Posted by: Deryn Davidson, Horticulture Agent, Boulder County
In Colorado, water has been in the news a lot recently (and the CO-Horts blog). Most notably, we have the new bill that was passed and is soon to be signed into law, which will legalize rain water harvesting on residential properties (for more information see the previous blog post). So now we all have to figure out how we are going to use this captured rain water. Well, one option I’d like to introduce is the OLLA!! Maybe some of you are familiar with this ancient, low-tech, low-cost, high-efficiency irrigation method, but it was new to me.
I first learned about this ancient irrigation technique in the book “Gardening with Less Water” by David A. Bainbridge. Bainbridge writes that he discovered the olla when reading excerpts from, what he called, “a 2,000 year old Chinese agriculture extension book”. He is referring to the “Book of Fan Shengzhi” which is a collective of agricultural masterpieces written at the end of the Han Dynasty (206BC-8AD) by an important agronomist and scientist of the time, Fan Shengzhi. It was written at the request of the Emperor with the intention of helping farmers who had limited resources learn the best techniques for farming in the Yellow River drainage area. The olla, by its Spanish name, has been used by many, many cultures for cooking, storage, cooling and irrigation.
Ollas can be purchased or homemade. To make your own (caveat: I’ve never done this but, plan on trying it) you take 2 terra cotta pots of the same size, seal the bottom of one so that water won’t flow out when it's filled with water, invert the other pot and glue the rims of the two pots together (you can use silicon or any other water proof adhesive). DONE! Now you dig your hole and bury your olla leaving about an inch above ground. Fill with water and find a nice stone to cover the hole for even less evaporation.
Everyone’s soil is little different and different plants will require varying amounts of water so there’s no one size fits all, but you can experiment with how close to place your olla to plants and how often you need to refill it.