Building on Farmer Experience to Increase Cover Crops Adoption in Orchards and Vineyards

Final report for RGR20-006

Project Type: Local Ed & Demo (formerly RGR)
Funds awarded in 2020: $74,594.00
Projected End Date: 04/30/2023
Host Institution Award ID: G158-21-W7906
Grant Recipients: University of California Sustainable Agriculture Research & Education Program; Community Alliance with Family Farmers (CAFF); Napa County Resource Conservation District; Capay Valley Regeneration Project; Cooperative Extension - Capitol Corrridor, Kern, Mendocino, and Napa Counties
Region: Western
State: California
Principal Investigator:
Lucas Patzek
Napa County Resource Conservation District
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Project Information


Cover crops provide important agroecosystem and farm resilience benefits. However, many growers in California either do not use them at all, plant them in strips too narrow, or terminate them too early (due to perceived risks) to gain full benefits, even in perennial systems that appear ideally suited for cover cropping between tree and vine rows. Successful implementation typically involves a steep, multi-year learning curve that can easily be derailed by one bad experience, as evidenced by a recent WSARE-funded almond grower survey that found that many growers had tried cover crops at least once but were not currently using them. While many publications and websites provide general information about cover crop species, they typically lack key details about management approaches required for success in specific climates, crop and soil types, enterprise management strategies, and economic circumstances.

This project will address these shortcomings by creating region and crop-specific information platforms based on experienced farmers’ best management practices for specific contexts in orchard and vineyard systems in northern California. Specifically, it will create an online searchable database of best management practices as implemented in the southern Sacramento Valley and North Coast regions. Curated by UC SAREP, the database will provide for user entry, allowing farmers to add new information to keep the database relevant and adaptive over time. We will also organize two field tours of successful cover cropping operations.

This project will also 1) refine and pilot test a new cover crop species selection tool recently developed by Cooperative Extension, for California conditions, and 2) link the selection tool to UC SAREP’s Cover Crops Database, updated with information from at least two previous WSARE projects. These new resources will be publicized to growers throughout the project regions through existing networks, field days, newsletters, and social media of partners.

Project Objectives:
  1. Increase the circulation among farmers and agricultural professionals of regionally-relevant, grower-generated information on best management practices for cover cropping in orchard and vineyard systems in the southern Sacramento Valley/Delta region, and North Coast viticulture region.
  2. Increase the confidence, skill-level, and sophistication of orchard and vineyard managers in implementing cover crops in these regions.
  3. Increase the accessibility of accurate, science-based information about cover crop species relevant to these regions and production systems.
  4. Increase understanding among growers and agricultural professionals of the characteristics of relevant cover crops species and how they can meet orchard and vineyard growers’ farm management goals.

This project will utilize findings from Creze et al. GW18-142, Cover Crop Systems for Almond Orchards: Exploring Benefits and Tradeoffs to Inform Management and Westover et al. OW14-032, Selecting and Managing Vineyard Cover Crops to Reduce Consumption of Net Basin Water.

A 2015 sustainability assessment by the Almond Board of California indicated that only 5.6% of almond growers had planted winter cover crops (ABC 2015). Creze et al.’s survey indicated that, while all respondents recognized potential benefits from cover cropping, operational difficulties, such as stand establishment, were cited as barriers (more than agronomic or economic challenges). Additionally, multiple project partners who work with orchard growers in the region indicate that perceptions about increased frost risk, water use, and excess plant residue at harvest time prevent many growers from trying cover crops. Creze et al.’s preliminary field data, however, suggest that these issues do not occur as often as growers may think and that management options exist to limit potential tradeoffs.

In the North Coast viticulture region, an unpublished, three-county survey by Resource Conservation Districts indicates that over 20% of growers are concerned with gopher problems in cover crops – another operational challenge – and 16% percent worry about water stress in vines from cover crop competition, at a time when water use reductions may soon be mandated under California’s Sustainable Groundwater Management Act. As a result, many plant cover crops in narrow strips, leaving nearly 50% of the soil exposed, or terminate early. Westover et al. (OW14-032) found that different species and termination dates did not significantly affect soil moisture levels in the Central Coast region, which is generally drier than the North Coast. Dissemination of this information will help North Coast growers make cover crop selection and management decisions based on other priorities than water use, such as maintenance of beneficial habitat to control critical vineyard disease vectors.

The above orchard and vineyard surveys both indicate a need for communication of findings on commonly perceived risks, and regionally-specific operational best management practices and species selection tools. However, the pace of field-based research on cover crops for different bioregions across the state has been slow, with a literature review by Creze et al. showing few scientific studies relevant to perennial crops in California in recent decades. Meanwhile, we know of a number of innovative growers in both regions who have conducted their own experiments with cover crops, and yet the reasons for their successes – as well as the lessons to be gathered from failures – remain largely undocumented and unshared. 

Additional SARE research: Hoddle et al. (SW07-022 – Using Nectar Cover Cropping in Vineyards for Sustainable Pest Management) found that vetch and buckwheat increased longevity and fecundity of mealybug and glassy winged sharpshooter parasitoids in laboratory trials. This information will be added to technical information in our cover crops selection tools. Field trials from this study will not be applicable to our North Coast and Sacramento Valley regions due to significantly hotter and drier conditions in the southern California site. 


Click linked name(s) to expand/collapse or show everyone's info
  • Mica Bennett (Educator)
  • Monica Cooper (Educator)
  • Miguel Garcia (Educator)
  • Amelie Gaudin, Sonj (Researcher)
  • Barbara Gemmill-Herren - Producer (Educator)
  • Katherine Jarvis-Shean (Educator)
  • Glenn McGourty (Educator and Researcher)
  • Shulamit Shroder (Educator)
  • Ruby Stahel (Educator)
  • Sara Tiffany (Educator)
  • Houston Wilson (Educator)
  • Mohammad Yaghmour (Educator)

Education & Outreach Initiatives

Farmer-to-farmer outreach on cover cropping practices

1. Increase the circulation among farmers and agricultural professionals of regionally-relevant, grower-generated
information on best management practices for cover cropping in orchard and vineyard systems
in the southern Sacramento Valley/Delta region, and North Coast viticulture region.
2. Increase the confidence, skill-level, and sophistication of orchard and vineyard managers in implementing
cover crops in these regions.


We designed a searchable database hosted and curated by UC SAREP, to capture best management practices for cover crops in orchards and vineyards ( The database, based on extended interviews with 42 different growers, provides access to 51 individual farm/orchard block entries, with detailed information about soil types, cover crops and primary crop species, cover crops management practices, strategies for addressing common challenges relating to establishment and termination of the cover crop, strategies for interfacing with tree or vine crops, and information about why and how the grower first got started on cover cropping. The database provides scope for addressing the particular goals and challenges described by respondents to Creze and Gaudin’s almond grower survey (GW18-142). Approximately half of the entries are for winegrape production in the North Coast region, and half are for nut and tree fruit orchards and grape production in the Sacramento Valley region. Farms are located across the following counties: Napa, Sonoma, Lake, Colusa, Sacramento, Yolo, and Solano.

In February and March, 2023, we hosted three cover crops farm tours – one at a Napa vineyard and two tours visiting a total of five farms in Sacramento Valley orchards and vineyards. These 2-4-hour tours showcased on-the-ground practices of experienced growers with different species and crops. In addition to the growers themselves speaking extensively about their practices, additional guest speakers included Hope Zabronsky and Kosana Suvocarev from UC Cooperative Extension (researching frost risk and water use of cover crops), Rory Crowley from Project Apis m. (technical service provider and cover crop funding assistance) and Hanna Kahl from Community Alliance with Family Farmers (conducting applied pest management trials in cover cropped orchards). We have disseminated information about the expert growers database to growers at the farm tours, and have also spread the information to both growers and extension professional via our UC SAREP quarterly newsletter and associated social media, at a statewide cover crops experts convening, at a statewide UC Agriculture and Natural Resources conference, and by presenting in a session of a statewide conference sponsored by the California Association of Resource Conservation Districts. The database and broader cover crops website (see below) will continue to be disseminated to the UC Agriculture and Natural Resources workgroups and program teams, including the Pomology Program Team, and the Agroecology and Organic Farming Systems Workgroup, as well as via the North Coast Soil Health Hub, and the newly established Western Cover Crops Council. Articles will be included in upcoming late summer-early fall newsletters, as the next winter cover crop planting season approaches.


Outcomes and impacts:

Post-tour evaluations provided some indications of learning outcomes. Of the 42 people who responded to the question, 40 (95%) indicated that their knowledge about growing cover crops in orchards and vineyards increased as a result of the tours, and 41 (98%) reported an increase in their awareness of the possibilities of cover cropping in orchards and vineyards. In addition, 94% of 36 respondents indicated that they either already do or will probably utilize the expert cover crop grower database in the next year.

Information about the database was disseminated during the 2022-23 winter cover cropping season, and it has received almost 3,500 page views by this writing in June, 2023. It will take until at least the next cover cropping season or two to see whether longer term, hoped-for outcomes, such as increases in grower adoption or overall extent of use of cover crops in orchards and vineyards, are realized. However, of the 31 individuals who responded to this question in cover crop tour evaluation surveys, 12 (39%) indicated that they will "probably begin growing a cover crop in the next year". Their reported acreage for potential new cover crop planting is roughly estimated at 1290 acres.


Enhance accessibility of cover crops species information tools

1. Increase the accessibility of accurate, science-based information about cover crop species relevant to these regions and production systems.
2. Increase understanding among growers and agricultural professionals of the characteristics of relevant cover crops species and how they can meet orchard and vineyard growers’ farm management goals.


The original plan for this project to update, expand, and coordinate the technical content of an early prototype model of a California-oriented, Excel-based cover crop species selection tool became infeasible to complete. The comprehensive review of the tool's technical content by 16 university and non-university cover crops experts revealed some important disagreements on specific characteristics of different cover crop species under different regional growing conditions. Our initial attempts to engage with and reconcile these differences in expert opinions were unsuccessful and revealed that vetting these items across the large number of growing regions of California, with a wide variation in climate and soil conditions, would not be possible without an extended and more systematized group review and discussion process. Around this time, USDA decided to award the Western Cover Crops Council a substantial grant and staff support to conduct an extended, multi-stakeholder review process to create a western cover crops species selection tool similar to the tools that have already been created for other regions of the U.S. With those resources and timeline exceeding what was available in this project by many-fold, we made the decision to abandon any further plans to work on this prototype tool. 

The user-interface for the already existing UC SAREP Cover Crops Database was modernized and improved to make key information categories for each species searchable by users of this database.

Remaining project resources were re-directed toward building up a more comprehensive "California Cover Crops Resources" website (, and creating original content for this website. This content comprises 8 narrative summaries of grower challenges and perspectives on cover cropping ( These summaries delve deeper into grower perspectives on specific topics than the shorter database entries, and supplement growers' experiences with summaries of recent scientific results pertinent to these topics. Subjects covered include the effects of cover crops on pests such as navel orangeworm and nematodes, soil water management and cover crops, and grazing cover crops. Those summaries that report scientific results have been peer-reviewed. One summary on frost risk with cover crops is still being amended with new data from a very recent study, and will be posted as soon as it is completed and reviewed.

In addition to this original content, this website consolidates many pieces of information pertinent to cover cropping that had previously been scattered across several different websites. UC SAREP staff will continue to solicit more cover crops content from colleagues across the state, and will continue to post new resources from reputable sources, including the Western Cover Crops Council's new species selection tool once that is completed.

Outcomes and impacts:

The new website has received over 5,700 views since its inception in late 2022. We cannot assess action outcomes but expect that it will help growers of orchard and vineyard crops in these regions to increase their knowledge of cover crops and increase their confidence in trying cover cropping and working through common challenges.

Educational & Outreach Activities

2 Consultations
10 Curricula, factsheets or educational tools
1 Published press articles, newsletters
3 Tours
4 Webinars / talks / presentations

Participation Summary:

36 Extension
27 Researchers
43 Nonprofit
2 Agency
26 Ag service providers (other or unspecified)
305 Farmers/ranchers
695 Others
Education/outreach description:

In addition to the three cover cropping farm tours described above, we carried out the following activities:

1. Brief informative presentations and/or live demonstrations of the Expert Cover Crop Grower Database at the following:

  • California Cover Crops Experts Convening meeting, Oct 18, 2022, Merced, CA - approximately 50 total attendees, primarily researchers, nonprofit, and extension
  • California Climate and Agriculture Network Summit - Nov 14, 2022, Davis, CA - at least 7 people viewed website demonstration and/or project fliers during poster session, and likely more saw project fliers
  • Cover Crops, Hedgerows, and Strategies for Improved Orchard Management on-farm field day, hosted by Community Alliance with Family Farmers, Colusa County, CA - at least 9 nonprofit staff and/or farmers heard presentation about the database

2. Extended webinar presentation and demonstration of Expert Grower Database and new website:

  • California Association of Resource Conservation Districts online annual conference, March 29, 2023: at least 30 people from nonprofits or unspecified attended the presentation

3. Poster presentation about the database and website:

  • Univ. of California Agriculture and Natural Resources Statewide Conference, April, 2023: at least 25 or more people viewed poster or project flier (primarily an extension audience)

4. Newsletter articles:

  • UC SAREP quarterly newsletter: announcement of new Expert Cover Crop Grower Database: circulated to at least 965 subscribers, including 270 farmers/ranchers



Learning Outcomes

40 Service providers reported changes in knowledge, attitudes, skills and/or awareness as a result of project outreach
14 Ag professionals intend to use knowledge, attitudes, skills and/or awareness learned

Project Outcomes

1 New working collaboration
Project outcomes:

In summary, hundreds of farmers and agricultural professionals have learned about successful species and management strategies being used in orchards and vineyards in northern California, and several reported intending to plant cover crops in the next year. Please see above for detailed learning and intended action outcomes described by project objectives.


Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.