Posts Tagged: viticulture
Study shows sugar, color content should be watched
Warming temperatures over the past 60 years have led to increased wine quality, but a new study looking at sugar and color content in grapes indicates the industry may be facing trouble if trends continue, according to collaborative research out of the University of California, Davis, and University of Bordeaux.
“Quality has increased steadily up to now,” said lead author Kaan Kurtural, a professor of viticulture and enology and an extension specialist at UC Davis. “We just don't know the tipping point.”
Kurtural's research, published in the journal OENO One, focuses on two renowned wine regions — Napa Valley and Bordeaux, France.
Researchers looked at ripening, grape quality and temperature data over six decades in both regions and then confirmed the findings with a five-year trial in Napa. They also consulted wine ratings in publications like Wine Spectator to gauge consumer demand.
One key finding: As temperatures exceeded what was considered the optimal level for quality, the grapes produced better wines.
“Previous research had few field data, but a record of assumptions,” said Kurtural.
Other quality factors at play
Temperature is a factor, but the paper suggests that sugar and color content should not be discounted. The authors also identified a biomarker that affects taste, color and other factors that can be the bellwether for climate change in red-skinned wine grapes.
“Temperature is always there,” he said. “Temperature is not your bellwether.”
Higher temperatures can harm grape composition, including color, taste and aroma. Researchers examined pigment and sugar content of five California vintages of cabernet sauvignon, finding that as the grapes got sweeter the skin and color deteriorated.
The degradation of these quality-related compounds and the observed plateaus of wine quality ratings suggests there can be too much of a good thing.
Researchers have long theorized that increasing temperatures from climate change would lead to shifts in wine-growing regions, opening up some new areas for vineyards and making others unsustainable.
That shift could be a boon to some economies and devastating to others, something the industry should watch.
“Since the 1980s, grapes got riper and they were able to make better flavor and color compounds,” Kurtural said. “Are we going to lose this or adapt more?”
Gregory A. Gambetta with the University of Bordeaux is a corresponding author on the paper.
For more information:
- Kaan Kurtural, Viticulture and Enology, cell 707-200-5378, firstname.lastname@example.org
- Amy Quinton, UC Davis News and Media Relations, cell 530-601-8077, email@example.com
- Emily C. Dooley, College of Agricultural and Environmental Sciences, cell 530-650-6807, firstname.lastname@example.org
Study finds using less doesn't compromise quality
California grape growers in coastal areas can use less water during times of drought and cut irrigation levels without affecting crop yields or quality, according to a new study out of the University of California, Davis.
The findings, published today (Sept. 1) in the journal Frontiers in Plant Science, show that vineyards can use 50% of the irrigation water normally used by grape crops without compromising flavor, color and sugar content.
It sheds new light on how vineyards can mitigate drought effects at a time when California is experiencing a severe water shortage and facing more extreme weather brought on by climate change, according to lead author Kaan Kurtural, professor of viticulture and enology and an extension specialist at UC Davis.
“It is a significant finding,” Kurtural said. “We don't necessarily have to increase the amount of water supplied to grape vines.”
Growers will also be able to use this information to plan for the next growing season. “Everybody's worried about what's going to happen next year,” he said.
Kurtural and others from his lab studied irrigation and cabernet sauvignon grape quality at a research vineyard in Napa Valley over two growing seasons, a rainy one in 2019 and a hyper-arid one in 2020.
They focused on crop evapotranspiration, which was the amount of water lost to the atmosphere from the vineyard system based on canopy size. The weekly tests used irrigation to replace 25%, 50% and 100% of what had been lost by the crop to evapotranspiration.
Researchers found that replacing 50% of the water was the most beneficial in maintaining the grape's flavor profile and yield. The level of symbiotic arbuscular mycorrhizal fungi, which help grapevines overcome stresses such as water deficits, was also not compromised. And the water used to dilute nitrogen application was also reduced, making the process more environmentally friendly.
The water footprint for growing grapes also decreased. For both the 25% and 50% replacement levels, water use efficiency increased between 18.6% and 29.2% in the 2019 growing season and by 29.2% and 42.9% in the following dry year.
While focused on cabernet sauvignon, most red grapes will respond similarly, he said.
“In the end, drought is not coming for wine,” Kurtural said. “There doesn't need to be a tremendous amount of water for grapes. If you over irrigate in times like these, you're just going to ruin quality for little gain.”
Members of Kurtural's lab — Nazareth Torres, Runze Yu, Johann Martinez-Lüscher and Evmorefia Kostaki — are also credited as authors.
University of California Agriculture and Natural Resources provided partial funding.
For more information, contact:
- Kaan Kurtural, Viticulture and Enology, email@example.com
- Amy Quinton, UC Davis News and Media Relations, firstname.lastname@example.org
- Emily C. Dooley, College of Agricultural and Environmental Sciences, email@example.com
A welcome sign of spring each year for grape producers is budbreak, the moment when tiny buds on the vine start to swell and green leaves appear. Budbreak varies by region, variety and even vineyard topography, but in Sonoma County, unseasonably warm weather caused buds to burst early, reported Bill Swindell in the Press-Democrat.
“Perhaps it's the new normal,” said Jen Walsh, the winemaker at La Crema Winery in the Russian River Valley, commenting about long-term change due to global warming.
The Carneros region that borders San Pablo Bay is typically the first wine appellation to experience bud shoots on grapevines, given its milder climate, said Rhonda Smith, UC Cooperative Extension viticulture advisor in Sonoma County. In addition, hillside vineyard areas in the county with south- and west-facing slopes also usually are on the early side because of their longer sun exposure.
There is a downside to early budbreak. The vines are susceptible longer to a potential spring frost, which could harm opening buds and young shoots.
Below are recent tweets heralding the 2020 budbreak around California.
The front-page story provided an overview of Jordan's career, research plans and personality.
“My love of wine drives a lot – what can I say,” Jordan said. “I don't know about you, but I want to keep drinking wine until the day I die, so I really want to do my part to ensure the sustainability of drinking California wine.”
As part of the project, Jordan is looking for grapevines that thrive in the valley heat, produce a large crop and develop berries with color, flavor and acidity needed for fine wines.
"I won't declare any winners," Jordan said. "I'll say I have favorites, and I definitely have losers that I would not recommend.
The project was started by James Wolpert, a retired UC Cooperative Extension viticulture specialist, and continued by Matthew Fidelibus, UCCE viticulture specialist based at Kearney. Jordan took over the project a year and a half ago.
Finding the next cabernet sauvignon or chardonnay would be a home run, Fidelibus said. However, the data supplied by the project are also important in providing farmers and wineries the research and background to expand their own vineyards.
“If any of these varieties are going to be useful, it's important that the wineries are interested and comfortable with them,” Fidelibus said. “The grower can't grow varieties without the assurance that a winery is going to use them.”
Recently, it seems we have reached a plateau of production with current planting materials and management methods in the San Joaquin Valley vineyards. Making a vineyard less variable with more uniformly productive grapevines regardless of their location within a given vineyard is the most important question to the viticulturists.
Vineyard variability was first studied in Australia, and the yield variation within-vineyard is typically of the order of 8 to 10 fold . The fruit quality variation might follow the similar pattern as yield variation under or over a certain crop load window. Differential harvest was first applied in Australia with yield monitor installed on the mechanical harvesters to separate the low yield zone and high yield zone for high quality and low quality fruit for different wine programs. It was an improvement from the winemaking point of view. However, differential harvest still didn't solve the problem of vineyard variability for both yield and quality. Then viticulturists started to think of differential management or even differential planting may provide a solution to variation in vineyards.
Then the question becomes: is the variation pattern always consistent? Unlike annual broadacre crops, e.g. corn or soybeans, grapevines are a perennial crop and the yield variation carry-over effect is always something important for viticulturists to keep in mind. Initial research results suggested the variation pattern can be consistent in 2 years' period. However, different site location may contribute to vineyard variation as well. Soil texture, water holding capacity, and soil mineral nutrient content were believed to be the main cause of the variability. Further investigation is needed to confirm that the variation pattern is somehow consistent and manageable to make the vineyards produce uniformly.
Once it is assessed vineyard variability can be managed. Defining vineyard variability becomes the next question. Assessing vineyard variability visually may not be possible for large vineyards. Yield monitoring, on the other hand, is only suitable to define the variability at harvest and might be also financially difficult for small growers. Early detection of the vineyard variability in order to manage the vineyard differentially is an active area of research. Currently, different sensors have become available for vineyard managers to tell how much variability is in the vineyard through measurement of canopy reflectance through use of NDVI, thermal images, irrigation scheduling using sap flow sensors and availability of soil moisture through measurement of soil matric potential. UAVs and satellite imagery are also available to assess vineyard variability at an economical cost, as they may provide larger data sets with relative cheap cost. However, ground-truthing is needed to make sure how accurately these data from different sensors define the variability in the vineyard.
Recently, Cornel University, Carnegie Mellon, and UC Davis were awarded a $6 million grant from the USDA's Specialty Crop Research Initiative (SCRI) to further study the proximal sensing, crop estimation, and soil mapping to develop tools for variable rate management in table and wine grape vineyards. The goal of the project is to increase/optimize yield and quality within a vineyard by spatially tuning (a) vine balance and (b) canopy light microclimate.
The challenge for San Joaquin Valley grape growers is to make grape growing more economically sustainable for future generations. Optimizing yield per acre with less labor and energy inputs should be the goal of growers. Reducing the vineyard variability to have more uniform production might give growers more profit per acre by increasing the yield per acre without adversely affecting fruit quality. Ultimately, new breeding materials will be the long term goal to increase the yield potential and profitability for vineyards.