I built a self-watering container this weekend. They contain a reservoir of water on the bottom, which gets wicked up by the soil, through a cup that hangs into the water. Picture the soil as a big sponge, with just a bit of itself sitting in the water; over time, the entire sponge is moist.
If this works, it'll be perfect for my tomatoes. Somehow, I can never water them right. Tomatoes are incredibly picky; they need just the right amount on a regular schedule. Get it wrong, and you have blossom end-rot or cracks.
Here's the screen (above) the separates the soil and the water. The two big holes hold the cups. The little holes are to allow oxygen into the bottom of the soil.
This is the storage bin I used to make it. The screen was cut out of the lid. One more hole off to the side allows for the pvc fill pipe to stick through.
And here's the finished product, before I added the soil. I ended up getting the shape of the screen wrong, leaving gaps between the edge and the container. To keep soil from falling into the reservoir, I draped a piece of shade cloth over the interior.
For more info, you can check here, or Earthbox.com to buy one. I say make your own. It's less than half the price.
Keep you posted for what grows!