UC Food Blog

Organic strawberry yields boosted by technique refined through UCCE research

There is a stark difference in plant vigor between an ASD-treated plot (left) and a standard untreated plot in an organic field infected with charcoal rot. Photo by Joji Muramoto

Anaerobic soil disinfestation helps suppress weeds, disease without fumigants

Troubled by puny plants, low yields and persistent mite problems, third-generation Southern California strawberry grower Glen Hasegawa was ready to give up on his transition from conventional to organic 12 years ago.

“I've always liked a challenge – but it turned out to be more of a challenge than I thought it would be!” he said.

But then, with the help of scientists including Oleg Daugovish, UC Cooperative Extension strawberry and vegetable crop advisor in Ventura County, Hasegawa tried a technique called anaerobic soil disinfestation (ASD). When applied correctly, the multi-step ASD process creates a soil environment that suppresses pathogens and weeds and makes for healthier, more robust crop growth.

“Back in the day, it was really hard to get the plant growing vigorously in organic,” said Hasegawa, owner of Faria Farms in Oxnard. “So we started using the ASD and then you could definitely see that the plant had more vigor and you could grow a bigger, better plant using it.”

Seeing that he could produce yields “in the neighborhood” of those grown in conventional strawberry fields fumigated with synthetic fumigants, Hasegawa was able to expand his original 10 acres of organic strawberries to 50 acres.

“I guess you could say I'm kind of a convert,” he said, noting that he now applies ASD to all his acreage each year in late spring.

Joji Muramoto, UC Cooperative Extension specialist in organic production based at UC Santa Cruz, has been experimenting with ASD since it was first brought to the U.S. from the Netherlands and Japan in the early 2000s. Carol Shennan, a professor in the Department of Environmental Studies at UCSC, and Muramoto were among the first to try the technique in California. They found that ASD successfully controlled an outbreak of Verticillium wilt – caused by the pathogen Verticillium dahliae – at UCSC's small organic farm in 2002.

Since then, Shennan, Muramoto, Daugovish and their colleagues have seen encouraging results at 10 trial sites across the state.

“We demonstrated that ASD can provide comparable yields with fumigants, in side-by-side replicated trials,” Muramoto said.

The strawberry plants in the ASD-treated plot (left) are more robust than those growing in untreated soil. A plastic mulch (typically opaque is used by growers, but clear was used here for research purposes) is crucial as part of the ASD process to improve plant productivity and control weeds. Photo by Oleg Daugovish

ASD promotes host of beneficial changes to soil ecosystem

ASD comprises three basic steps: incorporating a carbon source that is easily digestible by microbes in the soil (traditionally, rice bran has been used), further encouraging fermentation by covering the soil with plastic to limit oxygen supply, and finally adding water through drip irrigation to initiate the “anaerobic” decomposition of the carbon source and maintain the three-week “cooking” process.

The resulting cascade of chemical, microbiological and physical changes to the soil creates an ecosystem that is both conducive to strawberry growth – and inhospitable to pathogens and weeds.

“It's not like a pesticide where you have a mode of action, and thus resulting in ‘A' and ‘B' for you,” Daugovish explained. “There's a sort of cocktail of events that happens in the soil; they all happen interconnectedly.”

Compared to similar fields that did not undergo the process, ASD-applied organic strawberry fields across California have seen yields increase by 60% to 70% – and even doubling in some cases, according to Daugovish.

The UCCE advisor also shared the story of a longtime grower in Ventura County, who came to him with fields in “miserable” condition; they were plagued by one of the world's worst weeds, yellow nutsedge, and infected with charcoal rot, a disease caused by the fungus Macrophomina phaseolina. But after applying rice bran and following the ASD recipe, the grower saw phenomenal results.

“The only complaint he said to me was, ‘Now I have too many berries – we have to have more pickers to pick the berries!'” Daugovish recalled.

Via researchers' meetings, online resources, on-farm demonstration trials and word of mouth from peers, use of ASD by California strawberry growers has grown significantly during the past two decades. Tracking the purchase of rice bran, Muramoto estimated that about 2,500 acres were treated by the ASD-related practices in 2023 – covering roughly half of the 5,200 total acres of organic strawberries in California.

Muramoto directly links the growth of California organic strawberry production – which now comprises about 13% of total strawberry acreage in the state – with the increasing adoption of ASD.

“If you remove the acreage with the applied rice bran over the last 10 years or so, organic strawberry acreage is just flat,” he said.

Applying rice bran provides the easily digestible carbon source that soil microbes feed on. Once covered by plastic mulch, anaerobic conditions develop and microorganisms that prefer such an environment thrive, while pathogenic organisms and germinating weeds are suppressed. Before planting, holes are cut in the plastic to let oxygen back into the soil and encourage the growth of the strawberry plants. Photo by Oleg Daugovish

Within the last decade, acreage of organic strawberries with ASD-related practices increased by 1,640 acres, which is a boon for air quality, human health and long-term soil vitality. According to Muramoto's calculations, that increase in organic acreage translates to a reduction of about 465,000 pounds of fumigant active ingredients that would have been used in growing conventional strawberries.

“There are hundreds of reports of acute illnesses related to fumigation in the record, so it's very important to find alternatives to fumigants,” said Muramoto, citing California Department of Pesticide Regulation documents.

Research continues to make ASD more economical, effective

The popularity of ASD has come at a price, however, for organic strawberry growers.

“There's more organic out there, and I think most of the organic guys are using it, so there's more demand on the rice bran; the price has been steadily going up every year, like everything else,” said Hasegawa, adding that he has been trying to decrease the amount of carbon while maintaining ASD's efficacy.

On top of greater demand from other growers and from beef cattle and dairy producers (who use rice bran as feed), the price also has increased due to higher costs in transporting the material across the state from the Sacramento Valley. So Daugovish and his colleagues – including Peter Henry, a U.S. Department of Agriculture plant pathologist – have been searching for a cheaper alternative.

“We all want an inexpensive, locally available, reliable, easy to use and functional carbon source, which sounds like a big wish list,” Daugovish said.

Carbon sources such as bark, wood chips, or compost are ineffective, as the crucial ASD microorganisms are choosy about their food.

In a field of 'Victor' strawberries, researchers saw a 41% increase in yield using ASD with midds, in comparison to untreated soil. Photo by Oleg Daugovish

“Microbes are just like cows; you can't feed them straight wood; they get pretty angry,” Daugovish explained. “And if you feed them something with too much nitrogen, they can't digest it – they get the runs. Microbes are the same way – you have to have the right proportion of stuff so they feel comfortable doing what they're doing.”

In search of an ideal replacement, researchers tried and ruled out grass clippings, onion waste, glycerin and coffee grounds. Finally, they pivoted to a material with properties very similar to rice bran: wheat bran, in the form of wheat middlings (also called midds, a byproduct of flour milling) and dried distillers' grain (DDG, a byproduct of ethanol extraction).

After field experiments in Santa Paula, the UC and USDA researchers found that midds and DDG were just as effective at controlling soilborne pathogens and weeds as rice brain – but at 25% to 30% less cost. Their results were published last year in the journal Agronomy.

“Not surprisingly, the wheat bran has worked almost exactly the same as rice bran,” Daugovish said.

He and Muramoto are now conducting trials with wheat bran at commercial fields, and the initial results are promising. Daugovish said the grower at one site in Ventura County has seen a 90% reduction in Macrophomina phaseolina, the causal pathogen of charcoal rot, in the soil – and an 80% to 90% drop in yellow nutsedge germination. They are waiting for final yield numbers after the coming summer.

While ASD has been beneficial to organic productivity and soil health, both Daugovish and Muramoto acknowledged specific limitations in suppressing the “big three” strawberry diseases: Verticillium wilt, Fusarium wilt and charcoal rot. In coastal areas with cooler soil temperatures, for example, ASD can actually exacerbate the latter two diseases, as the fungal pathogens feed on the rice bran.

“We know it works at warmer temperatures, but, practically, it's hard to do in coastal California,” Muramoto said. “It would be nice if we can find a way to suppress Fusarium wilt at a lower temperature, but we don't have it right now.”

That's why researchers emphasize that ASD is not a “silver bullet.” It's just one tool in the organic toolbox, which includes careful crop rotation, disease-resistant strawberry varieties and better diagnostic tests that help growers pinpoint outbreaks and make the application of various methods more targeted and more efficient.

And scientists will continue to optimize ASD to make it more effective and economical for growers in the different strawberry regions of California – from the Central Coast to the Oxnard Plain.

“We know it can work really well; it's just finding the most sustainable way to do this in our region,” Daugovish said. “We've got to just have an open mind and keep trying.”

REC System Director Haver encourages systemic approach to agriculture

Darren Haver (center) and fellow roundtable participants raise their hands when asked the question, "how many of you work in agriculture?" All photos by Saoimanu Sope.

Agriculture generates $59 billion and employs nearly 400,000 individuals in California. The industry, however, is often threatened by challenges like climate change, land conversion and water scarcity. Motivated to act, Sustain Southern California – an organization associated with UC Irvine Beall Applied Innovation – hosted a roundtable discussion on Feb. 20 featuring subject matter experts including Darren Haver, director of UC Agriculture and Natural Resources' Research and Extension Center System.

During his keynote address, Jose Arriaga, Orange County Agricultural Commissioner, defined sustainability as food and fiber production that does not compromise the ability for future generations to meet their needs. In doing so, he acknowledged the benefit of discussing such timely topics with key players, especially for places where agriculture is not as prevalent as it used to be. 

“Many people don't think of Orange County as a place for agriculture. It's probably because less land is being reserved for agriculture, not like back in the day. And that worries me,” said Arriaga. 

Jose Arriaga (left) and Haver (right) during the Sustain SoCal event hosted at the UC Irvine Beall Applied Innovation Center.

The first roundtable discussion centered on sustainable agriculture, with Haver participating alongside other industry leaders based in Southern California, including A.G. Kawamura of Orange County Produce, Steve Brazeel of Sunterra Produce and Elevated Foods, Anthony Curci of Buttonwood Ranch and Parker Cohn from Performance Resource Management.

In discussing today's generation, Haver said that he has seen a shift over the last few decades away from yield alone, which used to be the most important aspect of production in agriculture. Today, much more attention is dedicated to sustainability – a change that Haver attributes to the younger generation of researchers and plant scientists working in agriculture.

There has also been an emphasis on sustaining the environment while maintaining economic progress. Haver recognized these important elements, but highlighted the social impact of sustainability, too.

“I don't have all the answers, but I do believe that addressing the environmental, economic and social aspects of agriculture is important. I also think that these factors should be addressed systemically rather than in silos,” said Haver.

Southern California agricultural producers, in particular, are responsible for $7.8 billion in gross receipts and nearly 100,000 jobs directly related to agriculture. In Orange County alone, where Haver is based at the South Coast Research and Extension Center, agriculture makes up $86 million of total economic output, with nurseries leading as a top commodity followed by fruit trees, vegetable production and livestock and apiary.

Climate-smart crop production workshops March 5-7 in Ventura, Salinas and Tulare

Workshops will cover the latest research and advances in managing risks to agricultural production that can result from climate change and climate variability.

Growers invited to learn how to manage risks to fruit, nut, vegetable production

UC Cooperative Extension is offering workshops in Ventura, Salinas and Tulare to help growers adapt their fruit, nut and vegetable production practices to variable climate conditions.

"Growers, farm and ranch managers, and technical assistance providers can learn about the latest research and advances in managing risks to agricultural production that can result from climate change and climate variability,” said Daniele Zaccaria, associate professor in agricultural water management for Cooperative Extension at UC Davis.

Tapan Pathak, UCCE specialist at UC Merced, will speak about climate change trends, potential impacts on agricultural production and decision support tools. Zaccaria and local experts will discuss cover cropping, pests and other issues.

During a roundtable session, participants will discuss their own production challenges resulting from climate change and variability.

“Participants will also learn about tools available to aid manage climate change and climate variability risks," Zaccaria said. 

The Climate-Smart Agricultural Production Practices workshops will be held in three locations: 

Ventura: Vegetable and Berry Production

March 5 (8 a.m.–1:30 p.m.)
669 County Square Dr., Suite 100

Speakers include UCCE advisors Andre Biscaro, Ben Faber and Mark Battany, and other scientists and experts from Ventura County Resource Conservation District and Land IQ. Register at https://bit.ly/VenturaCrops.

Salinas: Vegetable, Berry and Grapevine Production

March 6 (8 a.m. –2 p.m.)
1432 Abbott St.

Speakers include Daniel Hasegawa and Eric Brennan of USDA-ARS and UCCE advisors Larry Bettiga, Michael Cahn and Mark Bolda. Register at https://bit.ly/SalinasCrops.

Tulare: Fruit and Nut Production

March 7 (8 a.m.–2 p.m.)
4500 South Laspina St.

Speakers include UCCE advisors Jhalendra Rijal, Mark Battany, Mohammad Yaghmour, Sandipa Gautam, Brent Holtz and other scientists and experts from USDA-NRCS, Almond Board of California; California Pistachio Research Board and Land IQ. Register at https://bit.ly/TulareCrops.

Workshops are free and include coffee breaks, lunch, workshop materials along with the presentations. Registration is required. 

These workshops are supported by grants from the California Department of Food and Agriculture and USDA's National Institute of Food and Agriculture.

‘Super Carbolicious’ 4-H Food Fiesta challenges young chefs

Sadie, 4-H member of Orange County, begins her presentation in front of two judges. All photos by Saoimanu Sope.

Inside a quiet classroom, Sadie, a 4-H member in Orange County, stands in front of two judges with an insulated cooler bag in hand. From it she pulls out plates, utensils and napkins and sets them down on the table. She unzips the bottom compartment and carefully reaches for a cast iron platter with golden fluffy pancakes piled on top.

“Would you like syrup with your pancakes? I highly recommend it,” said Sadie, an eighth grader who is participating in the annual 4-H Food Fiesta for a second time.

4-H, a youth development program supported by the University of California Agriculture and Natural Resources and administered through local UC Cooperative Extension offices, promotes hands-on experiential learning for all youth.

Rita Jakel, 4-H program coordinator for Orange County, described the Food Fiesta event – intended for ages 5 to 18 – as an opportunity to practice and showcase public speaking skills through a fun, food-related competition.

Youth present their creations before a panel of evaluators, who ask them to describe how they prepared the dish and why, and how they managed challenges throughout the process. The interaction between youth and adult leaders provides a unique opportunity for youth to practice career readiness skills such as job interviews and public speaking.

Kaitlin, 4-H member and first-time participant in the annual Food Fiesta.

This year's theme was “Super Carbolicious” and 4-H participants were encouraged to make their favorite dishes using ingredients like pasta, potatoes and bread. Carbohydrates are often perceived as unhealthy, which is not a helpful mindset to have when teaching youth about nutrition. Carbohydrates provide the body with glucose, which is converted into energy that people need to function throughout the day.

Some of the dishes that were presented during the Food Fiesta included chocolate chip banana bread, cheesy baked potatoes, cookies and Nutella-stuffed crepes. 4-H member Kaitlin had only ever attended the Food Fiesta to cheer on a friend. This year, she decided to participate and presented pumpkin macaroni and cheese as her entry.

“Pumpkin mac and cheese is better than the regular one because there's a lot more flavor and you have to use two cheeses: cheddar and parmesan,” explained Kaitlin, a seventh grader. When asked what motivated her to participate instead of a being a bystander this time around, Kaitlin said that she wanted to work on her presentation skills. 

“Usually, I'm a bit shy and I don't like to share that much. The Food Fiesta helped me practice speaking up more so that I can accomplish my goals,” Kaitlin said.  

Sadie, who loves public speaking, admits that it wasn't always a strength of hers. “There was a time when I hated public speaking. But when I joined 4-H's cake decorating, poultry and food fiesta events, I got more comfortable with public speaking,” she said. “Now, I like going to events and showing off. I get to show off turkeys, my cakes and, today, I presented homemade pancakes.”

Sadie presents her Food Fiesta entry of homemade pancakes.

Helping to keep the day's festivities running smoothly were two 4-H state ambassadors: Michaela and Laurelyn, two high school seniors. Both have been involved in 4-H for over nine years, with Laurelyn being a third-generation 4-H member. “My grandmother grew up in a 4-H club in Orange County. She still raises breeding lambs for 4-H members to this day,” said Laurelyn, whose mother was a 4-H member in San Joaquin County.

As state ambassadors, they are responsible for creating and presenting workshops during state, national and regional events. “We also engage the public via social media, specifically TikTok and Instagram (@4horangeco),” said Michaela, who is in her second year as an ambassador.

During the Food Fiesta, Michaela and Laurelyn made themselves available to answer questions from participants and their families. Both ambassadors agreed that seeing parents involved in 4-H should not come as a surprise. “Being in 4-H is a family effort. This isn't an extra-curricular where you just drop your kids off and leave,” said Michaela.

Laurelyn shared that the biggest misconception others have about 4-H is that they think it's about introducing youth to agriculture or livestock. There's a civic engagement and leadership component to it, too. “If parents knew about all the ways 4-H can benefit their kids, I think more people would want to join us,” she said. “And they're finding fun ways to help us learn life skills, like this Food Fiesta.” 

Michaela and Laurelyn, 4-H State Ambassadors and long-time 4-H members of Orange County.

The homemade dishes weren't the only thing to look forward to, however. In another building, Sandy Jacobs, volunteer event coordinator, and her team set up a kitchen quiz for members. On several tables, there were different cooking tools and participants were challenged to name as many tools as they could. 

In another classroom, while some members were presenting food, others presented their themed table setting décor. Participants had to prepare a complete table setting entry including a menu card, centerpiece and table settings for two. Judges considered creativity, use of color, table setting etiquette, knowledge in talking to the judges, and appearance in their evaluation. 

Finally, to wrap up the day, members competed in a cupcake decorating competition. Participants were responsible for bringing their own supplies including tools and edible decorations for Cupcake Wars. Depending on their age group, participants had 20 minutes to decorate two to four cupcakes, each of a different theme.

To learn more about 4-H in Orange County, visit https://oc4h.org/.

4-H members participating in Cupcake Wars are tasked with decorating cupcakes according to a certain theme and presenting them to judges.

Food waste, nutrition in prison focus of webinars Feb. 22, 29

Free webinars about food waste and nutrition in correctional systems will be presented by the University of California Agriculture and Natural Resources.

The UC ANR Sustainable Food Systems Emerging Issues Webinar Serieswill first cover food waste on Feb. 22.

“The Sustainable Food Systems strategic initiative panel aimed to highlight innovative solutions to emerging issues within the food system from field-to-fork,” said Danielle Lee, UC Nutrition Policy Institute director of communications and research engagement.

“Over one-third of all available food in the U.S. is uneaten through food loss or waste – totaling up to over $160 billion – which has negative impacts on food security and the climate,” she said. “Households could save over $370 per person each year by reducing or preventing food waste. Additionally, when uneaten food ends up in the landfill, it generates greenhouse gases, and landfills are now the third largest producers of methane in the U.S.”

“California's adoption of SB 1383 aims to solve these problems,” Lee said. “You'll meet experts who are implementing consumer education and organic waste recycling programs aligned with SB 1383.” 

The second 90-minute webinar, on Feb. 29, will focus on nutritious foods for residents of correctional facilities.

“We chose incarcerated people as our case study population for two reasons – the California Department of Corrections and Rehabilitation is the single largest public purchaser of food in the state and studies have shown that 63% of incarcerated individuals rarely or never have fresh vegetables and 55% rarely or never have fresh fruit.”

California has two policies that can support institutional procurement of fresh produce – AB 822 and AB 778.

“The Harvest of the Month program is an innovative solution to implementing these policies while supporting improved nutrition security for incarcerated individuals,” Lee said. “Prison gardening programs can not only provide therapeutic benefits to residents, but also reduce recidivism rates and serve as workforce development opportunities to better prepare residents for returning to their communities post-incarceration.”

Heile Gantan of Impact Justice, second from left, and Ron Strochlic of Nutrition Policy Institute (plaid shirt) chat with residents of California State Prison Solano about the quality of their food.

Part 1 - Harvesting Solutions: A Trio of Perspectives on Addressing Food Waste from Field to Fork

Thursday, Feb 22, at 10-11:30 a.m. PT 

To minimize food waste, three experts explore factors influencing food loss and waste, delve into innovative recycling techniques, and explore statewide initiatives targeting household food waste. Experts in postharvest handling, food waste recycling and community education will share research findings and strategies.

Agenda:

• An overview of food waste in fruits and vegetables
  Deirdre Holcroft, Holcroft Postharvest Consulting
• Exploring means to extract embodied energy and lower greenhouse gas emissions in food waste recycling
  Michael Cohen, UC Cooperative Extension organic materials management and agri-food systems advisor for Santa Clara County
• The opportunities in statewide programs in reducing household food waste: Results from UC ANR household food practice needs assessment
  Yu Meng, UC Cooperative Extension youth, family and community advisor in Riverside, San Bernardino and Imperial counties

Part 2 - Farm to Corrections: Cultivating Justice through Nutrition and Gardening Initiatives

Thursday, Feb. 29, at 10-11:30 a.m. PT

Experts share insights on groundbreaking initiatives for justice-involved individuals' access to California-grown produce and nutrition and gardening education. Innovative initiatives such as a “Harvest of the Month” program by the California Department of Corrections and Rehabilitation in collaboration with the UC Nutrition Policy Institute and Impact Justice aim to increase access to fresh, locally grown fresh fruits and vegetables and trauma-informed nutrition workshops. They also highlight the impact of UC Master Gardener projects on rehabilitation and workforce development.

Agenda:

• Produce during and after prison: Increasing justice-impacted individuals' access to California-grown produce and nutrition education
  Carolyn Chelius, UC ANR Nutrition Policy Institute; Heile Gantan, Impact Justice; Lance Eshelman, California Department of Corrections and Rehabilitations
• UC Master Gardeners Prison Gardens Projects
  Missy Gable, director of the UC Master Gardener Program

Learn more and register at https://ucanr.edu/sites/StrategicInitiatives/Sustainable_Food_Systems/Events.

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