I'm so pleased you asked :)
If you're not from a hot dry climate then you don't need to read this post.
If you are from a hot dry climate then read on and find a very water efficient garden bed design.
Do you remember those pots called water well pots? Same principle applies here:
Water will 'wick' up, via capillary action, from a water reservoir in the base, up through the soil to the plant roots.
A waterwell pot (TM and all that stuff):
Can be built in a container, in-ground or above-ground bed (ie suitable for renters as well as home owners).
Drastically reduced evaporation due to not watering on the top of the soil.
Plants have moisture where they need it (at the roots) when they need it.
Very water efficient.
Makes your garden less dependant on you and regular watering. You can go away for a weeks holiday in summer and your plants will still be alive when you come back!
Less fungal issues caused by soil splash and wet leaves (because you wont be top watering)
Can only be 300-400mm soil (the water will not wick any higher than this).
If your water reservoir leaks it can be a lot of work to fix it.
Not particularly suited to high rainfall areas.
Not suited to deep rooted plants.
For us in Perth our summers are very long, very hot and very dry. Our record is about 84 days with no rain but it's still generally over 50 days with no rain. When it does rain the evaporation rate is higher than the rainfall in all of spring, summer and autumn anyway, so the plant still doesn't really get much water when it does rain (ie rainfall only exceeds the evaporation rate for three or four months of the year).
Added to this is those dreadful Bassendean Sands that most of Perth gardeners have in their backyards. The least fertile soil in the world! Lucky us! Water (and nutrients) wash through this stuff (which is not much better than beach sand) so fast plants have to be real quick to get a drink as it flows past them back down into the water table.
There are other factors (such as blisteringly hot easterly winds in summer) but the two listed above are sufficient reasons to be looking for very water efficient methods of gardening.
I think I first heard about wicking beds at one of the free workshops held at Lockridge Community Garden. I've been attending these monthly for the last two years. Fabulous folk.
I did some web research also, there are some very useful sites and you'll see a variety of ways of making these if you go looking. The originator, Colin Austin of South Aust, is a good place to start - Waterright . Google wicking beds and you'll find heaps.
Colin came up with the idea to ameliorate erratic rainfall in trying to assist Ethiopia with food growing.
Being the sometime sceptic that I can be, I decided to follow the instructions given by Todd Smith at Lockridge Community Garden and built two wicking beds out of polystyrene foam vegie boxes last January to see how they would go during our summer.
I'll show you how they went in the next post ...
Happy gardening everyone!