the leg pairs together, which met both objectives (photo #4).

Photo #5 shows the underside clamping of the two legs together, and this keeps the tomato cages from pulling up from the inverted bench when handling, etc. I did not clamp the 4 outer legs underneath as the weight of the tomatoes will be exerting a downward force, and with the cages clamped to each other at 4 places, I considered it overkill to clamp all the underside legs (photos #6 and #7).

Photos #8-#10 show the cage system, with the guy-wire support stays "port and starboard" to provide lateral support. Also, the clamp securing the guy-wire to the cages can be adjusted to offset any lean that might develop when tomatoes might weigh to one side or the other. Also remember, with approx 7 gallons of water in the reservoir (@ 8.33 lbs/gallon), there will be over 50 pounds of mass in the bottom. If this is still insufficient, one could put a sturdy Yardstick laterally under the container and add additional guy-wires from the ends of the Yardstick, up to the existing clamp, much like multiple stays on a sailboat.

My goal with this "portable" caging system is to be able to rotate the 'Tainer 180 degrees on its axis every month or so, to provide even exposure to the Sun to encourage more balanced plant production.

Ray

[dice]

If you have problems with them tipping once the plants
are their mature size, you can attach them to a plywood
base a foot or so bigger around than the container. (Use
the eyelets for the guy wires to hold the container down
on the wide base.) Then the whole container has to be lifted
up into the air before it will tip. If you put a wide base on
wheels, drill holes in it (so it is more difficult for wind to exert
any lift under it).

Hopefully the weight of water and container mix is enough,
but I have seen pictures of people's containers tipped over
with a full-sized indeterminate in them (although I don't
remember seeing pictures of specifically Earthboxes tipped
over).