Here is a close up of a 12 inch clay pot buried in the ground and filled with water. The hole is plugged with plumbers putty. The lid is a cheep plastic plate which usually has a rock on top to keep it from blowing away. The pots will slowly leak moisture to the surrounding garden soil. This is a very efficient way to water the plants planted near the pots. These pots use much less water even then drip irrigation. Water only goes to the plants around the pot, not all over the garden, and as the plants dry out the soil, they pull just the moisture they need from the pots. You can see a just sprouted squash plant next to the pot.
The pots are about 3 feet apart and I plant around them in a circle.
Here is one with a circle of broccoli, Swiss chard and chives around it. These were transplants. I gave them supplemental water for a few weeks to get them started, then they only receive water from the buried pot after that. Last year I cut my water use for gardening in half by using, rain barrels in the spring, subirrigation, and grey water in the summer.
Another benefit of using the buried pots is that, without water running across the soil surface less weed seeds sprout. Using this method in conjunction with heavy mulching, I hardly ever have to pull any weeds.
In the garden right now: broccoli, swiss chard, onions, potatoes, peas, lettuce mix, garlic, beets, tomatoes, many kinds of peppers, egg plant, many kinds of squash and cucumbers.
A pretty picture to end with.