An olla (pronounced oy-yah) is an unglazed, porous, clay container with a narrow neck and large belly. It is buried up to its neck in the soil and then filled with water. The water then slowly seeps out and keeps the area irrigated for approximately one week. The main benefit is that water is not lost to evaporation like many other watering techniques.
No one knows exactly where ollas originated but they have been mentioned in many civilizations from China to the Middle East to South America.
“This irrigation technology is an ancient method, thought to have originated in Northern Africa with evidence of use in China for over 4000 years and still practiced today in several countries, notably India, Iran, Brazil.” From permaculturenews.org
In the photo above we planted 2 squash plants around the olla. No additional irrigation is needed.
A large olla can water an area approximately 3 feet in circumference.
For more info see How to use Olla Irrigation.