OREGON STATE UNIVERSITY

Drip irrigation attracts strong interest in Eastern Oregon

12/18/2000

ONTARIO - Drip irrigation is catching on in eastern Oregon as more and more growers look for cost effective ways to improve crop quality.

This year 1,000 acres of onions were grown with drip irrigation in Malheur County, according to Clint Shock, agricultural scientist at Oregon State University's Malheur Experiment Station near Ontario. Growers in the area are switching to drip irrigation because it promotes uniform growth of very large, high quality onions and it's more water efficient than furrow irrigation or sprinkler irrigation.

"Onions rated as super colossal are the biggest and most valuable," said Shock. "Onions with diameters greater than 4 3/8 inches and with single centers are very popular with the restaurant industry and with food processors because they are ideal for making onion rings" and other specially prepared restaurant menu items - like deep-fried "blossoms" - that require a large, well-shaped onion.

Drip irrigation is effective at producing good yields of super colossal onions because the system can be managed to deliver moisture directly to the plants' root zone at a uniform rate throughout the growing season, which allows the best possible growth, Shock explained. Liquid fertilizers can be injected into the system and distributed to the plants through the drip irrigation lines, he added.

In addition, there is little if any soil erosion in drip irrigated fields because there isn't any water flow on the soil surface. This helps conserve topsoil and protects water quality.

A drip irrigation system consists of lengths of drip tape buried a few inches deep in the soil beneath plant rows. The drip tape is a sort of flat plastic hose with emitters (specially designed perforations) every few inches to allow water to gradually seep into the soil.

The drip tape lines are attached to a water pipe at one end of the field. Water pressure in the system is maintained at a constant level to ensure a uniform flow of water to the crop. At harvest the drip tape is taken up and discarded before the crop is removed from the field.

"Using drip irrigation systems with onions has been one of our major research initiatives and so it's good to see more growers adopt the practice," said Shock.

In recent years researchers at the Malheur Experiment Station have evaluated different water application rates in drip irrigation systems, tried different fertilizer rates, and studied the performance of different onion plant population levels under drip irrigation.

Lynn Jensen, Extension agent in the Malheur County office of the OSU Extension Service, has worked closely with growers interested in drip irrigation and with Shock on drip irrigation studies. "This is wonderful technology and the future is bright for drip irrigation, but growers here will probably get into it gradually," Jensen said.

"There's a pretty steep learning curve with drip irrigation," he added. "In the first year or two growers may not wind up with as good a crop as they anticipated because they apply too much water and fertilizer. It takes time to learn how to operate the system for maximum results in the field."

Farrell Larson, owner and operator of Larson Skyline Farms near Ontario, agrees. He recently set up a drip irrigation system in a 380-acre field of onions.

"There are a lot of things you have to get used to with a drip system," Larsen said. "For example, you have to decide what type of drip tape to use, what type of emitters to use and what your flow rate should be."

But the benefits are worth the investment in time and money, Larsen added.

"You use about half the water and half the fertilizer you would use in a furrow irrigation setup," Larsen said. "If you operate a drip irrigation system properly, the moisture and fertilizer you introduce to the soil never leaves the root zone. All of it is used by the plant."

According to Shock, studies of drip irrigation on onions are continuing at the Malheur Experiment Station and the station is now looking at drip irrigation on potatoes and alfalfa for seed.