大会講演
Agroecological Research, Extension, and Education at the University of California, Santa Cruz
2025 年 61 巻 1 号 p. 56-62
詳細
2025 年 61 巻 1 号 p. 56-62
This paper highlights how agroecological research, extension, and education have been conducted at the University of California, Santa Cruz (UCSC) for over four decades. UCSC has one of the world’s oldest formal agroecology programs, known today as the Center for Agroecology. Located near the largest strawberry production area in the US, UCSC’s agroecological research and extension have primarily focused on solving various challenges for organic strawberries using a grower’s participatory approach. Agroecological education has been conducted at the interdisciplinary Department of Environmental Studies, Division of Social Sciences, since 1981. An agroecology major (B.A.) created in 2020 offers lectures, labs, and field quarters for students to learn about ecological concepts of sustainable agricultural systems and develop an understanding of agriculture’s social, political, and economic aspects. The organic campus farm, established in 1971, and organic Chadwick Garden, established in 1967, are managed by Center for Agroecology staff and students and provide the campus and local community with fresh organic produce, hands-on educational opportunities, and fields and facilities for research. Agroecology programs at UCSC continue to evolve to provide opportunities to study, learn, and collaborate in agroecological research, extension, and education for present and future generations to transform entire food systems into more sustainable ones.
The University of California, Santa Cruz (UCSC), established in 1965, is located on the north edge of Monterey Bay on the Central Coast of California, U.S.A. About half of the 800-hectare campus is covered by redwood forest, where ten residential colleges and five academic divisions are dispersed1. More than 19,000 students are enrolled in undergraduate, graduate, and professional degree programs at UCSC.
UCSC’s Center for Agroecology (The Center), one of the world’s oldest formal agroecology programs, was founded by Stephen R. Gliessman2 in 1981. The Center manages the campus farm (10 hectares, established in 1971), the oldest certified organic university farm in the nation, and organic garden (0.8 acres, established in 1967) to provide students, staff, faculty, and local communities with fresh organic produce, hands-on educational opportunities, and fields and infrastructures for research.
I have worked at UCSC as a soil scientist/agroecologist since 1996. Below, I will highlight how agroecological research, extension, and education have been conducted at UCSC for over four decades, focusing on projects I was involved in.
Located near the largest strawberry production area in the US, UCSC’s agroecological research has primarily focused on solving the various production issues in organic strawberries3.
(1) Context: Strawberry production on the California CoastStrawberry production in California is a two-billion-dollar industry that produces about 90% of fresh market strawberries in the US. With its mild summer of the Mediterranean climate in coastal California, large-scale open-field strawberry production (av. 23ha/farm) is distributed along the coast from Santa Cruz County (north) to Ventura County (south). Conventional strawberries are arguably one of the most industrialized pesticide-intensive crops that require pre-plant chemical fumigation to control soilborne pathogens and weeds. Accidental exposure to fumigants has caused hundreds of acute illnesses in agricultural workers and nearby residents since early 2000 (CDPR, 2013). This has led to increasingly stringent fumigant regulations and has made developing non-fumigant alternatives a priority.
(2) Organic strawberry production researchGliessman conducted the very first organic strawberry on-farm trial in California with Jim Cochran, a local organic farmer and president of Swanton Berry Farm in Davenport, CA, from 1987 to 1990. Virtually no one believed organic strawberry production was possible at that time, according to Gliessman. After three years of field trials comparing organic and conventional production side-by-side, they found that organic yield was about 72% of the conventional in the third year. They proved organic strawberry production could be economically viable with some price premiums (Gliessman et al., 1996).
Soilborne disease management is one of the biggest challenges in growing organic strawberries. Verticillium wilt, caused by Verticillium dahliae, is a classic lethal soilborne disease in California strawberries. It is difficult to manage since the pathogen can be hosted by more than 400 plant species and weeds. Further, the pathogen’s microsclerotia can survive more than five years without host crops.
The UCSC’s organic farm experienced an outbreak of Verticillium wilt in strawberries in 2001 and 2002, despite a 7-year rotation. Being a diversified small-scale farm in which over 40 crops are grown annually, it was difficult to avoid V. dahliae host crops such as lettuce, tomatoes, and potatoes during the strawberry break period, resulting in a V. dahliae population build-up in the soil and the outbreak.
Coincidentally, the Dutch plant pathologist Ariena van Bruggen visited the Center’s then-director, Carol Shennan, and observed the outbreak and encouraged us to try a newly developed biological alternative to fumigant practice called “biological soil disinfestation” (Blok et al., 2000). This approach uses fermentation in the soil to suppress soilborne pathogens and some weeds by incorporating a labile carbon source into the soil, saturating the soil with water, quickly covering the soil with plastic mulch, and leaving it for three weeks or more. During the fermentation process, compounds and ions toxic to fungal pathogens are created and the soil microbial community shifts, all working together to suppress fungal pathogens.
We learned later that a practice with the same principle was independently developed in Japan as “reductive soil disinfestation” (Shinmura, 2000). Thus, we learned from both approaches and renamed it “anaerobic soil disinfestation (ASD).”
After a series of trials, we found that ASD can effectively suppress Verticillium wilt in strawberries at our organic farm. In 2007, with funding from the US Department of Agriculture and the California Strawberry Commission, we began optimizing ASD for conventional strawberries as an alternative to fumigants. We conducted dozens of field trials comparing ASD and fumigation across the California coast and demonstrated that ASD could provide comparable fruit yield with fumigants (Shennan et al., 2018). Rice bran from rice fields in Northern California served well as a labile carbon source for ASD, but we also found that rice bran is an excellent slow-release nitrogen fertilizer suited to strawberries.
In 2010, growers began to adopt ASD in commercial fields in California, mainly in organic strawberries. A conservative estimate from rice bran sold for this purpose indicated that rice bran-treated organic strawberry acreage reached 1,000 hectares in California in 2023 (Fig. 1). Many growers use rice bran as pre-plant fertilizer, and the exact ASD-treated acreage is unknown.
Changes in organic strawberry acreages in California with or without applying rice bran. Sources: Total organic strawberry acreage; California Strawberry Commission (CSC, 2024). Rice bran applied organic strawberry field acreage: personal communication, Farm Fuel Inc. and FrontierAg Inc.
ASD and rice bran applications have significantly increased organic strawberry acreage in California since 2010. Over 30 years after the first organic strawberry trial by Gliessman and Cochran, organic strawberry acreage in California reached 2,000 hectares in 2023, representing 13% of the state’s total strawberry acreage, of which nearly half received rice bran (Fig. 1).
The increase in organic strawberry acreage using rice bran in the last decade (2013–2022) translates to a reduction of about 1,871 metric tons of fumigant active ingredients that would have been used in growing conventional strawberries4.
Today, ASD research continues to deal with two other newer and now widespread lethal soilborne diseases in strawberries: Fusarium wilt caused by Fusarium oxysporum f. sp. fragariae and charcoal rot caused by Macrophomina phaseolina. Both pathogens have different sensitivity to ASD than V. dahliae, so fine-tuning ASD is necessary. Additionally, rice bran’s price has increased, and studies identified wheat bran to be a less expensive alternative carbon source for ASD (Daugovish et al., 2023). A new project examining dehydrated food waste as a carbon source for ASD is also underway. Environmental impacts of ASD, such as greenhouse gas emissions, are also being evaluated in California (Prescott et al., 2023).
The number of ASD studies has been increasing in other parts of the US and worldwide. As of 2024, it has been studied in 11 states in the US and nine other countries worldwide for high-value crops such as various vegetables, berries, tree crops, and nurseries.
However, ASD is not a silver bullet, and it must be integrated with other available practices (e.g., crop rotation for annual crops, use of resistant cultivars, grafting, etc.) according to each grower’s goals, needs, and resources. To develop location-specific, non-fumigant-based soil health and soilborne disease management strategies, the integrated soil health management framework consisting of comprehensive soil health diagnostics, a suite of soil health management practices, farmer’s location-specific knowledge, and decision support tools were proposed (Muramoto et al., 2022).
(3) Interdisciplinary study to find barriers to adopt ecological practicesTransitioning from chemical soilborne disease management (e.g., fumigation) to ecological soilborne disease management (e.g., integration of ASD, crop rotation, resistant cultivars, etc.) might not be easy for growers. In reality, 87% of total strawberry fields in California were still conventionally managed using fumigants in 2023. Through semi-structured interviews, we explored the possibilities for agroecological transition within the California strawberry industry (Jiménez-Soto et al., 2024).
We found that agroecological practices such as ASD, crop rotations, and diversification are challenging to implement because “locks-ins” block agroecological transitions and preserve the status quo of industrial agriculture through unequal land access and insecure land tenure, and the high cost of labor and other agricultural inputs. These challenges force farmers to prioritize meeting short-term financial obligations over long-term sustainability goals, leaving little space for knowledge-intensive practices to gain traction against fumigation. Thus, technology-based agroecological transitions must be paired with more transformative changes that address the root causes of environmental decline and facilitate socially sustainable production.
Since the first organic strawberry on-farm trial, UCSC’s agroecology group has been working with local growers for their research. This “participatory” approach has been vital in our problem-solving-oriented research and extension. Participating growers play important roles in research projects by providing feedback on research ideas and plans, implementing field trials, conducting extension activities, and evaluating the project.
Santa Cruz County has many organic growers who graduated from the Center’s Apprenticeship in Ecological Horticulture Program5, which helps us find collaborative organic growers. We also built relationships with conventional growers through local UC Cooperative Extension farm advisors and specialists.
For extension, in addition to standard workshops and field days, we conducted collaborative field trials using the “Mother-Baby” design (Snapp et al., 2002). The Mother trial was a small-scale replicated field trial with many treatments established on the UCSC farm (the entire trial was 0.2 acres with 64 plots). Baby trials were distributed on six different local farms, and only a subset of treatments was tested without replications at each farm on a much larger scale (each trial was 0.4ha with four plots). This participatory field trial, combined with monetary compensation for any yield loss compared to the grower standard budgeted in the project, was valuable in introducing new practices, such as ASD, to small-scale growers who could learn and experience the technique without financial risk6.
Agroecology has been taught at UCSC since 1981 in the Department of Environmental Studies, Division of Social Sciences. The undergraduate agroecology class includes lectures, labs, and often field trials. In 1998, Gliessman published the first edition of his Agroecology textbook (Gliessman, 1998) and an accompanying guide for laboratory activities (Gliessman, 2000). Central to the Dept and Center’s mission is a commitment to educational equity through recruiting and retaining underrepresented students and supporting these students’ voices and visions for shaping agroecology education.
In the first edition of his textbook, Gliessman defined agroecology as “applications of ecological principles for development and management of sustainable agroecosystems.” In the 2nd to 4th editions (Gliessman et al., 2023), the definition was changed, reflecting agroecological science’s evolution. In the new definition, the term “agroecosystems” was replaced with “food systems,” emphasizing critical relationships between producers and eaters and the transformation of the entire food systems beyond production systems. More recently, the Center for Agroecology (Center for Agroecology, 2024) defined agroecology as, “the integrative study of the entire food system, encompassing ecological, economic and social dimensions. We acknowledge that to create ecologically sound, economically viable, and socially just food systems, agroecology must integrate science and research, technology and practices, indigenous knowledge, and movements for social change. We embrace agroecology as a transdisciplinary, participatory, action-oriented, and politically-engaged transformation of the food system.”
In 2020, an agroecology major (B.A.) was created in the Department of Environmental Studies (2022). Reflecting the newer definition of “agroecology,” the major was designed to help students learn about ecological concepts that can be applied to developing sustainable agricultural systems and build their understanding of agriculture’s social, political, and economic aspects. Students also engage in hands-on experiences and obtain research, fieldwork, production, and communication skills to achieve multiple sustainability goals in complex, social-ecological food systems.
The first Agroecology Field Quarter was offered in the summer of 2024. This seven-week residential and traveling course accommodates up to 20 students from UC campuses and beyond. Three classes and a lab are included. Throughout the entire program, emphasis is placed on field study, featuring hands-on experiential learning activities on the land. Additionally, students engage in visits to academics, farmers, and community-based organizations at the forefront of agroecology research, extension, farming operations, and community organizing.
(2) Basic needs supportA survey found that more than half of UCSC’s residential students are food insecure due to the extremely high living costs in Santa Cruz. To support educational equity and students, the Center’s Basic Needs team serves free organic meals made from freshly harvested vegetables from the campus farm at the Center-run, student-staffed kitchen and café (Basic Needs Team, 2024). They also provide value-added items integrating organic production, harvesting, and preparation alongside cultural foodways and diverse recipes from the Pop-Up and non-transactional Redwood Market to the Coffee Shop to special events with our Ethnic Resource Centers. About half of the produce grown and harvested by students at the campus farm and garden is consumed by students. Growing, harvesting, cooking, and eating fresh produce on campus provides students with a powerful educational experience on our food systems.
Since the 1980s, the UCSC agroecology group has been developing sustainable farming practices and systems to increase the tools in organic growers’ toolboxes and to prevent pests and diseases from occurring. However, we found that the success of agroecological transitions hinges on weaving individual technologies into a broader framework that addresses the structural challenges facing growers, transforming the social and political relationships inherent in industrial agriculture.
Agroecology programs at the Department of Environmental Studies and the Center for Agroecology, both in UCSC’s Division of Social Sciences, continue to evolve to provide opportunities to study, learn, and collaborate in agroecological research, extension, and education for present and future generations to transform entire food systems into more sustainable ones that are ecologically sound, economically feasible, and socially just.
Emeritus professors Stephen R. Gliessman and Carol Shennan have given me invaluable guidance, support, and inspiration for many years at UCSC, and I am incredibly grateful. I also thank Erin Foley, Tim Galarneau, Ann Lindsey, and Damian Parr for their valuable comments on a previous version of this manuscript.
where FR=the amount of fumigants reduced from 2013 to 2022 by rice bran applications (metric tons), RA=rice bran applied acreage for strawberries in each year (Fig 1), FUA=the amounts of total fumigant active ingredients applied on strawberries in each year (data from the Department of Pesticide Regulation’s Pesticide Use Reporting, CDPR (2024)), and CSA=the conventional strawberry acreage in each year (data from California Strawberry Commission (2024)). Conventional strawberry production always uses fumigant(s).
