2011-04-14 / Features

Say “Hola” To “Ollas”

Ancient idea with new purpose
By Bridgit Martin

When we think of a clay pot we can envision a dry flower vase, a water urn, a cooking vessel or some such. But, who would have ever thought to use a clay pot for irrigation?

Well, it’s not a new idea. In fact, the clay pot (or porous pot, buried pot, buried pitcher and olla) has been used to support irrigation efforts of indigenous peoples for thousands of years.

Chinese agriculture references as far back as 2000 years ago mentioned this technique. More current evidence exists of this ancient technology in practice across the globe in places such as India, Pakistan, Iran, Zambia, Brazil and Mexico. It is possible the Spaniards may have brought the water-conserving method to the southwest region of the United States. This irrigation practice was originally designed for use in semiarid or drought regions of the world and would have been well suited for the desert southwest.

The technology is pretty basic. In its simplest form, an unglazed, fired clay pot is placed in the soil with its neck above ground. When filled with water, the pot seeps into the surrounding soil thereby feeding the area plants with a much-needed nutrient source. Plants placed near the buried pot benefit by getting all the water released from the pot and thereby experience less stress that attributes to growing stronger, healthier and providing more fruit yield. Because plants have a localized water source with no runoff or deep percolation, water conservation has been noted of upward to 75 percent! And, since the water is applied sub-surface there are fewer problems with weeds and pests searching for above ground moisture.


The system is suitable for vegetables as well s perennial orchard or plantation crops;

Water savings of 50 to 70 percent are realized, particularly for vegetable crops;

Soil moisture is always available almost at field capacity, giving the crop full security against water stress;

The system inherently checks against over-irrigation;

Saves on fertilizer as a soluble form goes direct to plants with no loss to runoff;

Clay pots can be instilled on any terrain;

As a subsurface irrigation system, the salts accumulate at the soil surface and at the boundaries of the wetted front, leaving the root zone in equilibrium with the salinity of the irrigation water used in the pitcher;

Clogging of pores from the outside due to salts from the soil is limited because the flux is always continuous and occurs outwards, i.e.. away from the wall of the pot.


Clay pots will break if not handled carefully;

Pores can clog if dry for too long. This can be assisted with a vinegar/water solution and a scrubbing of the pot to clean the surface;

Works best in sandy/loam soils;

Best used in small-scale agriculture;

Pots may not work well with woody type root systems.

Overwintering does not seem to be an issue. In a small plot in the mountains of Ghost Ranch, N. M., buried “ollas” were found after 15 years, finally unearthed and found to be in workable and good condition. It is helpful to seal the exposed neck with a silicone or acrylic paint application to lessen weather degradation. Don’t forget to cover the opening with a stone.

The lowly clay pot has found its way, through a long history, across the world to the far reaches of the globe to provide a smart and savvy water-conserving technology. Whether originated by the Chinese, or maybe even the Romans, many peoples of the world have and still benefit from this ancient watering wisdom.

Although each design may be a little bit different, they result in similar outcomes: lowered water needs; stronger and healthier plants; higher crop volumes; and usable in most any terrain available to them. These people may not have understood all the science behind this technology, they just knew it worked! This smart, self-regulating system, albeit crude in nature, has proved itself a success time and again in many regions, and it may be time for the lowly clay pot to make its debut into the agricultural scene of the United States.

Urban gardeners or small farmers in arid or drought regions should consider all the overreaching advantages of this technology and find ways to employ it talents in their next growing season.

For further information please attend the Fulton County Master Gardener presentation and workshop Saturday, May 21, from 9 a.m. to 11 a.m. at Butterfly Gardens, Cito Road. Learn more about how to apply this irrigation technique and make your own olla during the class. Take home for this year’s planting season. More information may be obtained by calling Donna at 485-4111 to and also to signup for a small fee to covert costs.

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