New methods grow bigger onions on better land

December 30, 2002

ONTARIO - Jumbo. Colossal. Super colossal. The superlatives used to rate Treasure Valley onions suggest they could take over the world. And in a way, they have.

After 15 years of research, scientists at Oregon State University's Malheur Agricultural Experiment Station have helped Treasure Valley onion producers triple their acreage in onions while at the same time reduce water use, pesticides, fertilizer and runoff.

And, in the process, the onions just got bigger.

Many of the onions sold in U.S. grocery stores during the fall and winter, and those served as blossoms and rings in restaurants, come from this valley at the border of Oregon and Idaho.

Clint Shock demonstrating the drip irrigation system in an onion field.Innovations developed by the OSU research station in partnership with growers and industry not only cut water and fertilizer use by half, they also produced crops of the very largest onions, rated "super colossal" and highly valued by the food industry.

But the story wasn't always this sweet.

Back in the mid-1980s, years of tractor-operated cultivation had compacted onion fields in Treasure Valley. Traditional furrow irrigation was sending lots of water, fertilizer and pesticides across the surface of fields, and beyond. Nitrate and residues of the herbicide DCPA seeped into groundwater.

"We could see regulations were coming down the pipeline, so we had to do something," said Clint Shock, superintendent of the OSU research station, appropriately located on Onion Avenue in Ontario.

Shock experimented with drip irrigation to replace the old furrow system and found the new approach could seep moisture and fertilizer slowly right to the root zone. With less water flowing over the surface, drip irrigation kept topsoil in place and protected water quality. And, with no water splashing onto onion leaves, chances of disease were reduced.

"A well-designed drip irrigation system will lose practically no water to runoff," said Shock.

But the research efforts did not end there. The experiment station scientists developed tests of soil and tissue to determine how much nitrogen the growing onions needed and when to apply it. They developed timing systems that released water only when sensors indicated that soil moisture had dropped below a particular level. At the same time, growers replaced DCPA with other herbicides that would break down more quickly.

With water and fertilizer dripped directly to the roots in measured amounts - and only when needed - onions grew large and well-centered, perfect for making onion rings.

"A large part of the onion improvement can be credited to breeding programs by private seed companies," said Shock, who works closely with Treasure Valley growers and industry, testing new onion varieties and developing innovative ways to grow them.

Results are measurable beyond the onion fields.

"Fifteen years of groundwater sampling indicates that residues of DCPA are decreasing in most places in the valley," said Shock, "and nitrate residues are no longer increasing, despite the three-fold increase in onion production."

Author: Peg Herring
Source: Clint Shock