PULLMAN — Washington State University researchers are seeking new ways to increase efficiency of water use in agriculture.

Associate Professor Sindhuja Sankaran is working on using specialized sensors to measure heat stress in grape vines as a way to test the effectiveness of sub-surface irrigation.

“It can see things beyond what we can see,” she said.

The sensors use infrared technology used to determine if plants are receiving enough water, or if they are under too much heat stress. The first round of trials took place last year near Benton City and around Prosser.

Sankaran said results indicate that using sub-surface irrigation, growers may lower usage to only 60 percent of the amount of water typically used, without over stressing the grapes, affecting quality or decreasing yield.

“If in the second season we see the same thing, that means you can save 40 percent water,” Sankaran said.

Sankaran is working with WSU Professor Pete Jacoby to determine the effectiveness of Jacoby’s technique for sub-surface irrigation. The system is set up with plastic tubes going into the ground, near the roots, at depths varying from 30 cm to 120 cm.

Jacoby said having the water come from deeper in the soil forces the roots to go deeper, making the plants more drought resistant.

This method differs from other methods in which irrigation systems are buried. The water is distributed lower, and the water emitter is located above the ground.

Jacoby said buried drip irrigation tends to clog because of the direct contact with the soil. He also said animals such as gophers have a tendency to chew on underground emitters.

Keeping the water lower in the ground prevents weed growth and limits evaporation, all of which lead to greater efficiency of water use, Jacoby said.

“We think that we can increase water use efficiency by at least 50 percent of what it currently is, by putting the water below the surface,” he said.

Jacoby said that while using only 15 percent of the water normally used in vineyards, the vines still produced 70 percent of the amount of grapes typically produced.

Sankaran said that, in the coming season, she and the other researchers will focus on yield and quality. Trials will begin this year when the season starts, sometime around the end of May or early June, she said.