Balanced Vines Produce Better Wines

Researchers share findings about correlation between yields and wine quality

by Paul Franson
wine grape vineyard napa yields rootstock
Speaker Nick Dokoozlian of E. & J. Gallo said that dropping green fruit can speed maturation but causes no substantial improvement in quality at harvest.

Napa, Calif.—The issue of “the lower yield the better” as a universal rule has been pretty well debunked by scientists, but it hasn’t been accepted by all winery marketing personnel (and some winemakers) who insist that lower yields equal better quality.

Further proof that this belief isn’t necessarily true was outlined in a seminar about finding the perfect balance at the Napa Valley Grapegrowers’ annual Rootstock conference held today at Napa Valley Exposition Fairgrounds.

The talk, “The Metaphysical Relationship Between Crop Load and Wine Quality,” did challenge some cherished beliefs, however, including the superiority of vertical shoot positioning as well as minimal yields.

The two speakers were Dr. Nick Dokoozlian of E. & J. Gallo Winery and Dr. Patricia Skinkis, viticulture extension specialist and associate professor at Oregon State University. The session was moderated by Caleb Mosley, senior viticulturist at Michael Wolf Vineyard Services.

Dr. Nick Dokoozlian is vice president of viticulture, chemistry and enology at E. & J. Gallo Winery. He is responsible for research and innovation in the areas of grape and wine production, including the development of growing practices that improve the yield and quality of grapes and wines, the development and application of grape and wine chemical quality metrics and the impacts of processing, fermentation and aging practices on wine composition and sensory characteristics. He also manages external research collaborations in these areas with universities and other research agencies.

Dokoozlian already was a well-known researcher at the University of California, Davis, when he joined Gallo, and his talk gave a rare look into Gallo’s extensive research. He referred to numerous studies during his talk.

Grape Quality Index
He stated that the relationship between crop load and wine quality is likely the most thoroughly studied aspect of grape and wine production, but a correlation remains unclear.  “It’s almost mystical. Up to now, we haven’t been able to find a way to measure it directly. There’s a lack of proper measures and metrics and a lack of accepted fruit standards.”

That didn’t keep Dokoozlian from developing a system that seems to have served Gallo well as it makes wines from inexpensive to luxury, however.

Dokoozlian noted that our ideas of quality and yield come from Europe (notably, France), where he says that historically the “low yield equals high quality” equation was true due to its climate, growing practices, plant materials and viruses, but it may not apply in California.

Gallo has a wide range of vineyards, and he said, “We can find vineyards with high yields and high quality, and we can find vineyards with low yield and high quality.”

The problem is that yield per acre does not integrate canopy capacity or vineyard management practices.

In an attempt to sort this out, Dokoozlian developed a Grape Quality Index that correlates wine quality to price tiers and other parameters. It judges negative aromas like green pyrazines, positive aromas like red, black or jammy fruit, depending on the variety, along with mouthfeel and correlates it all to pricing tier based on categories of IRI, the Chicago-based market-research firm.

Dokoozlian stressed that vine leaf area exposed to the sun per gram of grapes is critical. For Cabernet Sauvignon, for example, quality rises at a steep slope to 10 to 14 cm2/g, then little improvement occurs with more leaf area. Unfortunately, it’s difficult to measure leaf area except destructively, so pruning weights are a common alternative.

Not all varieties follow this pattern. Pinot Noir, for example, continues to increase quality with more leaf area but the slope of improvement is much lower (between 4 cm2/g and 8 or 9 cm2/g). Cabernet is less sensitive to crop load.

Dokoozlian devoted considerable time to crop thinning, in the process noting that shoot thinning also reduces potential leaf area. “In the short term it will reduce tons per acre, but it doesn’t improve quality. Thinning 20% or even 40% has little impact on quality. You have to remove 75% of the crop to have much impact.”

He added that dropping green fruit can speed maturation but causes no substantial improvement in quality at harvest.

The Gallo researcher is no fan of VSP trellising as a universal system, because it reduces leaf area exposed to sunlight. In tests, Gallo has found that split canopies are superior in many areas.

Dokoozlian concluded that balanced vines accumulate higher quality at lower Brix than over- or under-cropped vines. Unfortunately, Dokoozlian admitted that he’s not sure why this is true but speculates that an internal trigger limits sugar accumulation.

“You can achieve ripe flavors at 24º to 28º Brix with balanced vines instead of 28º Brix.” He stated, “Most Napa and Sonoma vineyards are undercropped.”

Yields for Pinot Noir
Following Dokoozlian’s talk, Patricia Skinkis of OSU discussed extensive trials conducted in that state on yield versus quality for Pinot Noir, which represents 62% of Oregon’s grape acreage The total acreage is only 28,000, compared to California’s more than half a million acres.

She noted that Oregon winemakers have typically demanded low yields, but believes the state could produce quality wines at higher crop levels.

The state’s average Pinot Noir yields have been 2.2 tons per acre during the past 26 years, but the numbers have risen of late. The harvests of 2014 and 2015 reached record highs with an average of 3.2 tons per acre, a level some winemakers reject as too high.

Skinkis has conducted crop load research in more than 10 commercial Pinot Noir vineyards of Oregon’s Willamette Valley for five years. The growers followed careful instructions and left between 0.5 and two clusters per shoot, plus a control.

Wines made with 0.5 clusters per shoot were vegetal, while the winemakers overwhelmingly selected 1.5 clusters per shoot as “optimal” in blind tests. Notably, the natural average is 1.8 clusters per shoot.

At any rate, there was little different in Brix, TA or pH in most sites with thinning. The biggest impact was on anthocyanins.

“You have to get to 30% or 40% reduction to have much impact,” Skinkis told the audience.

However, Oregon’s conditions are not like those of California vineyards.

Growers reduce fruit to hasten ripening before rains and decrease Botrytis as well as attempt to increase quality. But she noted that Oregon growers can never hope for the average fruit levels in California because of different climate conditions.

She concluded her talk with samples of Pinot Noir wines made different crop levels from two wineries in two years. Audience reaction was mixed, however, with tasters stating they preferred lower yields only after being told which was which.

In addition to this seminar, the conference featured other seminars by industry experts, vineyard and wine trials, networking opportunities and an exhibition featuring more 120 industry suppliers and services.



Posted on 11.09.2016 - 10:05:45 PST
Hmmmmm. Seems Sunlight Into Wine was right after all. Well said Nick and Patty.
Richard Smart

Posted on 11.11.2016 - 04:44:33 PST
Looks like there a lot of guys speaking without scientifical support....By the way I know Nick and can say he has the neccesary ones...
Javier Horacio Gancedo Guidugli