PULLMAN, Wash. — 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 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, Wash. and around Prosser, Wash.

Sankaran said results indicate that using sub-surface irrigation, growers can use 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,” said Sankaran.

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 because 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 by only using 15 percent of the water normally used in vineyards, the vines still produced 70 percent of the amount of grapes typically produced.

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

In addition to saving water, Sankaran said the sensors can save growers time. Instead of walking through acres of crops and taking notes, a drone with the sensors can just be flown over the land.

Jacoby and his research team compared results of their method of measuring plant’s stress, which is relatively time intensive, to using the cameras. He said the results indicated the sensors provided the same information in less time and allowed researchers to measure the whole vineyard, instead of isolated plants.

Jacoby said the focus on saving water increased after the drought in California in 2015. That year was also the hottest and driest year on record in the state, which heavily impacted agriculture, he said.

Jacoby said he plans to eventually test his irrigation method on hops and some tree fruits in the state.

“We think that this does hold promise,” he said.