Olla Irrigation (or as one site calls it “the original drip irrigation”)
We’ve been inspired by Fan Sheng-chih Shu. His writings from the first century BC describe a method of irrigation where a unglazed clay pot is buried in the soil. When filled with water, the clay pot turns into an amazing high-tech device. The micro-pores of the clay pot allows water to seep into the surrounding soil. A key characteristic is that the water seepage is regulated by the water needs of any nearby plant. When the plant’s water demands have been fulfilled and the soil is moist, the water seepage from the clay pot will stop. When the soil becomes dry, water seepage will begin again. This seepage is controlled by soil moisture tension. It’s automatic irrigation without timers or electronic sensors!
The link above give instructions to build an Olla Irrigator out of two clay pots. They also provide some notes on how to automatically fill the Ollas using a gravity feed.
The rest of their site is also quite interesting. They have a number of ideas for making self-watering planters out of buckets and other readily available materials, including methods to automate filling of the self-watering planter reservoirs.
I have seen the buried clay pot idea mentioned in a Bill Mollison video of permaculture in dry lands on Youtube (it could be this one).
Here is a pdf discussing buried clay pot irrigation in Africa.
via decodeencode