A new subsurface irrigation system is showing promise for slashing water usage in vineyards.
Many vineyards use drip lines that saturate the top layer of soil, making grapevines dependent on surface moisture. But Pete Jacoby, a Professor and Plant Ecologist at Washington State University, wanted to see if whether a subsurface system could put water deeper underground, forcing the grapevines to extend their root zones and stressing the plants slightly, which growers tend to do anyway before harvest. By extending root zones, grapevines would be able to access water deeper in the ground, requiring less irrigation.
He modeled the system on buried irrigation lines in the Midwest for row crops. Those lines are buried in trenches but tend to clog when they come into contact with soil. Burrowing rodents can also chew on and damage buried lines.
Jacoby’s system relies on overhead feeder lines already present in many vineyards. A ⅛-inch spaghetti hose goes from that feeder line into the ground where it connects to a pressure-compensated emitter that injects water into the soil at varying depths of 1 foot to 4 feet. The grower could customize the system to irrigate more or less depending on local weather and the amount of stress desired.
“We’re trying these at much deeper depths to create a dry zone beneath the vines,” Jacoby says. “The root system tends to be concentrated in the top 18 inches of the soil. We’re sort of hardening these vines up a little bit by cutting back on the amount of water these vines are receiving and forcing them to go deeper.”
The system is still in the proof-of-concept stage and trials are being held at a commercial vineyard. In 2015, using 60% of the water used throughout the rest of the vineyard, Jacoby’s experimental vines yielded 90%. At 30% of the water, they yielded 75%. And at 15% water, they yielded 70%.
Continued trials will help determine the best depths and amounts of water required to sustain high yields.
Jacoby says he recently received funding to also study grape quality with his irrigation system. He plans to submit grapes for testing this fall.
“If there are differences in grape quality, we will pursue additional funding to better quantify these factors that could lead to producing high-quality, premium wines with direct root-zone micro-irrigation,” he says.