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Air quality chapter added to SWP guide

A chapter on air quality is being added to the workbook for the Code of Sustainable Winegrowing Practices (SWP) as California wine grape growers continue to support social responsibility and environmental stewardship.

Joe Browde, IPM program manager for the California Sustainable Winegrowing Alliance (CSWA), outlined the new chapter to growers and others at a recent Central California Winegrowers gathering in Madera.

The addition will deal with ozone and nonparticulate matter, greenhouse gases, and other issues that impact air quality.

“We want to develop the practices that will show regulators we are able to do a good job in mitigating these issues. This industry is a shining example of what can be done,” he said, adding that demonstration vineyards, workshops, and field evaluations will be presented for growers.

Hopefully, he added, the project also will be valuable in facilitating cost-sharing and incentive programs for conservation practices.

The 13 existing chapters of the 490-page document cover topics including viticulture, management of soil, water and pests, ecosystem management, and energy efficiency.

Measurement system

A special feature is an integrated scientific measurement system to track the industry's progress in adopting the guidelines.

The SWP code's mission is to perpetuate sustainability of the state's vineyards and production of world class wines, while advocating responsible farming with environmental awareness and the best science available.

SWA was formed in 2003 by the California Association of Winegrape Growers (CAWG) and the Wine Institute.

“We try to balance practices that are environmentally sound, economically feasible and socially equitable with what you do in your vineyards,” said Browde. The industry's sustainability lies where the three overlap.

While the three principles provide a general direction for practices, they must be readily translated into everyday operations. That's why the various chapters offer guidance in the development of practices leading to their voluntary implementation by growers.


Participants use it as a voluntary self-assessment tool — not a how-to manual, a set of mandatory rules, or a rating system that can be used to judge individual operations. Individual information is confidential.

Writing of the workbook began in 2001, and it took 18-months to develop the chapters, Browde said. Some 1,250 growers and vintners submitted their practices, and more than 110 workshops have been held.

Once participants submit information on their practices, such as use of predatory mites or raptors, for example, and it is compiled, each receives a copy. “This enables us to capture a snapshot of what the California wine industry is doing,” Browde said.

Practices are displayed by averages for regions and statewide to provide a comparison for growers. In the case of predatory mites and raptors, it can help growers learn how to make those practices pay off in vineyards.

“It's not a perfect tool, but it's a wonderful quantitative system,” he said. “Then we can zero in on sources, learn where the education is needed, work with the experts in Cooperative Extension, and deliver the information where it is needed.”

Funded by grants

The effort is supported by grants, currently including $150,000 for IPM projects from the American Farmland Trust, $60,000 for ecosystem management from the National Fish and Wildlife Foundation, and $475,000 for air and water quality from the Natural Resource Conservation Service.

Browde said his project seeks to collaborate with grower groups and vintners to continue to improve sustainability practices.

Another subject covered at the Madera meeting was hang time, a center of controversy between growers and vintners.

Broadly defined, hang time amounts to leaving the grapes on the vine for a period of time after customary Brix levels are reached, the intention being to allow further ripening to achieve certain more-desirable flavors. Many wineries are specifying harvest at higher Brix levels.

Growers argue the practice is risky, since the grapes are exposed to fungal infections generated by wet weather conditions in the fall. Further, growers say if the fruit is left on the vine too long the sugar-to-acid ratio can become unbalanced.

More importantly, the longer the grapes remain on the vine, the less they weigh when harvested and the less the growers are paid for them.

Optimum Brix?

Growers also point out the optimum Brix levels for different varieties and locations have yet to be determined though research.

Turlock viticulture consultant Stan Grant was engaged by CAWG to review research literature on hang time and extended ripening. He said he could find no published reports directly related to those subjects.

On yield loss, however, Grant said various field observations over many years and several locations show a wide range of reductions in weight of fruit beyond 23 degrees Brix according to location, variety, and weather conditions. “There's a wide range and a lot of factors in it, so it is really hard to say.”

Water loss from desiccated berries, he added, does cause a substantial loss in tonnage.

Grant said many questions for additional research remain, including, in part, the relationship between the degree of over-ripening and fruit weight, environmental conditions during extended ripening, and berry size and water status at ripening.

For the moment, he said, CAWG is supporting local field studies in Central Coast, North Coast, Northern Interior, Sierra foothill, and Southern San Joaquin districts to shed some light on the effects of hang time on yield and on quality of fruit and wines.

Quality essentials

Grant offered three essentials for high quality wine grapes, regardless of location: a balance between fruit and foliage, fruit exposure to dappled or intermittent sunlight for development of color, and moderate water stress shortly after fruit set.

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