Self Watering Container Reservoir Idea

10 years ago

Hello,

I have been trying to grow peppers and tomatoes in self watering containers and top-watered containers for the last two summers, and have slowly improved my growing success but have found it very difficult to keep the plants sufficiently watered if I'm away for more than a day or so.

For the SWC I use Raybo's 3:2:1 and for the top watered I use Al's 5:1:1. both in ~7 Gallon containers. The reservoir in the SWC holds about a gallon.

The issue is the plants are on a rooftop terrace where they get full sun for almost the entire day and it gets very hot in midsummer, causing the plants to burn through their reservoirs very quickly. If I'm away for the weekend I can expect to come back and find them all wilted, which can't be good for their productivity.

So I have a plan and wanted to check if anyone here had tried something similar first...

This summer I plan to construct reservoirs out of timber, with a polyethylene lining, punch holes in the pots (they're fiberglass or plastic) and out the pots in the reservoir. I plan to put a lid on top to help control evaporation, prevent algae bloom and discourage mosquitoes.

The containers will be 6 feet long by 1 foot wide by 6 inches deep (made out of 2x6 timbers) and each will have three pots in it. With a water depth of 3 inches the reservoir will be about 11 gallons, so about 3.5 gallons per plant. If I go to 4 inches water then the reservoir will hold about 15 gallons, or 5 per plant. Which should be plenty to keep the plants watered even if I'm not able to attend to them for a few days.

So... are there any issues with this plan?

Will I have problems with mold / fungus in the reservoir? Or no more than with any other SWC?

Is it OK to just put holes in the pots so water can get into them?

I plan to just have the pots filled with 3:2:1 mix, even in the section that will be submerged most of the time. Is there an issue there?

Would I need to put a ton of fertilizer in the reservoir?

Below is a rough sketch of what I plan, made looking along the reservoir so you only see one pot.

Comments (7)

emgardener
10 years ago
the bottom 3" of roots will be submerged in water, don't think they will like it.

Why not just buy a timer and put in a microsprayer:
C-Frame, 360ÃÂ° Micro Sprayers
http://www.dripirrigation.com/drip_irrigation_categories/112/drip_irrigation_families/321

My potted plants are doing much better since I switched to these.
They don't need to rely on me for regular watering. And they don't have the overwet problems swc's have.
petrushka (7b)
10 years ago
what about earth boxes? have you looked into it?
i've seen a lot of posts here using rubbermaid tubs as water reservoirs.

Here is a link that might be useful: nice SWC setup
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gyna It looks like there's no soil wicking chamber for this gadget, so, yes, you'd better add a wick that dangles down into the water reservoir from the soil. Can you make a slit or hole in the bottom of this reservoir-provider for the wick? Lots of posts address the best wicking material in this CG forum, and you have several choices. Your soil should not be dry, just pleasantly damp. But even worse, there's another issue: no provision is made for watering it too much. Your plants can die for lack of oxygen because water covers their roots. You'll need to drill a small overflow hole in your container at the top of the water chamber (just below the base that holds the soil). That way your overflow hole will allow for the draining of too much water but still leave you with the deepest possible reservoir. Put some kind of water-saucer under your container to catch any watering overflow, or else water it where it can drip. You can certainly mulch the plant once this thing works. It'll prevent water evaporation from the soil surface. What are the instructions for containers that have drainage holes? I'd think you'd have to stop them up some way.
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As I was thinking more about this, I will plan to flush the tanks monthly. Before I refill them, I can let it sit empty for a couple hours to get some more air to the bottom of the wick. Hopefully that should keep the mix happy for a few years. If you are using potting mix for the wick you do not need to worry about it's condition at all. The only purpose it serves is to wick the water upward and everything else being equal the more broken down it is the faster it will occur. Common advice when filling a container is to not tamp the mix down, but just water it in. This is to reduce compaction. This advice is reversed when it comes to filling the wicking chamber with potting mix. In this case you want to mash it down firmly so the particles make good contact with each other. Best to prewet the mix as well so it mashes down even better. This distance the water has to travel before it makes it to the growing area of the mix is considerable with your design. I would recomend testing the design this winter and see if water wicks efficiently, particularly when the reservoir is near empty. If not you can try using a different mix in the wicking chamber. Peat works exceptionally well in the wicking chamber. Basically the qualities you want in the wicking chamber are the opposite of what you want in the growing area. Your wick has to overcome gravity and if you need the water to travel upward 12" before contacting the growing media you want a water sponge. The climate here probably won't cause me to use too much water. I am about a mile from the coast and barely saw summer temps break 85. Oh, you will be fine then. Most of the folks reporting having to refill the EBs 2x/day with tomatos are dealing with hotter and drier conditions. For me it was never more than 1x/day with a 4 gallon reservoir and that was with 6'tall plants, unpruned and bearing fruit.
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Ohiofem 6a/5b Southwest Ohio
10 years ago
If you have the technical skill and money to build such a thing, I think you would be better served to build or buy much bigger self watering containers. An Earthbox holds 15 gallons of potting mix and 3 gallons of water. An Earthtainer holds 30 gallons of mix and 10 gallons of water. A full grown tomato plant uses at least 1 gallon of water a day, according to what I have read. If you buy or set up an automatic watering system, you wouldn't have to worry about watering.

I don't know how your system wicks water. It appears that you plan to set up the pots so the potting mix is in direct contact with the water, which could be a disaster.

Full disclosure: I have never grown in a SIP. I got one for Christmas and have been doing a lot of research on how they work.
ehsteve
Original Author
10 years ago
Thank you for your responses.

I suppose my goal is to construct something like an earth-trainer but with removable pots.

The terrace is about 40 feet of stairs above the ground level and it'll be rough carrying a 15 gallon container of dry soil up there and then back down come fall.

The pots themselves are about 16 inches tall, so would provide at about a foot of soil above the waterline, from where I intend to wick directly into the pot.

Looking at Earthtrainer the idea (to me) looks similar:

http://www.earthtainer.org/images/earthtainer_diagram_2__18av.jpg

But instead of the whole lower section of the pot being submerged only portions of it dip into the water.

If this is a critical detail then I could basically add in a layer of filter fabric and filler in the base of the pots so that only a section of the container soil dips into the water - would that address the issue of waterlogging somewhat?
petrushka (7b)
10 years ago
yes, only part of soil (soil-well) is critical. it is a wicking well.
if you want to use a filler - it needs to be a wicking filler to deliver water to the roots. you could use leca/hydroton or lechuza aggregate for that. the roots will grow into it over time, but you'll need to top water in the beginning. neither one is cheap.
there are self-watering insets of all kinds that have a well dipping into water - you insert them in your pot with water. you could use another bucket underneath to hold water, then insert - probably needs to be propped up high somehow above water. and then your soil pot.
you need to search for var keywords - there's a lot of posts with diff set-ups in this forum. check also hydroculture and do a google on 'lechuza pots' to see how it works.
ehsteve
Original Author
10 years ago
Thank you - I didn't realize there would be an issue with having the whole pot submerged to wick compared to just having a limited wick extend into the reservoir.

In my previous iteration of SWC's I used upturned salsa jars (about 4" tall) to support a plywood sheet with a pair of holes cut in to allow the wick down to the water and with a filter fabric to prevent soil loss into the reservoir. I'll see if I can adapt that system to make sure there is an air gap between the growing soil and the high water mark.
petrushka (7b)
10 years ago
i use self watering wicks for a lot of my indoor container grown plants. i use various ready made mixes like 'palm/citrus' or cactus or african violet mixes that contain less peat then regular bagged miracle-grow mix and then i add 40-50% more perlite for wicking. i think you need that much perlite fro it to wick properly, but stay aerated.
i use braided nylon rope for wicks. usually for 12" pot i use 2 wicks. for thirsty tomatoes you might need 4-6 wicks per bucket. the larger the bucket the harder to wick the water up.
why not use bucket in bucket system: drill holes thru the bottom of one, drop wicks thru, fill bottom bucket with water.
the bucket will sit very high up. you can snip an opening in the rim of the bottom one to allow for water refill.

Self Watering Container Reservoir Idea

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emgardener

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emgardener

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