Drip irrigation makes the most of little water

May 7, 2010

ONTARIO, Ore. – Oregon State University researchers, farmers and gardeners are turning to drip irrigation to deliver water, with little waste, to where it is needed.

Lessons learned from OSU Extension and Agricultural Experiment Station research in the driest part of the state can be applied to home gardens all over Oregon this coming summer, according to Lynn Jensen, Malheur County Extension crop scientist.

Working with commercial onion growers in Malheur County, Jensen has seen drip irrigation increase crop yields while cutting water use by half.

"Drip irrigation delivers moisture directly to the plants' root zone at a uniform rate throughout the growing season, allowing the best possible growth," Jensen explained.

In contrast, hand watering often delivers water faster than soils can absorb it, and sprinklers scatter water where it is not needed. Both methods result in wasteful runoff. Also, water delivered to roots and not leaves can help limit plant diseases.

A drip irrigation system consists of lengths of flat plastic hose with specially designed perforations (emitters) placed at the base of plants to allow water to gradually seep into the soil. Most are economically priced, easy to install and can be operated from standard outdoor faucets.

When designing a drip system, consider how water moves through your soil. In sandy soil, water drains straight down relatively quickly. In clay soils, water spreads more broadly and slowly. You may need more emitters for sandy soil than for clay soil. Sandy soils will require more frequent watering, but for shorter periods of time than for a silt or clay soil.

Also consider the root zone of your plants, Jensen recommends. Small, closely placed annuals might need emitters spaced every four to 12 inches, whereas small perennials may need one emitter at each plant. Larger shrubs should have an emitter placed every two or three feet in a circle around the base.

"The object of a drip system is to keep soil moisture at an optimum level for plant growth," Jensen said. "It takes testing to find the right design and running time, and the system needs to be adjusted to accommodate growing root zones and changes in air temperature and rainfall."

More information about drip irrigation is available online in the OSU Extension publication "Drip Irrigation – An Introduction," (EM 8782) available online.

Other OSU Extension publications on watering are online:
"Conserving Water in the Vegetable Garden" (EM 8375) and
"Growing Your Own: Watering Your Garden"

A short video, "Soaker Hoses for Everything," and others on sustainable gardening can be found on the Sustainable Gardening Media page.

Author: Judy Scott
Source: Lynn Jensen