(Wines&Vines) - With little relief from the ongoing Western drought on the horizon—or in the weather forecast—the wine industry continues to grow more interested in reducing and improving water use.

To address that interest, the Sonoma Resource Conservation District, Sonoma County Winegrowers and other agencies held a vineyard irrigation efficiency and water quality management workshop May 20 to provide growers with the best and most up-to-date information about water use and regulations.

Mark Greenspan, principal with Windsor, Calif.-based Advanced Viticulture, discussed the technology and methodology he uses to reduce overall irrigation water while increasing irrigation efficiency and improving grape quality. The session took place at Benziger Family Winery, which has become well known for its Biodynamic and sustainable vineyard practices. The winery, which includes 100 acres of vineyards, is also one of Greenspan’s clients, and during a vineyard demo that was part of the event he estimated the Benzigers have reduced their water use by as much as 40% in the past few years. 

Greenspan told an audience of about 100 growers he’s convinced that unless someone is dry farming, he or she can irrigate less frequently. He said he now usually recommends irrigating at 20% crop evapotranspiration, and 60% is not really deficit irrigation in his opinion.

However, he stressed it’s unwise for growers to irrigate at that level unless they are using soil sensors as well as a porometer and pressure bomb to accurately determine a vineyard’s level of soil moisture and plant stress.

He said right now vineyards in the North Coast still have sufficient soil water from winter and spring rains, and growers should wait and let the vines soak all that up before applying irrigation water. A little irrigation to add fertilizer is fine, but Greenspan said waiting forces the vines to send their roots deep in search of all available water. “Really that means waiting in the spring time and sometimes in the summer,” he said.

Greenspan said he doesn’t expect to apply regular irrigation this season at least for another six weeks to two months.

For monitoring soil moisture Greenspan uses an AquaCheck probe that measures soil moisture through relative permittivity and can either be checked manually or linked to a weather station to transmit data. The probes cost about $950, and when asked about where to place them, Greenspan said it’s best to locate one at the weakest point of a vineyard to provide a control point for irrigation.