Update on My EarthTainer Construction - Mistakes Made, Lessons Learned (To-Date)

[rnewste]

Just a quick update after finishing 12 of my planned 25 EarthTainers. As an overview, the EarthBox Company's product is simply too small for my needs to grow large Beefsteak tomatoes, so my quest to build something 150% larger out of off-the-shelf components from Home Depot.

I am quite happy with Rubbermaid's 31 gallon "Roughneck" container. Much stronger and excellent dimensions for my application than Walmart types. My goal is to employ an internal staking system for two tomato plants per container. I am also incorporating the "stock" Automated Watering System (AWS) from the EarthBox Company, and modifying the fill tube length to adapt to my deeper container.

Some of the recent design changes are a result of actual empirical test data. The key "mistake" I made in the original design was to cut out the wicking orifice exactly to match the 9"x9" water basket I purchased from Home Depot. As this was the only model they carried, I was stuck with using this product. The error I made was by simply cutting the opening to exactly fit the basket, I wound up with an overly large 76 sq. inches of wicking area into the potting mix.



In actual use, I am experiencing far too high moisture levels in the growing mix. The darn Miracle Grow with Moisture Control is simply TOO efficient at wicking the water from the reservoir!!.



So what I am experimenting with today is throttling back the capillary action by reducing the orifice opening with two trial size openings (45 sq. inches, and an even more constrained 26 sq. inches). My goal is to find the right opening to yield a "moist" result on the meter throughout the container.



Regarding the staking system, in order to give the outer leg better rigidity, I have moved the AWS fill tube to the center edge of the Aeration Bench, see below:



So for those who are also in their DYI Earthbox construction process, learn from my experiences to avoid making my mistakes.

Ray

[dcarch]

thanks for the update.

We are all watching.

dcarch

[TomatoDon]

Thanks Ray. You are providing good and needed info. I agree, this is a most interesting topic, in all the related threads.

I guess I'm the rebel here, but if one has a good drip system and timer, I can't see the added benefit of a water reservoir EB. I can see it having a practical purpose without irrigation, but the whole point of both (water reservoir EB and automtatic irrigation) is to keep proper moisture to the plant. I have quite a few tomatoes and also blueberries I'm planning to grow in containers this year. I'm going to try 15 and 25 gallon nursery containers, 18 and 31 gallon heavy totes like Raybo, and drill drain holes a few inches up and let this be a mini reservoir, hoping the totes are deep enough (18" I believe they are) that the tomato and blueberry roots won't get too deep into the reservoir. If so, I'll just drill drain holes lower. The nursery containers already have bottom drainage, and people have grown plants this way for decades -- with the right irrigation.

Mainly, I think I've decided to rely on automatic irrigation for regulated soil moisture instead of constructing EB's with water reservoirs/baskets/areation chambers, etc. Will keep you posted.

Don

[dice]

I was thinking I might need two 5-1/2 inch round baskets
for a container smaller than those (18 gal I think it was).

Guess not.

[rnewste]

dice,

I have been monitoring the moisture content of the 2 EarthTainers with "test" orifices (26 sq. inches and 45 sq inches). I have concluded the 26" area is too small, as the moisture gauge is reading on the "moist to dry" end of the meter.

While the 45" area one is reading on the high side of "moist", keep in mind that this is only March, and when the tomatoes really start consuming gallon(s) per day, and the temps hit 85 degrees, the hydro "dynamic" and capillary wicking requirements will go into turbo-mode. So, I am going to retrofit the current 12 'Tainers with a 45 sq. inch orifice (approx 8.5" by 5.25") on top of the existing 9" by 9" wicking basket (which turns out to be a 40% reduction in surface area).

Your results may vary (Miracle Grow vs ProMix, local humidity and Summer temps, etc.), and as I already have a 3' tall Cherokee Chocolate in one of the original 'Tainers which I do not want to replant, I will use the original dimension design of 76 sq. inches as a "control" test in EarthTainer #01.

Ray

[dice]

I get 12.56 sq. in. surface area for the round baskets. (Might
need 2 after all, even in a smaller container; also the exposed
area under the platform is smaller on these.)

Last frost is still two months away here, so I can try one
basket at indoor temperatures without a plant in it and
see what happens, then just dump out the container mix
and add the other basket if it looks necessary.

Thanks for the info!

[rnewste]

Dice,

While surface area of the wicking basket is important, another "variable" I am just beginning to appreciate are the capillary properties of the particular brand of the potting mix itself. I read an older post on another thread where the poster stated that using Miracle Grow with Moisture Control caused the plants (in their opinion) to eventually die from too much moisture, and they went back to a cheaper generic mix.

I am going to try to find some alternatives today that do not contain the wicking coir that is in MG, and run some parallel moisture retention tests to compare different potting mix combinations.

Regarding the wicking area that you calculated, remember, the "original" Earthbox only has a combined surface wicking area of 8 sq. inches or so, so one basket in your design may be adequate.

I am sure an Engineer trained in water hydrology could provide a better calculation of the optimal wicking basket size per gallon of container volume, but right now for me it is more trial and observation, then corrective action.

Ray

[dice]

[Coir]

That stuff does hold water extremely well. I have a few foot-tall
plants that I started back around the first of the year in 8" plastic
pots that have about (did not measure exactly) 50% coir, 25%
rain-flushed old potting soil, and 25% sand. They take 3-4
weeks to drop from pegging the moisture meter after watering
them to the middle range at indoor temperatures.

Once they dry out enough to dig them up without destroying
the root system, I think I'll repot them again with a mix with
less coir and more sand.

That is one thing you could do to modify any MG w/MC that
you already have if it holds water too well: mix some sand
or perlite with it. (It would be lighter with perlite when
you want to rotate or move the containers.)

Edit:
That same mix (1/2 coir, 1/4 old potting soil, 1/4 sand) works
fine for smaller seedlings in newspaper pots, though. The
paper wicks water away from it from all sides, allowing it
to dry at a reasonable rate. Similarly, MG w/MC might be
more effective in a container that dries faster than it is
in an Earthbox with a steady water supply.