Wicking Beds

Wicking beds  are the brainchild of Queenslander Colin Austin.

 Austin claims that “the wicking worm bed is a highly productive growing system which not only produces food from limited water, but also recycles waste organic material to provide plant nutrient and capture carbon.”

At its most basic, a wicking bed is a waterproof box with a drainage hole drilled a pre-determined distance from the base.   A pipe is inserted into the box which is then filled with growing mix.   The pipe is used to add water to the box which drains from the hole in the side when it reaches the correct level.

Wicking Beds - perfect micropnics partners

Wicking Beds - perfect microponics partners

In practice, the water in the bottom of the box is wicked upward so that the rest of the growing mix in the box is kept moist.  This extends the interval between watering.  The addition of hollow structures (like sections of PVC pipe), create reservoirs for the water and extend the irrigation intervals even further.

Wicking beds can be constructed virtually anywhere that allows for the creation of this water reservoir…..in ground, above ground or in a wide variety of containers.

Some variations on the theme feature a worm feeding station (a section of 100mm PVC pipe will plenty of small holes will do) which is inserted into the bed.  Chopped food scraps (or animal manure) are placed into the feeding station and are converted to plant nutrients by the worms.

They’ve captured my attention for the following reasons:

  • They save water.
  • They provide the plants with continuous access to water and nutrients.
  • They can be integrated with other growing systems including square foot gardening.
  • They are very easy to water – plants get water from bottom – less fungal disease.
  • They are simple and inexpensive to build…..and easy to operate.
  • They will go for days (or weeks) without having to add water.  How long they can go depends largely on how much water can be stored in the lower section of the bed.

 …..and they would partner beautifully with an aquaponics system.

 Core Principles

  • Wicking refers to the movement of water (by capillary action) upwards through suitable soils (or other growing mixes) – like the movement of molten candle wax along the wick.
  • Wicking beds rely on the creation of a water reservoir of 75mm – 150mm deep.  A layer of soil (or growing mix) is then added – to a depth of 300mm.  The wicking action is limited to about 300mm.
  • At the bottom of the bed, the soil is very wet and at the surface only slightly damp.
  • Mulch is added to the top of the bed to minimise water loss through evaporation.
  • Plants should be fed throughout their growing cycle (rather than in one initial hit).
  • The soil or growing mix needs to be maintained at the correct level for optimum growing conditions.  If it is allowed to compact too much, the plant roots become waterlogged.

Polystyrene broccoli or fish boxes are ideal for conversion to wicking boxes – they are cheap, well-insulated and can be set up at a comfortable working height.   Fibreglass or plastic grow beds would also make excellent wicking beds.

For those who don’t mind working on their knees, a wicking bed can be constructed in ground using little more than a sheet of builder’s plastic.

One recommended growing mix comprises equal parts of clay, sand and worm castings.  There’s clearly some scope for experimentation here.  There’s a need for something fibrous in the mix (to assist the wicking action) so compost would be a desirable inclusion and even coco peat might be useful.

Watering your wicking beds from an aquaponics system would provide some nutrients and liquid fertilisers like Charlie Carp or Seasol would serve as a top up. 

Overfeeding is a risk in a closed system like wicking beds so you would be advised to feed little and often.  Periodic flushing of the reservoir with rainwater would help to avoid problems with the build up of minerals.

The inclusion of a worm feeding station is also a good idea.  Why not turn those kitchen scraps into nutrients for your plants?

Wicking beds demonstrate many of the features of the best growing systems and, as such, they are welcome partners in any microponics system.

 

-o0o-

Comments

  1. polypus says

    have you seen the setup they have over at
    growing power in milwaukee. it looks like they
    are using capillary action to suck up water
    into pots by using a coconut husk and worm
    casting based compost.

    i’m not 100% sure about that, but i hope
    to visit them in october to find out.

    do you know of anybody doing perennial
    plants with aquaponics btw?

    • says

      Polypus……I’ve checked out their web site and I like their approach. Growing food (in general) and aquaponics (in particular) is still too expensive and sites like that of Growing Power show us how it can be done more cost effectively.

      I know a few people who are growing small fruit trees and herbs like thyme and sage in aquaponics systems but that’s about it as far as perennial plants go.

  2. Bob says

    Been thinking about wicking beds as part of a system. I can see how potatoes, carrots, turnips, parsnips, horseradish, and lots of other edibles would be best grown in a wicking bed than in the trays or grow towers of an aquaponics system. I have seen a wicking bed design that has a soil pot that extends down into the reservoir. This soil pot draws the water up to water the rest of the soil in the grow bed. If we were to line this soil pot with weed cloth or some other material to prevents the soil from leeching into the water, could we suspend the grow beds over a reservoir of aquaponics water? If we did, would enough nutrient be wicked into the grow bed to sustain plant growth?

    • says

      Bob……..There are many variations on the wicking bed theme. If you abandon the perceived need to recirculate the water in the growing system back through the fish system (not essential for aquaponics anyway) anything’s possible. Give it try.

  3. Graci Northboug says

    I made a wicking bed for a friend, after a couple of weeks I put my hand into the bottom of the soil and could feel water (which was stinking) so the overflow doesn’t work. I have seen many designs of wicking beds and some have the overflow above the wicking fabric, some have it below, some say “at shade cloth level”??? The question I have is: In all designs I see, regardless of where the overflow was positioned, the water would ‘overflow’ before being moved up into the root area wouldn’t it???

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