23 Jun 2012

How to build a Wicking Bed

Posted by bcsands

A wicking bed is a water wise way to grow vegetables. Essentially, it works by allowing soil and plants to draw up water from an underground water reservoir. Instead of watering, you simply top up the reservoir once a week in the height of summer and every few weeks at other times. The plants draw up exactly the amount of water that they need.


Building an In-Ground or Above Ground Wicking Bed?

A few pluses and minuses…

  • An in-ground wicking bed collects ground water when it rains, so it is less dependent on you adding water. The down side is it can get flooded.
  • Another plus for the in-ground system is that the plant roots are more protected from excessive heat and cold. The down side is you need to bend down to harvest the crop.
  • The above ground method allows better control of the amount of water being added. The other side is it needs more attention from the gardener.
  • The above ground system means easier harvesting, and less snails etc. The opposite effect is that the beds look artificial, and worms need to be manually added.


Here is a step-by-step guide on how to build your own in-ground or above-ground wicking bed:-


Step 1 – Dig the shape you want or build the framework. This can be made of treated timber, a corrugated iron water tank, a concrete water tank or many other building materials. Contour the bottom with sand and ensure the whole inside is smooth and devoid of anything sharp.


Step 2 – Line your bed with heavy-duty builders’ plastic to create a reservoir. Pour in a little water to make sure it spreads evenly across the whole floor area. If necessary re-shape the bottom before you carefully shovel in a thin layer of gravel, blue metal or small filter stones. Lay the ag-pipe in the centre of the bed. Join a PVC pipe to the ag pipe at one end and make sure it rises above full height of the wall, as this is where the water will be poured in.


Step 3 – Cover the ag-pipe with gravel and then place a layer of shade cloth over the top. Drill an overflow hole in the wall opposite to PVC pipe, at the transition point between the gravel and the soil. This will prevent plants from becoming waterlogged during heavy rain. Place 300mm of soil on top for maximum wicking ability.


Step 4 – Ensure the soil is at pH 7 before planting out your vegetable seeds or seedlings. Fill the bed to the top with good quality mulch. You can, at this stage, place a worm farm container on top of the bed, but this is optional.


Step 5 – Testing the system. Pour water into the PVC pipe until it begins to flow out of the overflow hole at the other end. Measure the water inside the pipe so that you know in future when the system needs water.


Finally it’s a matter of keeping the water up to the set level in the PVC pipe, and watching the results bloom and grow so you can harvest and enjoy home grown, fresh vegetables and fruits – and you can save more water by showing friends how to build a wicking bed too!

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