By Sam Jones

​Grape growers in Napa County are constantly looking for innovative ways to decrease waste while increasing productivity in their vineyards, but not all of these methods are high-tech or brand-new. For many, the act of accumulating, turning and spreading compost is a basic but key part of their vineyard management strategy, and has been practiced since ancient civilizations first prioritized agriculture.

“Composting has always been considered key to better farming and is a key practice employed in Napa Valley vineyards,” said Michael Silacci, winemaker for Opus One and president of the Napa Valley Grapegrowers. “When composting is done properly using good management techniques and temperature monitoring, the result is a fine source of nutrients for plants and it has a positive impact on preventing soil erosion by rebuilding soil structure and supporting plant growth.”
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By increasing microbial activity in these waste materials – think oak leaves, grape stems, manure – pulled from their property, vintners are able to not only benefit soil health, but also keep as much of its waste on-site as possible.

By Sam Jones

When the winter rains come to Napa Valley, soil erosion is at the top of many viticulturists’ minds. Terracing and other structural changes to the terroir are largely a mitigation method of the past, with many vineyards planting the grassy patches between their rows with mustards, legumes, and grasses as cover crops.

And while the blooming yellows of mustard certainly brighten up Napa’s landscape each year, these widespread plants have important ecological benefits as well.

“It’s all about watershed protection,” said Molly Moran Williams, Industry and Community Relations Director for the Napa Valley Grapegrowers. “Cover crops on hillsides prevent erosion, which, in return, protects our river and watershed.”
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“On top of that, in vineyards all over the valley, cover crops add nutrients back into the soil, increase microbiome diversity, and are used widely as a climate-smart farming practice.”

Each year, growers follow standards mandated by Napa County's Conservation Regulations and Erosion Control Plans (ECP) that prevent erosion and promote water security, protecting public health and preserving natural resources.  The following is a reminder of the annual requirements for Napa County grape growers:

• No earthmoving activities from October 15 to April 1 on slopes greater than 5% (September 1 to April 1 for vineyards in municipal watersheds)
• Winterization for most vineyards including cover cropping and installation of straw waddles by October 15 (September 15 for vineyards in municipal watersheds)

 
The County conducts annual randomized inspections to ensure winterization practices are enforced.  Individual Erosion Control Plans may be subject to other deadlines and extensions based on individual ECPs.
 
Since the 2017 fires, Napa County has allowed property owners to delay the application of straw mulch beyond the winterization deadline by submitting a formal winterization extension request for review and approval.

The Napa County Groundwater Sustainability Agency (GSA) is currently developing a Groundwater Sustainability Plan (GSP) for the Napa Valley subbasin with help from a Groundwater Sustainability Plan Advisory Committee (GSPAC), professional technical consultants, a facilitation team, and Agency staff.  NVG members are represented on this Advisory Committee by NVG Director, Garrett Buckland.
 
The GSPAC is hosting two in-person Groundwater Public Meetings to share information about how the plan will affect the community and hear input, especially with future actions the GSA could take to maintain the health and sustainability of the groundwater subbasin. 
 
They encourage the public to participate in one or both of the scheduled times:
 
First Meeting: Napa Valley College, NVC Little Theater
September 22 | 6pm - 7:30pm
Register Here
 
Second Meeting: Napa  Valley College, Upper Valley Campus
September 29 | 6pm - 7:30pm
Register Here
 
For additional information, visit the GSP website

​Project Summary
The Forrestel lab in the Department of Viticulture & Enology at UC Davis is working on a project to update the Winkler Index to include cultivar-specific growth models and site-specific environmental data to create a tool that growers can use to better understand the most important environmental drivers of berry development and chemistry.  Recognizing that growers across California continue to reference the Winkler Index, these revisions will improve its usefulness as a tool in viticultural decision-making and may provide guidance for long-term planning in the face of climate change.
 
Grower Participation
The initial focus is on Cabernet Sauvignon in different Napa Valley AVAs.  Napa Valley Grapegrowers who are willing to share their weather station data and records related to their Cabernet Sauvignon vineyard sites are invited to participate.

1. Local weather data (hourly preferred)
2. Historical phenological data (e.g. timing of bud break, bloom, veraison, and harvest)
3. Soil depth/characteristics (e.g. from soil pits or other sampling)
4. Irrigation information/schedule
5. Vine information (e.g. age, clone, rootstock, training and trellising)
6. Other relevant vineyard management practices (e.g. pruning, leaf and fruit removal practices, use of shade cloth or misting for heat mitigation, etc.)
7. Ability to collect small samples from each block this season for chemical analysis. Members of the Forrestel Lab are available to help with the compilation and organization of records

• Please note that all of the data that is provided for this project is anonymous, and we will not publish any geolocality data
• At a minimum, they need on-site climate and baseline phenology data to include vineyard blocks in the study

Dr. Patty Skinkis, Oregon State University, and Dr. Markus Keller, Washington State University, along with a multi-institutional research team have launched the High Resolution Vineyard Nutrition Project, which aims to develop methods and tools for vineyard nutrient management. As they start this 4-year project, the first step is to benchmark and understand how grape producers decide to fertilize vineyards and what procedures are being used in vineyard nutrient management.
 
Napa Valley grape growers, consultants, and vineyard management companies are all invited and encouraged to participate in the survey to ensure that Napa Valley is represented. The survey will gather input on what, how, and why nutrient practices are used in vineyards. Learn more about the project.