Thomas Clemens owner of Clemens Vineyard Equipment Inc discusses a box pruner during the vineyard mechanization workshop

Thomas Clemens, owner of Clemens Vineyard Equipment Inc., discusses a box pruner during the vineyard mechanization workshop.

Vineyard mechanization can help improve grape quality

Vineyard mechanization, which was spurred initially to cut the costs of production and labor needs, particularly in the San Joaquin Valley (SJV), can also be a factor in improved quality, says Jim Kennedy, chairman of Fresno State's Department of Viticulture and Enology. 

Vineyard mechanization, which was spurred initially to cut the cost of production and labor needs, particularly in the San Joaquin Valley (SJV), can also be a factor in improved quality.

This point was made in opening remarks by Jim Kennedy, chairman of the Fresno State University Department of Viticulture and Enology, and it wove its way through presentations during a workshop on vineyard mechanization and sensing on the campus.

It carried over into field exhibits of equipment, where Jon Holmquist, manager of grower relations for Constellation Brands Inc. in Madera, made this observation: “We’re getting our highest quality fruit off of machine-pruned, box-pruned vines.”

He said a high-yielding French Colombard vineyard in Madera that is mechanically harvested has better quality than grapes that are hand pruned.

Holmquist was not tempered in his enthusiasm concerning one of the prototypes on display, a box pruner from Clemens Vineyard Equipment Inc.

“I’m very interested,” he said about the equipment that will likely be priced in the mid-$40,000 range. “It would enable what he termed “one-pass, dormant pruning.”

A rare downpour the day of the workshop brought mud and soggy vines that prevented demonstrations of equipment at work, but it didn’t dampen the interest in equipment on display.

Flipped over weeds

Thomas Clemens, owner of Clemens Vineyard Equipment in Woodland, chatted with Holmquist and others about equipment that included the box pruner, a hedger, and a device for weeding the vineyard that undercuts roots of weeds and flips them over to exposure to the sun.

Others talked of machinery which thins leaves and removes shoots.

Before venturing into the vineyard, as rain pelted the campus, workshop participants gathered inside a building on campus to hear about the latest in mechanization.

Mechanization and raisin harvest

The opening presentation, by Matthew Fidelibus, University of California Cooperative Extension specialist at the Kearney Agricultural Research & Extension Center in Parlier, was a look at how mechanization of the raisin harvest has evolved over the years to a point where nearly half the California crop is mechanically harvested.

Fidelibus said a new dried-on-the vine variety is poised for release in 2016. The variety is called Sunpreme, developed by David Ramming, now retired from the U.S. Department of Agriculture’s Agricultural Research Service in Parlier.

Among its virtues, Fidelibus says, is that grapes dry naturally on the vine, and there is no need to cut the cane.

“It’s fruitful on the basal nodes, and there’s no need to cane prune,” he said. “It can be spur pruned. This means less labor for pruning and harvesting.”

Mechanization cost savings

S. Kaan Kurtural, Bronco Wine Co. Viticulture Chair and faculty member at Fresno State, addressed cost savings through mechanization and the importance of canopy management.

He discussed the need to manage sunlight reaching the fruit and keeping canopy growth under control to improve the quality of grapes, while at the same time ensuring high yield.

He said for red wine grapes that the incorporation of reduced deficit irrigation is a key to building color and retaining it.

Kurtural addressed the delicate balancing act that comes with sunlight exposure. The idea is to maximize diffuse or indirect sunlight within the canopy and to minimize exposure of fruit to direct sunlight, which is especially important in the heat of the central SJV.

To burn up green flavors, he said, “Early season exposure is the only thing that works. To increase fruity, jammy flavors, Kurtural says late season exposure will enhance them, but might decrease yield due to shriveling.

For white wine grapes, he says crop load management is more of a key than canopy management. He added that canopy and crop load management can be done through shoot thinning, cluster thinning, and leaf removal.

Kurtural says unbalanced vines form large canopies, have high water demands, set fruit of inferior quality, have higher green flavors, and have lower fruit flavors.

Leaf removal timing

Leaf removal, he says, is best done one week prior to bloom, resulting in increased concentration of anthocyanin and flavonol. Post-fruit set removal results in higher astringency.

Anita Oberholster, a UC  Cooperative Extension specialist in viticulture and enology, discussed research which shows that mechanical harvesting of wine grapes has “inconsequential” effects on wine quality and that those who taste mechanically produced wine and hand-picked wine have no strong preference.

She points out that while mechanical harvesting is much faster than hand harvesting, it is resisted by some due to berry damage, the inclusion of material other than grapes, increased microbial and enzymatic activity, and the loss of juice.

Yields, however, can be increased with mechanical harvesting.

Oberholster found that sorting helped in the removal of raisined grapes, leaves, twigs, bugs, unripe and damaged fruit, grass clippings, and bits of stems. But it was not essential with mechanical harvesting, she said.

While SJV producers of wine grapes wrestle with improving quality, they also often face lower returns on grapes produced there when compared with other regions of the state.

As an example, more than a third of the state’s Merlot grapes are crushed in the SJV and the average grower return for those grapes is about $375 per ton, compared to a statewide average of about $775 per ton.

Serhat Asci, a research fellow with the Fresno State Center for Ag Business, said wine grape color traced to anthocyanin is a factor in the differential, adding that the valley is noted for low accumulation of anthocyanin.

He said leaf removal and deficit irrigation stepped up levels of anthocyanin and improved color. Yet they reduced yield, particularly in drought conditions.

However, Asci says such treatments improve wine quality and could increase the negotiation power of growers.

Gleaning info from above

Workshop participants also heard Bob Westbrook, vice president of TerrAvion in Dublin, Calif., talk about the value of information gleaned from the air above to manage farm land.

TerrAvion uses fixed wing aircraft operated by flight schools to gather information on what is happening in the field. He said it’s cheaper and less time-consuming than what can be gleaned by “a dude and a drone and pickup truck.”

“Everything changes every week and management can’t see it” without the over-flights that can provide a terabyte of data each day, Westbrook said. The company flies over 120 ranches in the Napa-Sonoma area.

From the air, Westbrook says a pest problem can be found, a need to boost irrigation, and “what should be treated and harvested.”

It’s not a simple process, he emphasized, adding that the traits of different varieties can bring varying demonstrations of stress levels.

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