SELF-watering systems are often referred to as automatic wicking beds.
These have a constant level of water and the moisture wicks up to the plant roots, like a wick on the old kerosene lamps.
Thirty-seven degree afternoons at the end of March in Geraldton can catch out a lot of home gardeners and pensioners trying to grow their own food to save money – to say nothing of 47oC in summer slightly inland of there.
How has nature coped with these conditions over the centuries?
Those who travel the sandplains inland from the WA coastline may have noticed the occasional freshwater soak or lake there, surrounded by a halo of lush vegetation, keeping quite fresh-looking in scorching summer weather.
There is one large example of a natural fresh water lake on the sand plain that suddenly appeared a few years ago, it is south of Coorow and you cross it on the Midland highway.
The native plants and bushes around these lakes and wetlands seem to be thriving in a natural wicking system with a permanent fresh water table level and nutrition leached down from the decayed leaves when it rains.
So, it may be possible to construct garden beds that try to imitate that.
This is the process we have been helping to develop:
Hold fresh water (from a rainwater tank) at a constant depth of about 30-45 centimetres using a toilet cistern refill valve (low pressure), using a swimming pool or dam liner and a raised bed structure or a trench.
Fill up to the outflow level with non-rottable material, such as stones, gravel, brick chips or even charcoal or wood chip
Top it off with some cracker dust (it has the mineral Feldspar in it and can provide a bit of slow release K to the plants) and then about 15cm of pure sand for the water to rise up through, as in nature – river sand is good, but most sands will do it.
Then top it off with about 23cm to 30cm of whatever compost you have (composted cow manure works a treat).
The retic used to get seeds and small plants going before they get their roots in the water can have nutrients added by a simple fertigation tank to imitate how nature feeds plants from rotting leaves.
The fertigation can be used to adjust the nutrition from N and P dominant for growth and K dominant for flowering and ripening.
Some vegetables, such as capsicums and aubergines have very tender flesh, so shade is essential.
Additionally, veges such as spuds and corn appreciate a deeper topsoil and depth to the water than others such as lettuce
We would like people to try out some wicking beds in the home garden, either large or small.
It is a great water saving system and means the garden can be left for a week without concern about watering.