In last week’s Gardening for You column (July 12) were some water principles to consider for optimizing growth and development of crop plants. In today’s column is a nifty water delivery system that keeps plants hydrated on hot July days.
Traditional water delivery systems that supply water to plants include sprinklers, soaker hoses, hand watering, and drip. But there is an ancient method to keep plants hydrated that plant growers in arid parts of the globe have used for centuries: the olla.
The word “olla” (OY-yah) is from the Latin meaning “pot”. In fact, an olla is just that – a clay pot.
The olla hydration system is simple. A porous clay pot is buried in the soil up to its neck, filled with water then the pot is covered with a lid to prevent evaporation of water from the pot. Clay pot irrigation has been found in early writings and is thought to have originated over 4,000 years ago in China and Northern Africa (ollacompany.com).
The basic principle of an olla follows the law of chemical equilibrium, which states that substances move from higher concentrations to lower concentrations until an equilibrium or balance is achieved. Unglazed clay, such as terra cotta, is essential to allow water molecules to pass through the pores of the olla into the soil.
The olla equilibrium principle: water moves on a concentration gradient from a higher concentration in the pot to a lower concentration in the dry soil. The pot is buried, then filled with water. Water slowly seeps from the olla into the soil; when soil water has the same concentration as water inside the pot, an equilibrium has been reached and water movement ceases.
Soil moisture tension around the pot creates a suction, pulling water from the olla into the soil; the drier the soil, the faster the water moves on the gradient. Conversely, following a heavy rain that leaves the soil wet, an equilibrium has been met; water will not pass from the pot into the soil until the soil dries. This consistent water distribution keeps plants evenly hydrated, preventing dry/wet cycles.
The shape of an olla effects the efficiency of the water delivery system; large ovate containers are the preferred reservoir shape and narrow necks reduce evaporation at the soil surface. The neck and lid of the olla in the accompanying photograph is the only portion of the olla visible. The large pot has been buried under the soil surface.
Next week gives more information on sizes, where to purchase, and DIY ollas.
Plants need water but so do pollinators. Local bee keeper, thebreadsandthebees.com, reminds us bees get thirsty too. Bees drink water to stay hydrated and use it to cool their hives. Help bees by filling water stations in the garden to the brim. Place rocks or corks in shallow trays as perches so bees don’t drown.
Ellen Peffley taught horticulture at the college level for 28 years, 25 of those at Texas Tech, during which time she developed two onion varieties. She is now the sole proprietor of From the Garden, a market garden farmette. You can email her at [email protected]
This article originally appeared on Lubbock Avalanche-Journal: Gardening for You: Ollas: Nifty hydration system