Jan 17, 2012

Drip irrigation frees up more land for Idaho growers

Onion growers are continuing to increase their reliance on drip irrigation in southwest Idaho, according to Mike Thornton, the superintendent of the Southwest Idaho Research and Extension Center in Parma.

Thornton estimates that about 30 percent of onion acres in southwest Idaho, commonly called the Treasure Valley, use drip irrigation and that the number of acres is increasing at a rate of 5 percent annually.

There’s some real advantage to water and fertilizer use, Thornton said, and it really helps rotation because growers can go to new fields that haven’t been able to grow furrow-irrigated onions before because of too much slope.

Thornton said that current research is seeking to increase pest control in drip irrigation systems by testing insecticides currently labeled for foliar application use with onion. There are a couple of new insecticides labeled for foliar applications that they are presently testing to see if they could also be labeled for drip application. His current research is determining the best time to use the pesticides and how many applications should be made.
According to Thornton, there are three pesticides registered for drip irrigation for onion thrips: Vydate, Lannate and Admire.

An additional advantage with drip irrigation is less worker exposure in the field during pesticide and insecticide applications.

“We have less environmental exposure because we’re putting it in the small zone of the root system and you’re getting to the part of the plants where the thrips tend to concentrate,” Thornton said.

Clinton Wissel, president of the Idaho Onion Growers Association, supports Thornton’s assessment of drip irrigation opening up new land for onion production.

Because of drip irrigation, Wissel said he was able to extend his farming operation onto land that previously was too uneven for onion production. He estimates that he’s been using drip irrigation for about eight years. He uses drip irrigation on all 80 acres of his onion fields.
Other benefits of drip irrigation Wissel cited were water conservation and decreased use of fertilizer.

Wissel estimates his water savings using drip irrigation at 30 percent.

The only downside to drip irrigation is that taking up the lines every year can be time consuming, Wissel said.

Jim Klauzer, a sales agronomist for Clearwater Supply, has been marketing drip irrigation for 15 years. During that time, he’s seen a steady increase in drip irrigation practices in southwest Idaho. He estimates that more than 30 percent of all acres currently planted in onions are drip irrigated.

“The big advantage is uniformity of the crop. If they’re growing jumbos for processing, a high percentage will be jumbos,” Klauzer said.

Whereas, if you rely on furrow irrigation, you may end up harvesting 25 percent of four different onion sizes, Klauzer said.

“Packers are willing to pay a premium when they can be delivered a uniform product,” he said.

Besides uniform size of the crop, other advantages with drip irrigation include water savings of 30-35 percent, fertilizer bills cut by as much as 50 percent and the improved efficacy of pesticide application via drip irrigation.

Klauzer estimates that total cost for switching to a drip irrigation system runs about $1,200 per acre, depending on the economy of scale of the installation.

There are four components that go into a drip irrigation system. A pump station, a filter station, a distribution station and the drip tape.

Typically, the pump and filter stations are built on a trailer for relocation purposes. The drip tape is buried with the crop when it is planted.

Klauzer said the four components cost about $300 each. He estimates that the pump and the filter station average a 20-year lifespan, the distribution hose and valves are good for eight to 10 years and the drip tape is an annual recurring cost.

The shift to a drip irrigation system requires a higher level of management, Klauzer warned. You’ll want someone who knows the technical aspects of monitoring the system.

“It’s a shift from labor emphasis to management emphasis,” he said. “You need someone to operate a controller and do moisture management.”

By Bill Schaefer, Contributing Editor