Progress report for RGR20-006
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.
- 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.
- Increase the confidence, skill-level, and sophistication of orchard and vineyard managers in implementing cover crops in these regions.
- Increase the accessibility of accurate, science-based information about cover crop species relevant to these regions and production systems.
- 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.
- - Producer (Educator)
- (Educator and Researcher)
Education & Outreach Initiatives
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 will design a searchable database infrastructure to be hosted and curated by UC SAREP, to capture best management practices for cover crops in orchards and vineyards. The database will provide access to individual farmer cases 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 any other important variables to be identified by the advisory committee. The database design will provide scope for addressing the particular goals and challenges described by respondents to Creze and Gaudin’s almond grower survey (GW18-142).
We will host two cover crops farm tours – one in North Coast vineyards and one in Sacramento Valley orchards - to showcase on-the-ground practices of experienced growers with different species, during the winter/spring cover crops season. We will disseminate information about the farmer management practices database and species selection tools to growers at partners’ existing field days and workshops, and via their websites, newsletters, and social media, and to the North Coast Soil Health Hub and newly established Western Cover Crops Council.
January 2022 Update: The project team has completed 44 detailed interviews with growers who are experienced with cover crop usage - 22 in the Sacramento Valley area (orchards and vineyards), and 22 in the North Coast area (vineyards). The information generated is being standardized and the design of the searchable database is still underway.
This initiative has not yet been started. We expect that it will help growers of orchard and vineyard crops in these regions to increase their confidence levels around cover cropping and will help them to avoid common pitfalls that often discourage growers from continuing with cover crops in subsequent years.
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.
We will update, expand, and coordinate the technical content of two cover crop species information resources: 1) an early model of a California-oriented Excel-based species selection tool, modeled after the selection tool of the Southern Cover Crops Council, and 2) the UC SAREP Cover Crops Database, https://ucanr.edu/sites/asi/db/covercrops.cfm, a highly accessed resource for 43 species that has not been updated for over a decade. The project team will focus on a subset of species most suitable for orchards and vineyards in the project region, ensuring that both resources contain up-to-date information, and linking them such that users obtaining species lists as output from the Excel-based tool can access the more qualitative descriptions in the UC SAREP database for more information. We will incorporate region-specific information obtained in the farmer interviews for the cover crop practices database (described above). We will advertise updated resources at a number of grower-oriented events and newsletters hosted regularly by project collaborators, and through other entities such as the Western Cover Crops Council.
January 2022 Update: The draft, Excel-based cover crops species selection tool that had been developed by a Cooperative Extension office, was, under this current project, comprehensively reviewed by 16 UC and external cover cropping experts familiar with many different regions of California. Our project team took specific content input from this group to improve the characterizations of different species in the tool, and we also re-vamped the interface to be more user-friendly. This revised tool is currently undergoing a final review for accuracy by this group of 16 experts. The user-interface of the UC SAREP Cover Crops Database was also modernized and improved to make key information categories for each species searchable by users of the database.
This initiative has not yet been started. We expect that it will help growers of orchard and vineyard crops in these regions to increase their science-based knowledge of cover crop species.
Educational & Outreach Activities
We are still in the planning stages and no outcomes have been achieved to date.