We just put in a new wicking bed module.
I have always been rather impressed with how wicking beds work and have designed and made a
small prototype module, based on similar construction methods to similar beds.
The whole system works very efficiently so far, and I am keen to see how well it compares to my other raised vegetable beds.
I already have seen significant savings in water use so far as we have had only added about 10 litres over the last 5 to 6 weeks in it. We have had about 40 mm rain though and these are only new seedlings.
I am trying to keep accurate records and will do an informal trial to compare
the two systems. So far I am impressed with this module.
I planted capsicums, tomatoe, parsley, lettuce, and celery as the first crops in this bed .
Cropping dimensions are 1 square meter.
below our new bed is planted out and now 5 weeks old
cross section of our bed .
Step one: level the site
Step two: level the inner frame, reservoir into its position.
Step three: Slide the main raised garden frame over this section.
Step four: Place the filling tube into its position. Note the slits to the bottom.
Step five: Add the sand, and fill flat to the top of the resevoir.
Step six: Place the geotextile fabric over the sand, this stops the sand and the soil mixing.
Step seven: Add the soil to the top of the bed.
Step eight: Time to plant out!
I'm going to put a pdf document on my website with more comprehensive instructions.
Lyn asked for an update, tips and conclusions ...
I now have 5 wicking beds in 200L and 300L black plastic bins I bought from Bunnings. There are a couple of dozen other self-watering pots on a smaller scale.
All seem to work just fine but I've only had them just over a year so long-term is hard to say at this stage.
Except for the manufactured self-watering pots, the wicking bins don't have a separate water reservoir. It seemed too complex for me to work with, so I simplified the making of a wicking bed. These comments relate to the 200L or 300L bins:
1. drill a 25mm hole about 50mm from the bottom of the bin. Line the hole with some shadecloth to stop the mix from falling through.
1a. add some sheets of styrene (from old fruit boxes) to the insides which will be exposed to the sun but don't cover up the overflow.
2. add 2 bags of el cheepo potting mix and spread over the bottom, don't worry about levelling it.
3. level the bin finally - should have mentioned that a level site is vital if the water is not to either pool or run out of the overflow too fast.
4. fill the bin up with a mix of perlite, vermiculite, soaked coir either fine or medium in a ratio of 1:1:1 then add as much general compost or composted manure with some mushroom compost or indeed anything else in the organic matter line that is available. Add some damp garden soil hopefully with micro-organisms in it and some either garden worms or compost worms. Wet the mix until water runs out of the overflow.
5. Add the plant or plants. Since all the plants I have put in have been quite small for the size of the bin, I have added other plants to keep them company. These have ranged from Midyims with the Raspberries to Watermelons with the Fig and Mulberry and some Okra and Buckwheat. Plants are solar-powered water pumps so to get the water to their roots, a bit of combined 'grunt' might be needed anyway, most plants like company.
6. Allow the top of the soil to dry some as this allows Oxygen to enter the soil, a necessary gas for the plant roots. Then water with a fine spray until water starts to trickle out of the overflow.
Now longevity is something I cannot determine at the moment. I see on the bottoms of the bins most in the sun a disturbing green patch, assuming it is not doing the plastic any good at all, I will be covering the bin with shadecloth. I also don't know about whether there will be a buildup of nutrients to the detriment of the plant. I figure if the plant is growing strongly and there is an active worm population there wouldn't be much to worry about (unless you get a kick out of worrying).
I have used a cover crop around the existing plant in 3 of the bins, I just harvest that by cutting off level with the soil using shears and let the greenery lie where it is. So far that seems to be OK but since I've found most of my gardens are shorter or organic matter than is good for them, I figure the wicking bins could do with a top up too and will be adding some mushroom compost later on.
So far the plants are growing well.
My sumary of those beds Rudi and I made
I have run that bed for a a bit over a year through 5 crop rotations. I have enjoyed produce from lettuce ,cabbage, tomato, silverbeet, celery, carotts, capsicum and parsley. best crop would be the lettuce and celery by far, as they required optimum water conditions.. This system is dead easy once set up. I believe Rudies identical system performed well (whilst he was in in europe his mom looked after it and had no problems sowing and growing food .)
The reason i put the bed in was to beat the neighbours palm tree roots robbing nutrients and moisture from the beds and fruit trees that were along the back fence. Those of you who remember the visit here saw plants and gardens struggeling in that area .
The wicking bed totally solved that problem though.
As a minor detail those palm tree roots actually ended up striking into the builders plastic liner for moisture and made the liner leak .. at exactly 1 year.
I quickly addressed this by replacing the builders plastic with a heavey duty poly beutal pond liner laid on a roadbase of cement and craker dust (like a root inpermiable concrete pad)
The extra cost for root and rat proofing was about $60 so all up an investment of extra $ on top of the initial costs was rather expensive .
For small scale tryout of wicking bed potential, I would probably build them from those black tubs Elaine mentioned above similar format lest cost and a smaller more manageable unit as a result.
Those tubs are great for begginer wicking bed patch, infact I see some one at melbourne flower show has them on wheels as well what a great idea. wicking bed on wheels,
As a note I only used organic home made compost and bought fertiliser (blood and Bone) over the year. The soil ph settled to a neat 6.5 within months . I dolomited prior to a bean and pea crop once, in the latter part of the rotational crop year. The rest was liquid organic fertilizer like seaweed , worm wee and one dreessing of Molases , this fires the good microbes up with a yummy sugar load..
When I changed the liner and inspected the soil and washed river sand aquifer I found no seriouse white effervesence layer from any build up of elements or nutrients. Infact the bed was well vormicasted from the resident worms depositing on top of the geotextile fabric just above the washed river sand. No worms at all in the saturated aquifer section and the washed river sand was as good as the day it went in. My soil remained friable and organic in the bed from bottom of the bed to the surface of the bed . Mulched every rotation with sugar cane mulch and or pea straw.
I would still make these to order but they need to be more cost effective and larger production size to be practical. If I lived in an arid area they would deffinately be the way to go. They are definately productive and water efficient .. definately 1/3 less water than traditional garden beds ... thats there point water efficiency ..I see them comming into there own when we realize that the cost of water and food production meets the cost of capital investment in those expensive style units I made . This in reality may not be too far away in the future in South East Queensland.
I had to try it, test it, and comment fairly .
10 out 10 for food production and water conservation. I can grow all my favorite veges with very minimal and optimal watering regime.
2 out of 10 for cost of unit. all up this unit costs relect a $350 M 2 PRICE TAG . I estimate a 5 year investment to recover costs with traditional food crops. Although if I was into a botique herb crop of oganic dope this would be a quickly recovered LOL ;)
8 out of 10 for maintainance and longevity
eg Dead easy once set up this garden reflects lower watering and garden maintainance than a traditional in ground garden bed . It has less weeding and watering for quicker rotations and better harvests .
hope this helps you all .
Mulch ... I pondered over mulching and figured, especially in the wet summer we had early this year, that allowing the bed to dry out a bit would be more advantageous than a couple of litres of water saved by mulching. Usually I only water my wicking bins once a week or less so the water saving will be significant. Although with the addition of a bag of Ness's mushroom compost, I've found the ordinary above-ground bottomless beds to be nice and moist, far more so than they were before the mushroom compost. But the above-ground beds still use more water than the wicking bins do.
OK, here's my go at translating (and remembering) what I learnt about capillary action and surface tension:
Capillary action works because of 'surface tension', which is a property of physical materials.
Basically, all the molecules in most materials are slightly charged, because they have positive and negative areas (think H2O - the two hydrogen atoms are slightly positively charged, and the oxygen is slightly negative - so the molecule overall is slightly polarised, a bit like a very weak bar magnet), or because the entire molecule has a charge (it has either stolen or given away an electron or several from another molecule - i.e. the molecule is an ion, think ammonium, which is commonly NH4+) . Either way, the molecules align themselves to each other in the material so the positive and negative parts of adjacent molecules are next to each other - in this way the magnetic attractions are kind of satisfied to some extent.
This means that at the surface of a material, the molecules are all kind of attracted to each other and to the rest of the material. This attractive force is termed surface tension - it is a measure of how strongly the molecules at the surface of a material are 'stuck to' or attracted to the rest of the material.
Different materials have different surface tensions. Mercury has an incredibly high surface tension - it's so keen to stick to itself that it forms balls on most surfaces that roll around and don't stick to anything.
If you put water in a glass and look at the surface from the side, it is slightly curved upwards where it touches the glass. Glass has a slight charge. The attraction of the water molecules to the glass molecules is stronger than the attraction of the water molecules to each other. The water attempts to stick to the glass as much as it can - so the meniscus rises up at the edges. The water can't climb all the way up the sides of the glass, because in addition to the surface tension, gravity is holding it down inside the glass.
Materials with high surface tension (e.g. oil) will form a meniscus that bends down - i.e. it's trying to get away from the container, because it's more interested in being connected to itself than to the container. If that makes sense.
Anyway, there's an interesting catch: if the glass (or any other 'sticky' surface) container is super skinny (like millimetres wide or less), the force of gravity is operating on a very small surface area, and there is proportionally a much greater area of magnetically attractive glass available to the water. In this case, the water can travel up the surface of the glass a LOT further. And there you have capillary action.
This is how plants get water to the top of a 100m Mountain Ash or Redwood - it travels by capillary action up the very skinny xylem (water tubes) from the roots to the leaves.
Any material that water finds 'sticky' will work. Think blotting paper, or hessian like in a coolgardie safe.
In soil, magnetically inert (i.e. no charge) sand grains are often (hopefully) coated in organic matter, which is usually very sticky, being made up of lots of polar molecules and ions. Clay is the same, although in addition it is usually charged by itself (containing lots of iron, calcium, magnesium compound ions etc). So water will stick to the grains of soil, and can fill up the spaces between them without draining away if the spaces are small enough. It can even travel upwards in the search for more magnetically attractive things to stick itself to ;)
This is why some clays can be waterlogged and horrible, and some sands (without organic matter on them) can be basically unwettable.
Hello Mark. Good job on the wicking beds. I have been researching them for a few years now and always wanted to put one in.
For speed and convenience I have put in two raised bed.
Now I will finally add a wicking third bed in.
Many thanks in advance.
As it turns out, it's a 'promotional line' whatever that means. I was very lucky to find them in stock when I rocked up to Bunnings on 2 or 3 occasions. Apparently you cannot order them from Special Orders, either, darn it. Anyway, you might be lucky so go to the (of all things!) Kitchenware and look on the bottom shelf for a thing described as a bulk bin for hydroponics. They come in 200L and 300L and are in the region of $60-70 each. I tried Masters too but no one has these bins or anything like them. Pest. If there's other hardware stores in your vicinity see what they have which might be turned to good wicking bin use. Other than that, there are 200L black drums and blue drums which could be cut in half but the result is fairly small especially for a fruit tree. Let us know here if you find any of these bins at Bunnings because I would like to buy some more!
Plastic mob based in Rocklea. Can you compare your tubs with a similar one from here (check the price brochure) and see the difference?
Edit: And there are no prices. I'm sure I came across this about a year ago and I saw prices...
200L Handy Tub (Regrind) Black
* 990 x 660 x 470mm, 8kg
Inventory Code: HTRG
Seems very similar. Will have to check mine in the daylight for exact size but it is 200L and was around $60 from the hardware. Looks as though you need to buy 5 minimum but if you're setting up wicking bins, that wouldn't be a problem. I suggest that if the walls of the bins are in a lot of sun, that insulating them would be best for the plants. I have used some old polystyrene from vege boxes to line the inside of the sunny side. If you do buy some, I could do with a couple more.
OK so my measuring is quite rough and I don't know if they have measured inside, outside or including the lip. Whichever ... mine are very similar in size.