Contemplating Wicking Beds

[Richard Mong]

Hello All,

I realize now that though I just posted a comment, it doesn't do justice to all the hard work I put into Google Sketchup drawings. So, here I go again. I've included the bit about my system, in general, as I'll do anything at this point to get feedback. I mean, I'm building it right now, and if something looks screwed up, I'd love to know.

System Overview

At last, a system that I'm satisfied with-- and just in time, too.

The aquaponic component is pretty simple, and I’ve gone on at length about how it works before, but here is a reminder. The fish in the tank are fed. Initially, I’ll use commercial, high-quality fish feed, but eventually I’ll transition this to a combination of worms and other sources produced on site. The water is recirculated. In fact, the fish tank water should be cycled about 18 times a day. The water from the fish tank, along with the fish poo, uneaten feed, and other waste products such as ammonia pass first through the the larger blue barrels. These are known as swirl filters. The heavier solids swirl down to the bottom of the barrels where they are removed, probably a few times a day. What’s left is water with the finer solids still suspended. This stuff passes through the first of the smaller barrels. After a lot of thought, I’ve decided to use a mixture of coir (coconut husk fiber) and rice husks in a 70:30 ratio. This mixture will be wrapped in mosquito netting like a giant teabag. Two things happen here: first, the suspended solids are trapped in coir fibers, and second, the immense surface area is home to the bacteria that convert the otherwise noxious stuff to plant food. The bacteria have other homes, too; in fact, every surface, including the underside of the Styrofoam rafts. It’s this suspended solids media that I’m particularly satisfied with (if it works). First of all, the rice husks are free, and if I can’t get coir for free, it won’t be expensive. But the great thing is that it’s all organic. Coir is rapidly replacing peat moss as the main ingredient in soiless potting mixtures. So, instead of using orchard netting as the filter media, which would have to be rinsed periodically, I can just replace it with more coir and rice husks. And what do I do with the gooey stuff? It goes to the wicking beds, of course. Let me just say that wicking beds are tremendously sexy. More about them later. The final barrels are just a “degassing” zone. Significant aeration removes methane and other nasty stuff from the water. They will also serve as a vehicle for tweaking the PH of the system water when necessary by adding hydrated lime, etc.

Aquaponic Component

While wicking worm and potato beds are a new component in the overall system, the aquaponic component has gone through some nice evolution. The greenhouse length is now more than 2 meters shorter yet maintains roughly the same level of production. There are 3 longer hydroponic troughs instead of the 4 shorter ones, allowing me to eliminate one set of filtering/degassing contraptions. The system details are as follows:

• Fish tank water volume: 8,000 liters
• Annual fish production: 1 to 1.25 tons
• Hydroponic trough water volume: 16,200 liters
• Annual lettuce production @ 3 weeks on rafts: 15,600 heads
• Freshwater prawn production in the hydroponic troughs: not sure

 Wicking Beds

Lateral drift is my best friend. The world is, luckily, full of lots of clever people. I’m not going to bore you with the science behind wicking beds; if you want more information, try reading this. From the same source, “The wicking bed system is a way of growing plants in which water wicks up from an underground water reservoir. The major advantage is a significant increase in production while water use has been shown to be reduced by up to 50% of conventional practice.”

Step 1: Wrong Way Wicking Bed

Here is how I’m intending to make my wicking beds for potato production. I will discuss potatoes at length in a later article. First, dig the reservoir pit. This is about 20cm deep. The reservoir should not be deeper than the capacity for water to wick, which depends on the wicking media, but coir can do about 30cm. Next, line it with leftover greenhouse plastic. Then put down the perforated wicking pipes. These are just fairly large diameter PVC pipes with lots of holes drilled into the sides. They are about 20cm long, too. Then lay the irrigation pipe. This can be perforated or just slotted along the bottom. The inspection/refill bit allows you to check the level of the water in the reservoir. A normal wicking bed would just use boards or something for sides, but I’m going to use old tires because I hope to get them free and worms cannot escape easily (I dare them to try!).

Step 2: Wrong Way Wicking Bed

The pit then gets filled in. I’ll probably use river gravel because it is roundish and facilitates a large volume of water. The whole reservoir then gets a layer of shade cloth. This is to keep the grow media in the tires separated from the reservoir. It has to be pushed into the wicking pipes to allow the coir-based media to get down to the bottom of the reservoir. I think this is fairly clever, but I welcome any suggestions. Other wicking beds that I’ve seen just have a corner or two of the reservoir devoid of gravel so the wicking material can be fully immersed in the reservoir’s water.

Step 3: Wrong Way Wicking Bed

The tires can now be placed on the wicking bed with the wicking pipes at their centers. As the potato plants grow, more tires are placed on top and grow media added. Potatoes are cool; the right ones will just keep producing potatoes at higher and higher levels, to a certain degree. When the stack reaches about 3 layers and the plant decides that things are going tits up, just kick over the lot and separate the potatoes from the worms and grow media and start again. I could use water from the aquaponic system, but I probably won’t have to. With worms continuously feeding on the fish poo and producing castings, there will probably be enough nutrients in the media to support a crop to maturity. Carrots, radishes, and other such things can be grown this way, of course.

Upside Down Tomatoes

I've just got to do this. Wrong Way tomatoes!

This is a subject that caught my attention some time ago and was put into one of those dusty compartments in my brain. I was looking for information about growing things in micro-climates similar to the Bolaven Plateau. The Olympic Peninsula in Washington is one such place. Cool with lots of rain and little sunshine. There is a lot of debate about whether tomatoes (or bell peppers, for that matter) grow better this way. But there are certainly advantages. These include better air circulation, inaccessibility to creepy crawly things, and the use of vertical “dead space.” This photo is from an article about a guy named Dick Schneider. It makes for very interesting reading. I’ve emailed the publisher of this article as I’d love to get in touch with this fellow. Notice how he uses black pails. This heats up the media a bit which is good for tomatoes. A disadvantage is that the growing media dries out quickly. It’s also heavy, if ordinary soil is used, but I think my soiless grow media will be okay. I look forward to experimenting.

[Chris Carr]

I don't think the point was to get someone else to do it for you if you can do it smarter and cause less work for everyone :)

Richard Mong said:

Hello TCLynx,

Yes, my wishful thinking often gets the better of me. The onion bag trick was something I read about that they do in Cuba, were I suspect the worms are far more disciplined. As for me, I'm 6' 4" with a bad back from an old high school track and field injury, so I don't like the prospect of doing a lot of bending over. My Lao missus, however, is shy of 4' 10" and can squat for hours on end doing the most tedious of tasks. As a kid, I used to have other kids bait my hook. I'll let you all know how it goes. . .

Getting back to the gist of my post, do you see any obvious problems with my wicking bed design?

[Richard Mong]

Yes, Chris, I was "mostly" jesting. TCLynx's points were very well made. Do you see any problems with the design? I'm thinking of a piece of perforated 4" pipe in the reservoir on center with the tires, stuffed with coir as the main wick. Do you think that is large enough? I'll be using standard automobile tires.

[TCLynx]

ya know Richard, you can probably go even lower "tech" on the wicking beds if you want.  I've done them as simple as a trench with some liner in the ground and then some coarse compostable materials like wood chips and sticks in the bottom and then I mound soil/compost on top.  All the stuff like gravel and drainage pipe and geotextile is just extra.  But if you have the stuff on hand go for it, I just want to let you know you don't "have to" go buying a bunch of extra stuff for a wicking bed.

[Chris Carr]

Well I really like your sketchup. It is a fun (and frustrating) tool to play around with. I agree with TC on the "lower tech" however. Is it that you have a bunch of tires accessible to you that you are using them? If you can get your hands on some food safe 55gallon/200liter barrels I would personally prefer those. You could use both ends for your wicking beds and the center ring for your worm bins or cut the barrel ends off and you can get 3 rings for worm bins out of them. For the wicking beds it should be straight forward to fill the bottoms with whatever material as TC said, and plumb the reservoir together. This is exactly what Chris Smith, this groups owner has. Check out this pics if you get a moment.

(http://community.theaquaponicsource.com/photo/2012-04-25-001-2012-0...)

Alternatively digging a trench and using the whole thing as a planting area is pretty straight forward and you don't have to worry about building wicks etc. But if you have tires already then of course use that.

For the potato stacks, keep in mind just stacking more dirt is likely good enough. you don't have to build the container higher :)

[Richard Mong]

Hello Chris,

Thanks for the feedback. I realize I can go even lower tech, but I've got to start somewhere. The tires should be easy to get, but I don't actually have any. The reason why I plan on using river gravel (roundish) is that the reservoir should be able to hold more water that way. I don't live at the site; it's sort of a great, big playground for me. In fact, it's a 12 hour drive from my home in Vientiane, Laos, and about 3 to 4 hours from my other home in Thailand. I'll be spending every other week there while I get the system up and running. I'm hoping that the worms and potatoes can go a full week without watering. I'll have local help to feed the fish and handle whatever else needs to be done in the aquaponic component, and I'll be there for the weekly harvest. So this is one less thing I'll have to have help with. I'm still convinced that tires are resistant to worm-escape as long as you don't fill them up to the rim until another tire is added. As for potatoes, I'll be growing semi-indeterminate varieties, from "TPS," True Potato Seeds. The trick is to keep building up to lengthen the underground stem and thereby improve potato yields. I'll have 3 potato plants in each stack of tires. I agree that mounding achieves the same result, but I'd need more area. The walls of the tires will keep the grow media in place. This, of course, is all theory with a lot of wishful thinking thrown in. . .

Chris said:

Well I really like your sketchup. It is a fun (and frustrating) tool to play around with. I agree with TC on the "lower tech" however. Is it that you have a bunch of tires accessible to you that you are using them? If you can get your hands on some food safe 55gallon/200liter barrels I would personally prefer those. You could use both ends for your wicking beds and the center ring for your worm bins or cut the barrel ends off and you can get 3 rings for worm bins out of them. For the wicking beds it should be straight forward to fill the bottoms with whatever material as TC said, and plumb the reservoir together. This is exactly what Chris Smith, this groups owner has. Check out this pics if you get a moment.

(http://community.theaquaponicsource.com/photo/2012-04-25-001-2012-0...)

Alternatively digging a trench and using the whole thing as a planting area is pretty straight forward and you don't have to worry about building wicks etc. But if you have tires already then of course use that.

For the potato stacks, keep in mind just stacking more dirt is likely good enough. you don't have to build the container higher

[TCLynx]

Just make sure to plan your potato "tip" zone so that kicking over the stacks for harvest won't be a big problem.  Being able to place a tarp where you will tip the stack over should help you collect the planting media for re-use instead of making a mess right next to the bed where the nice planting "dirt" will simply get trampled and wasted.

[Richard Mong]

Hello TC,

I'm pretty good at tipping things over and demolishing them. Not so good at building things. The grow media for the potatoes, as I contemplate it at this moment, will be the media that I use to filter fine suspended solids in my aquaponics system (coir and rice husks). To this I'll add worm castings and some worms, as necessary. When a batch of potatoes is harvested, the remaining media, I think, should go to the worm bins for complete transformation to castings. It all sounds nice but it will be really nice if it actually works. I wouldn't suggest this approach if you can't get coir (cheap here) and rice husks (free at the moment) economically. But as I've studied the UVI system until it can't be studied any more, I don't see the point of using orchard netting and washing away all those nutrients every week. Thanks again for your input.

[TCLynx]

Right, I was basically saying make sure you have a "tip zone or landing zone" where you can lay out a tarp so when you knock the potato stacks over and harvest the potatoes after you move the tires out of the way and harvest all the potatoes you can then bundle up the tarp and lift the used media into a worm bin or collect it for re-use with the next potato stack or whatever.

If you don't leave yourself ample space next to the potato wicking stacks to do this, you will probably be kicking yourself later (or perhaps more likely whoever is stuck trying to cope with it may want to kick you even more.)

[Richard Mong]

Got your point, crystal clear. I think it's one of those things you don't screw up very often, because you'll find yourself quite alone otherwise, and suffering the consequences.

[TCLynx]

Yep. Of course many people have to screw it up at least once in designing a set up. it is often tempting to cram as much stuff into a space as possible and it isn't until the plants have turned the place into a jungle that you realize there is no space to work. Now for personal consumption the work of harvest and planting isn't usually so labor intensive that it makes as much of a difference but as soon as you are trying for even super minimal commercial scale, it becomes very important to make harvest and planting operations very efficient. I think perhaps this one point could be the primary deciding factor in the scalability of a home/backyard system into commercial operation. At my old place my system was capable of producing enough to sell, however, the labor involved in planting/harvesting the produce in that system was not efficient because of the layout of the space since that system grew kinda organically into the space available on my small residential lot. I'm keeping planting and harvesting efficiency and space to move garden carts about in mind while setting up the new systems.

[Bob Terrell]

I have been growing potato's in tires and tomatoes for about twenty years.  I'm still here,  lol.  One thing I have done to cut down the summer heat on the soil is to paint the tires white.

Paul Smith said:

I would like to see HARD DATA about the health concerns about using tires as a grow container.  There has been a lot of talk on other forums, but no hard data, just conjecture.  I know of people who have been using tire gardens for years and there doesn't seem to be any difference in their health or the quality of vegetables produced.

As a missionary to Haiti, I have been encouraging the use of tire gardens for years because tires are one of the few resources available, many times free or real cheap.

Thanks for the input and keep up the interest, Paul.
 
TCLynx said:

There has been some debate over the safety of using tires in the food garden.  You might want to research the leaching possibilities so you can make your own informed decision before you set your heart on them.

I like the idea of using tires filled with rammed earth or whatever as retaining wall and such but I would rather not have them in contact with the moist food growing media.

If worms want to escape, they will (or they die trying,) if you create a pleasant environment for them, they tend to stay even if you are not trying to contain them.