While Ollas may seem best suited to a small, personal garden, they can be used on a much larger scale; watering crop fields with ollas is amazingly successful and water efficient.
Subsistence farmers use traditional methods to provide enough for their family. However, one farmer used ollas to take his subsistence farming to the next level. He lived in the Samalyuca Dunes, not far from Juarez, Chihuahua. Water was scarce, soil quality was poor, the desert climate was harsh, and an agricultural lifestyle was often a struggle. However, this farmer used ollas to irrigate his watermelon fields and had bountiful crop yields. He made enough money growing watermelon to send his three children to college. Desert restoration ecologists discovered that even in the conditions of the hot dry desert, he could grow 55,116 pounds of watermelon with only .12 cubic inches of water per hectare. This is due solely to the astounding efficiency of olla irrigation.
A large garden bed irrigated by ollas
Watering crop fields with ollas is completely possible but by no means a small investment; it takes time, dedication, and money. Whether one purchases the ollas or makes them by hand, it requires a lot of resources. However, ollas will not need to be replaced annual if they are of good quality. When properly cared for, they will hold up as a good irrigation system for many years.
To begin, ollas should be buried between two and three feet apart, preferably in sandy soil. Dig a hole that is about twice the size of the olla itself, and place a piece of glazed ceramic on the bottom as a surface for the olla to sit on. This reduces water loss through the bottom. Ollas should be completely buried below the surface except for the opening at the top and about one inch of the neck. Ollas should never be less than half full, or water will not seep out into the soil. Water will spread away from the olla for about as far as the largest radius of the olla. For example, if the olla’s maximum diameter is eight inches, moisture will reach soil for four inches away from the olla in every direction. When planting seeds, plant them within the reach of the water.
Burying an olla
There are several ways to make sure the ollas have enough water to irrigate the plants. Like the farmer in Juarez, one can manually inspect the ollas every few days to check the water levels. The farmer bought several large, plastic containers, filled them with water, loaded them onto his donkey, and refilled each olla in his field.
Manually refilling an olla
Modern technology allows those who can afford it to forgo the manual watering and install an automatic refilling system. Water can be stored in large cisterns (harvested rainwater is a great resource to fill ollas) and hooked up to irrigation pipes. The pipes feed into the mouth of each olla and refill as needed. After determining the rate at which the ollas drain, the watering system can be regulated by an automatic timer that refills the ollas after a fixed amount of time. For a more delicate and precise system, one can use a float fill valve system. The float remains level with the amount of water in the olla. As the water drains, the float falls with it. Once the float falls past a certain level, the refill system is triggered to release a certain amount of water back into all the ollas. However, only one of the ollas needs to be outfitted with this float fill valve system since all the ollas should drain at the same rate.
An example of an automatic olla refilling system
Olla irrigation for an entire field or farm is not a quick fix, but the benefits quickly make up for the time, work, and money it takes to install. Olla irrigation is by far the most efficient method; 95% of the water put into the olla goes to growing the plants. No other irrigation method can boast this efficiency.
Growing Food in a Hotter, Drier Climate by Gary Paul Nabhan