A number of research topics specific to wine and raisin grape production in the San Joaquin Valley were discussed at the San Joaquin Valley Winegrowers Association’s second annual Viticultural Research Road Show in Fresno earlier this summer.
The day-long event featured research reports from a number of prominent viticulturists on topics ranging from insect, weed and water management, to vineyard mechanization and clonal selection.
The second annual road show this year paid tribute to Robert Wample, recently retired Julio R. Gallo Chair of Viticulture at California State University, Fresno. Prior to receiving a special award, Wample pondered the future of wine grapes in the San Joaquin Valley, and urged growers to find innovations for addressing big-picture topics, such as global market shifts, climate change, and urban growth.
“Do everything you can to learn to be proactive,” he said. “Figure out where things are going locally, nationally and internationally, and be proactive.”
Being proactive means absorbing and integrating state-of-the-art research into viticulture operations.
Association Executive Director Peterangelo Vallis said the road show aims to bridge the gap between academics and practical application to help growers in the Valley do just that.
Fresno State’s Bronco Wine Co. Viticulture Chair S. Kaan Kurtural shared the latest results of an ongoing, multi-year research project on mechanized vineyard systems in San Joaquin Valley winegrapes. The commercial mechanization trial goes beyond mechanical box pruning and hedging to include mechanical pruning, shoot thinning and cluster removal to replace costly hand practices.
“A key component of this program is to implement a balanced pruning and thinning system in less time that it would take to cover large acreage by hand,” Kurtural said. “Research has shown this can be achieved on the Central Coast so we wanted to know if it could work in the Central Valley.”
The multi-year trial started on a 10-acre drip-irrigated Cabernet Sauvignon vineyard at Fresno State, planted under 12-by-7 foot spacing on east/west facing rows with a California T trellis. Four individual blocks compared three treatments, including conventional hand pruning and thinning; mechanical box pruning with hand cleanup; and mechanical box pruning with mechanical thinning and brush pruning.
For the last two years, the trial has shown that both mechanical and hand pruning approaches brought similar results in yield and wine grape quality with only subtle differences. Kurtural recorded no differences in the number of berries per cluster, raichis length uniformity and cluster tightness. The mechanical approach, however, did cut down on vigor, berry size and volume, and there were notably more anthocyanins in the juice on fully mechanical blocks, which can an important wine characteristic factor.
“Yield components were not affected, but the anthocyanins were 20 percent higher with the mechanical approach,” he said.
On the economics, Kurtural said mechanical canopy management provided significant labor cost savings over hand pruning and thinning, averaging 50 cents per vine to hand prune and thin, 42 cents per vine to box prune and hand cleanup and 30 cents per vine for full mechanization.
“Complete mechanization cut down the cost per vine by about 42 percent, so that could be a significant savings if you have a large ranch,” he said. “Based on what we’ve seen in this treatment we have expanded the trial into a commercial vineyard and are also looking at the effects of irrigation on this type of approach as well.”
The expanded commercial trial is exploring the effects of mechanization, crop load and regulated deficit irrigation on Shiraz grapevines to understand differences in yield, fruit composition and phenolics from these different practices.
An additional research presentation by Andrew McAloon of the USDA Agricultural Research Service is looking at sustainable water use in California vineyards and the use of dual heat pulse sap flow sensors to measure and automate data collection on vine stress.
“Water is a limited resource here in California and with decreasing quantities and more competition for water, we want to be able to quantify total water use and uptake patterns at specific locations,” McAloon said.
Sap flow sensors offer the best potential for getting real-time feedback on vine stress from irrigation systems to develop site-specific crop coefficients, he said.
Additional presentations included a practical guide to weed management in grapes by Fresno County Farm Advisor Kurt Hembree. He urged growers to make post-emergent herbicide applications “on-time and on-target” to optimize viticultural weed control. He said growers should time post-emergent applications just as weed flushes occur for best control and apply herbicides under adequate spray pressure using proper nozzle size and type and shields as part of a best management approach to minimize drift and off-site movement.
“It’s best to treat small weeds,” he said. “Horseweed and fleabane are particularly tough to control so you want to hit them when they are small. If you want to control them you’ve got to get it out early.”