- Onions On Drip
Oregon Researchers Look at Irrigation Methods
By Karen Gentry
Managing Editor
After comparison of drip, sprinkler and furrow irrigation of onions in Oregon and Idaho’s Treasure Valley, sub-surface drip came out on top.
These tests were done in the early 1990s on sites that didn’t irrigate perfectly, according to Clint Shock, superintendent of the Oregon State University (OSU) Malheur Agricultural Experiment Station in Ontario, Ore. Treasure Valley includes about 750,000 acres of irrigated land within a 50-mile radius of Ontario, Ore. (East-Central Oregon) and four counties of Idaho.
“The main advantage (of drip irrigation) is you can irrigate a field absolutely uniformly, so you can apply fertilizer absolutely uniformly and with great efficiency,” Shock said.
“The grade of the onion comes out really nice. You can get a really
uniform crop so the whole field is all the same,” he said.
He said research also looked at irrigation criteria for drip-irrigated onions, nitrogen fertilizer rates for drip-irrigated onions and detailed work on the ideal plant populations for drip-irrigated onions.
OSU researchers found that with drip irrigation, moisture and fertilizer seeps slowly right to the root zone. Drip irrigation keeps topsoil in place and protects water quality. Less water on onion leaves lessens the chances for disease.
Shock said that drip tape in onion beds makes strategic applications easier.
“The disadvantage of drip system is the added cost,” said Shock. He said the expense is easily made up in many cases. “A field with a variable grade you’ll get a better crop with drip irrigation,” Shock said.
Researchers at the Malheur station also use soil moisture sensors for furrow-irrigated and drip-irrigated onions to optimize yield and grade. Shock reported that residues of the herbicide DCPA (trade name Dacthal) are decreasing in the Treasure Valley groundwater, through the adoption of other herbicides that are applied in very small amounts.
“A key part of implementation of drip irrigation work has been innovative drip irrigation applications,” said Shock. He said Brian Anderson and the employees from Clearwater Supply, in Othello, Wash. have been instrumental in getting drip irrigation applied and installed in growers’ fields. “Clearwater Supply has been a leader in taking drip irrigation for onions and helping growers actually make it work in their field,” said Shock.
Reid Saito, with KLG Farms in Nyssa, Ore., said most growers still use furrow irrigation, as drip irrigation is in its infancy. “If we keep our current ground we wouldn’t have to change (to drip irrigation). If our water situation changes, if water supply is tighter, we might look at switching over to drip,” said Saito, who is president of the Malheur County Onion Growers Association.
Saito said that as researchers and growers build on the knowledge about drip irrigation, more growers will switch over. He noted that there is a learning curve for growers with drip irrigation.
As the area receives scant rainfall—fewer than 10 inches per year—irrigation has been around since the first pioneers. With furrow irrigation, onion growers rely on water reservoirs for this surface irrigation.
Saito uses a laser leveler so that the slope is pretty consistent or even. “Onions require a high percentage of water but they don’t have a real deep root systems. You have to be careful on how you water,” said Saito.
Japanese-Americans started growing onions in the region in the 1930s, Shock said. Today family farmers in Treasure Valley produce onions on 20,000 acres. Shock said it is fairly common for growers to have about 40 to 800 acres.
Most onions produced in the Treasure Valley are yellow sweet Spanish cultivars. The onions are marketed fresh from August through October, and they’re shipped from August through March with natural air storage and some refrigerated storage. Although the region’s onions are shipped across the United States, the primary markets include the Northeast and the northern Midwest.
Although open pollinated sweet Spanish varieties were the standard in the region, hybrid cultivars gained popularity in the last two decades. The hybrids are more uniform and higher yielding.
Saito grows primarily the Spanish sweet yellow varieties with a few red and white onions on 180 acres. “We try to get everything harvested by the end of September,” Saito said.
Saito is a part owner of Snake River Produce in Nyssa, Ore. He said there are more than 200 growers on the Oregon side and 200 growers in Idaho who are a part of a federal marketing order.
The Idaho-E. Oregon Committee is a non-profit organization that was formed in 1957 and represents the interests of growers and shippers. In order to be labeled “Idaho-E. Oregon,” onions from this growing region must meet the strict quality regulations of Federal Marketing Order #958.
“I think it (marketing order) gives us an advantage. Every load that goes out has to have inspections,” said Saito. He said most growers are pleased with the marketing order that standardizes the grade of onions. Growers pay an assessment according to what’s packed and shipped per cwt. The assessment varies from year to year, but it’s mostly in the nine to 10-cent range, Saito said.
The assessment also supports the three committees: research, export and promotion.
