Salinity, water use, and drought tolerance took front row seats at this year’s annual Viticultural Research Roadshow in Fresno, Calif.
“Do we want to save our soils or save our water?” was the rhetorical question posed by Mark Battany, University of California (UC) viticulture and soils farm advisor with San Luis Obispo and Monterey counties.
The two are inextricably linked, he explains, inasmuch as water plays a role in moving salts out of the root zone. The use of well water high in salts contributes to soil salinity.
Battany studied salinity and its impact on grape vines in the Paso Robles area and found a steady increase in salinity from 2006-2012 which heightened soil electrical conductivity and reduced fruit yields.
Salinity can result from restricted drainage and no leaching of the root zone, he says. Even with occasional leaching, some salts can accumulate and impact vineyard performance.
Salinity can degrade soil structure and hamper nutrient availability. Battany’s research indicates each season of irrigation water applies about 775 pounds of sodium per acre and about 3.1 pounds of boron per acre.
Another viticulture roadshow speaker shared the importance to test soils and water, correct drainage problems, adjust water chemistry as needed, apply gypsum or acid as needed, leach with irrigation water when rainfall is insufficient, and use tolerant rootstock varieties.
Battany says gypsum helps displace sodium and counteracts bicarbonate.
UC, Davis Grape Breeder Andy Walker says Ramsey is a salt resistant rootstock, but still better are St. George and 140 RU. Selections of acerifolia, arizonica, doaniana, and girdiana are better yet.
Walker says researchers are looking into the genetics of salt resistance in V. berlandieri.
Plant material from the nation’s Southwest has been a source of resistance to drought and salt. Some sources of vines previously found in the wild have virtually disappeared and some species do not lend themselves to propagation.
The salt resistant root stocks Dog Ridge and Ramsey are less available, Walker says, but have high vigor and strong nematode resistance. The 140 RU has excellent drought tolerance and moderate resistance to root knot nematodes, but it is not available and hard to propagate.
St. George has moderate drought resistance, is easy to propagate and is available, but lacks nematode resistance.
Walker flashed a slide showing the species V. candicans that grows vigorously, has plentiful roots, but is massive. At 80-feet tall, it dwarfs a person standing in front of it.
“Be careful what you wish for,” Walker quipped.
V. rupestris has been a source for relatively drought tolerant varieties, says Walker, which include - in addition to St. George - 1103P and AXR#1 (3309C).
“But site trumps all,” Walker said. “It depends on soil depth, rainfall, soil texture, and the water table.”
At the roadshow - presented by the San Joaquin Valley Winegrowers Association - growers and others also heard from Larry Williams with the UC Davis Department of Viticulture and Enology. He shared tips on irrigation, particularly during a drought.
“Know how much water you apply” was Williams’ overriding message. “Put a water meter in the drip line.”
He says growers need to ensure irrigation systems are maintained, know the evapotranspiration rates of vineyards, and assess vineyard soil water or vine water status.
Very dry soil can delay shoot growth once bud break has occurred. Williams advocates applying irrigation water just prior to or at bud break, if needed.
The closer the row spacing the greater the water use. He says ground cover use can require up to 40 percent more water. For lighter soils, he recommends irrigating more frequently with lowered amounts.
Williams distinguishes between regulated deficit irrigation and sustained deficit irrigation. The latter involves knowing the full evapotranspiration rate of a vineyard and purposely applying a proportionately lesser amount through the growing season.
Regulated deficit irrigation involves purposely creating water deficits at specific times during the season while minimizing or eliminating negative impacts on yield or crop revenue.
Larry Bettiga, UC viticulture advisor for Monterey, Santa Cruz, and San Benito counties, discussed trellises and canopy management. Both are important to growing high quality grapes, have high productivity per acre, and to have an efficient to farm vineyard.
Heavily shaded canopies can result in lower bud fruitfulness, Bettiga says, adding that interior leaves have lower rates of photosynthesis. For the fruit itself, too much shade can lead to lower sugar accumulation, lower anthocyanin and phenolic compounds, higher titratable acidity, higher pH and potassium, more fungal disease problems, and the slower loss of green, herbal, or vegetative characteristics.
“Fruit needs exposure to light,” Bettiga said.
Various trellis options address canopy management and to move harvesting and pruning equipment into the vineyard. Bettiga said managing fertilization and irrigation is important to provide the best canopy.
Representatives of two companies, Ranch Systems and PureSense, discussed systems they have available for monitoring water use and other activities.
David Jamison with PureSense says sensors used in the field can deliver data wirelessly on field conditions and applied water. The system gathers information used to answer the challenge posed by Williams - “Know how much water you apply.”
Mike Bauer with Ranch Systems said the company has systems for monitoring weather and climate, delivering alerts, soil moisture tracking, irrigation and equipment control, and tank and pond monitoring, in addition to remote cameras.
Jake Soberal, CEO of Bitwise Industries in Fresno, discussed the company’s development of a technology hub that could take a page out of the Silicon Valley handbook. At two locations in Fresno, Bitwise brings together representatives of 24 small companies and like-minded students or practitioners of new technology.
The company, says Soberal, can assist farming operations and others to build websites, adapting mobile applications, and marketing.
He said a “brochure type” website can cost as little as $2,000 to establish. A site with more functions can cost $5,000-$10,000.