California Agriculture Research Articles

The Tree-Crop Remote Sensing of Evapotranspiration Experiment (T-REX): A Science-Based Path for Sustainable Water Management and Climate Resilience

Abstract Water scarcity threatens agriculture in California. During the last two decades, historically severe droughts have led to severe water shortages. Under projected changes in climate, droughts of greater severity and duration will exacerbate this situation. California produces 80% of the world’s almonds, which require consistent water supplies for irrigation. Almonds are the most commonly grown crop in California, covering nearly 1.4 million acres over about 8,000 farms. In response to these challenges, almond growers are considering a myriad of management strategies to save water and mitigate climate change. The Tree-Crop Remote Sensing of Evapotranspiration Experiment (T-REX) aims to identify water and orchard management opportunities to maximize water use efficiency and carbon sequestration in almonds and other woody perennial tree crops. The project combines satellite, uncrewed aerial vehicles, and proximal sensing technologies to retrieve key variables used to model surface fluxes and biophysical properties. We aim to advance our understanding of water management and cultural practices on water–carbon relationships in tree-perennial agroecosystems. Through new methods, such as evapotranspiration-based irrigation scheduling, even a modest 10% decrease in almond orchard irrigation across the state equates to about a third of the water in Lake Oroville, California’s second-largest reservoir, at average levels. From a carbon perspective, almond orchards could sequester 8% of the state’s current greenhouse gas emissions by transitioning toward climate-smart practices. As such, the almond industry is uniquely positioned to curb water use and contribute to climate change mitigation while maintaining economic viability of almond production. An overview of initial results related to evapotranspiration observational and modeling uncertainty and carbon sequestration potential are presented in this article.

Classics in human geography revisited: Julie Guthman’s Agrarian Dreams: The Paradox of Organic Farming in California

Classics in human geography revisited: Julie Guthman’s Agrarian Dreams: The Paradox of Organic Farming in California

The Modern Portrait of The American Family in Sam Shepard's True West

Sam Shepard (1943-2017) was born to Sam Rogers the sixth and Jane Elaine Schook Rogers on Nov. 1943 in Fort Sheridan, Illinois. To keep the family tradition, he was nicknamed Steve to distinguish him from his father who was a military man. The family was moving from a place to another before staying in a farm in California where they raised sheep and grew avocados. At the age of eleven and while Shepard was studying at school, he received a copy of Samuel Beckett's Waiting For Godot from one of his friends which was a new experience for him. In 1963, Shepard moved to New York where his talent of writing developed. He found himself in the middle of a rapidly transforming social and cultural world. At that time, he changed his name from Steve Rogers to Sam Shepard to break his heredity of the name and to distance himself from the ties of the family. He was awarded the Pulitzer Prize in 1978 due to his masterpiece Buried Child.

Effect of a dairy farmworker stewardship training program on antimicrobial drug usage in dairy cows

Antimicrobial use (AMU) is critical to preserving animal health and welfare. However, the development of antimicrobial resistance (AMR) represents a public health threat. Although most antimicrobials used on the farm require a veterinarian prescription, farmworkers make daily on-farm treatment decisions. Therefore, farmworker training is vital to promote responsible AMU. This research project aimed to evaluate the effect of farmworker antimicrobial stewardship (AMS) training on the quantity of AMU on dairy farms in Ohio and California. We hypothesized that farms receiving AMS training would have reduced AMU in dairy cattle compared with farms where training wasn't administered. We designed a quasiexperimental study with 18 conventional dairy farms enrolled in Ohio and California. Twelve farms received AMS training, and 6 farms did not. The AMS program included a 12-wk training focused on accurate identification of cows requiring antimicrobial treatment. We quantified AMU by collecting used drug containers, manually counted by researchers during farm visits. Treatment incidence (TI) was calculated using animal daily doses (ADD), and Poisson regression models were used to analyze the TI data. Disease incidence rate (DIR) in lactating cows was 2.2, 1.5, 1.0, 0.4, 0.3, 0.2, and 0.03/1,000 cow-days for mastitis, lameness, metritis, pneumonia, retained placenta, diarrheas, and other diseases (e.g., conjunctivitis, injuries), respectively. The highest TI by antimicrobial class (provided in ADD/1,000 cow-days) was cephalosporin (5.9), penicillin (5.2), tetracyclines (0.4), lincosamides (0.2), and sulfonamides (0.1). Among the trained farms using a within-treatment group analysis, no significant differences were observed in TI pre-intervention (10.9 ADD/1,000 cow-days) compared with TI postintervention (10.3 ADD/1,000 cow-days). Treatment incidence from the training group was 10.8 ADD/1,000 cow-days and although numerically lower, it was not significantly different compared with TI in the control groups at 13.9 ADD/1,000 cow-days (rate ratio = 0.77, CI = 0.25-2.38). Future research on AMS should incorporate farmworker training with social science approaches to overcome barriers and promote on-farm responsible use.

Adaptation and sustainability: Lessons from Central Coast organic farmers during the pandemic

The challenges faced by organic vegetable farmers in California during the COVID-19 pandemic included uncertainty about food safety rules and best practices, availability of workers, and significant changes to their markets. When the pandemic began, we built on an ongoing interdisciplinary research project with organic vegetable farmers on the California Central Coast to track how those growers adapted to the crisis. We conducted surveys in April 2020 and January 2021 to determine impacts on farmers and how farm size, market channels, and management strategies influenced a farm's ability to adapt to and recover from pandemic-induced disruptions. We found that mid-sized farmers with flexible and diverse marketing channels could navigate changes from the pandemic with minimal losses and, in some cases, economic gains. By contrast, smaller farmers with limited resources, especially those with disadvantaged backgrounds and limited access to technology, experienced more drastic impacts, including lost markets, labor shortages, and increased childcare needs. The lessons learned can inform a transition toward more sustainable, resilient agroecological systems.

Geographical survey of the mycobiome and microbiome of Southern California glassy-winged sharpshooters.

The glassy-winged sharpshooter, Homalodisca vitripennis Germar, is an invasive xylem-feeding leafhopper with a devastating economic impact on California agriculture through transmission of the plant pathogen, Xylella fastidiosa. While studies have focused on X. fastidiosa or known symbionts of H. vitripennis, little work has been done at the scale of the microbiome (the bacterial community) or mycobiome (the fungal community). Here, we characterize the mycobiome and the microbiome of H. vitripennis across Southern California and explore correlations with captivity and host insecticide resistance status. Using high-throughput sequencing of the ribosomal internal transcribed spacer 1 region and the 16S rRNA gene to profile the mycobiome and microbiome, respectively, we found that while the H. vitripennis mycobiome significantly varied across Southern California, the microbiome did not. We also observed a significant difference in both the mycobiome and microbiome between captive and wild H. vitripennis. Finally, we found that the mycobiome, but not the microbiome, was correlated with insecticide resistance status in wild H. vitripennis. This study serves as a foundational look at the H. vitripennis mycobiome and microbiome across Southern California. Future work should explore the putative link between microbes and insecticide resistance status and investigate whether microbial communities should be considered in H. vitripennis management practices. IMPORTANCE The glassy-winged sharpshooter is an invasive leafhopper that feeds on the xylem of plants and transmits the devastating pathogen, Xylella fastidiosa, resulting in significant economic damage to California's agricultural system. While studies have focused on this pathogen or obligate symbionts of the glassy-winged sharpshooter, there is limited knowledge of the bacterial and fungal communities that make up its microbiome and mycobiome. To address this knowledge gap, we explored the composition of the mycobiome and the microbiome of the glassy-winged sharpshooter across Southern California and identified differences associated with geography, captivity, and host insecticide resistance status. Understanding sources of variation in the microbial communities associated with the glassy-winged sharpshooter is an important consideration for developing management strategies to control this invasive insect. This study is a first step toward understanding the role microbes may play in the glassy-winged sharpshooter's resistance to insecticides.

Urban agriculture in California: Lessons learned from an urban farmer workshop series

Urban farming is an important component of California agriculture, but lack of agricultural census data or common definitions makes it difficult to track and understand. In 2017–2018, a team of University of California Agriculture and Natural Resources (UC ANR) researchers and extension professionals developed a workshop series for urban farmers in California based on results of a prior needs assessment. After conducting 16 workshops in the state's largest urban centers, the team evaluated what participants learned and how they put their knowledge into action. The evaluation highlighted urban farmers' ongoing challenges and found that economic issues such as profitability and land access are some of the greatest barriers for urban farming in California. An unexpected positive outcome was the opportunity for participants to network and meet other farmers. Urban farmers expressed the need for more opportunities for mentoring and building partnerships with other farmers and organizations. Evaluation results suggest that California's urban farmers may be more diverse than California farmers as a whole, and that they are often beginning farmers.

Detection and virulence of Lactococcus garvieae and L. petauri from four lakes in southern California.

The first objective of the study aimed to detect the presence of Lactococcus petauri, L. garvieae, and L. formosensis in fish (n = 359) and environmental (n = 161) samples from four lakes near an affected fish farm in California during an outbreak in 2020. The second objective was to compare the virulence of the Lactococcus spp. in Rainbow Trout Oncorhynchus mykiss and Largemouth Bass Micropterus salmoides. Standard bacterial culture methods were used to isolate Lactococcus spp. from brain and posterior kidney of sampled fish from the four lakes. Quantitative PCR (qPCR) was utilized to detect Lactococcus spp. DNA in fish tissues and environmental samples from the four lakes. Laboratory controlled challenges were conducted by injecting fish intracoelomically with representative isolates of L. petauri (n = 17), L. garvieae (n = 2), or L. formosensis (n = 4), and monitored for 14 days postchallenge (dpc). Lactococcus garvieae was isolated from the brains of two Largemouth Bass in one of the lakes. Lactococcus spp. were detected in 14 fish (8 Bluegills Lepomis macrochirus and 6 Largemouth Bass) from 3 out of the 4 lakes using a qPCR assay. Of the collected environmental samples, all 4 lakes tested positive for Lactococcus spp. in the soil samples, while 2 of the 4 lakes tested positive in the water samples through qPCR. Challenged Largemouth Bass did not show any signs of infection postinjection throughout the challenge period. Rainbow Trout infected with L. petauri showed clinical signs within 3 dpc and presented a significantly higher cumulative mortality (62.4%; p < 0.0001) at 14 dpc when compared to L. garvieae (0%) and L. formosensis (7.5%) treatments. The study suggests that qPCR can be used for environmental DNA monitoring of Lactococcus spp. and demonstrates virulence diversity between the etiological agents of piscine lactococcosis.

More jobs and less seasonal employment in California agriculture since 1990

Employment in California agriculture has increased over the past 30 years and has become less seasonal. There were an average of 404,000 farm jobs in California in 2020, 10% more than average employment of 367,000 in 1990. Meanwhile, seasonality, as measured by peak month employment divided by trough month employment, fell 22% over three decades, from 1.8 in 1990 to 1.4 in 2020. Most farmworkers have one farm employer a year, although that employer may be a labor contractor who moves workers from one farm to another. Most new workers in the California farm workforce are H-2A guest workers, the young and flexible Mexican workers who are legally authorized to work in the United States and who are often brought to farms by labor contractors. In the future, rising employment and declining seasonality, combined with an aging and settled farm workforce, may reduce farmworker migration and flexibility.

How agritourism helped farmers during the pandemic

During COVID-19, California small farmers and ranchers suffered significant disruptions and shifts in the marketplace, marked by a loss in wholesale outlets and an increase in demand for direct-to-consumer sales. This study examines how agritourism operators responded to the challenges and opportunities created by the pandemic. In 2021 and 2022, in the midst of the pandemic, the UC ANR Agritourism Program held a series of trainings for California farmers interested in starting or expanding agritourism enterprises. Some of the key themes that emerged from the trainings were that farmers had to shift their operations to ensure social distancing and reduced crowd sizes, while at the same time, they experienced an unprecedented demand for direct-to-consumer sales and on-farm visits. Agritourism, in varying degrees, contributed to the resiliency of most of the participants in our study. Moving forward, it would be worthwhile for researchers, agricultural professionals, and decision-makers to examine equity in agritourism and agritourism's role as a risk-management strategy to help mitigate other types of disruptions in the future. Our findings also point to the need to provide farmers with technical assistance around e-commerce and sustainable business planning.

Intergenerational family farm leadership, organizational innovativeness, and resiliency

ABSTRACT Family farms are central to the American agricultural economy and vital inputs to the prosperity and sustainably of rural communities. Yet, the resiliency of these farms is threatened by uncertainties associated with intergenerational leadership succession. The current study used a set of theoretical constructs from Rogers’s (2003) Innovation Diffusion Model (centralization, formalization, interconnectedness, organizational slack, size) to guide a qualitative exploration of the implications of intergenerational leadership dynamics on the organizational innovativeness of six family farms in California’s San Joaquin Valley. Three themes emerged across all six farms that bring nuance and complexity to the understanding of organizational innovativeness and intergenerational leadership dynamics within family farms. The themes together reveal the importance of routine ingenuity, the honoring of legacy, and conservative innovation on the longer-term resiliency of intergenerational family farms and the community systems in which they are positioned.

Quantification of antimicrobial usage on dairy farms before, during and after the implementation of farmworker stewardship training

Antimicrobials are critical to preserving animal health and welfare. However, the development of antimicrobial resistance represents a public health threat. Veterinarians prescribe an­timicrobials, but farmworkers are responsible for making on-farm treatment decisions and their training is vital to promote responsible antimicrobial use (AMU). This research project aimed to describe and quantify AMU on large dairy farms in Ohio and California and evaluate the impact of farmworker antimicrobial stewardship (AMS) training on those metrics. We hypothesized that farms, where AMS training was adminis­tered, would have significantly lower AMU compared to farms where training was not administered.

Farmer Adoption of Climate-Smart Practices Is Driven by Farm Characteristics, Information Sources, and Practice Benefits and Challenges

Agriculture plays an important role in mitigation and adaptation to climate change. Yet, advances in climate-smart agriculture require a better understanding of farmer adoption. This exploratory paper uncovered differences that distinguish High, Moderate, and Low adopters of climate-smart practices. Our study utilized 952 in-person surveys of California farmers with a focus on mitigation and adaptation practices, along with farm characteristics, information sources, and practice benefits and challenges. Specifically, farmers with larger parcels were more likely to be High adopters, and farmers with access to only one water source were more likely to be Low adopters. There was no significant difference found between Moderate and High adopters’ use of any information sources. The ranking of different information sources changed between groups. Furthermore, there was no significant difference in the rate of Moderate and High adopters’ consideration of practice benefits. All groups identified practice uncertainty as the greatest challenge, with a significant difference between Moderate and High adopters. Our results demonstrate where differences occur between farmer adopter groups and by extension provide insights into where to target outreach efforts to promote the adoption of climate-smart practices in California agriculture.

Three decades of “Africanized” honey bees in California

“Africanized” honey bees (AHB) have been part of California's agricultural and natural landscapes for nearly three decades. Prior to their arrival in 1994, leading honey bee experts expressed concern over the potentially disastrous impact of AHB on California agriculture and public safety. Despite these concerns, the state's agricultural production has not been significantly impacted by AHB. However, some evidence suggests that the abundance of AHB in natural habitats can have negative consequences for native pollinators. At the same time, AHB may provide a genetic resource for improving managed honey bee health. We recommend updating the term “Africanized” honey bees to more accurately reflect their biology and to avoid unfortunate connotations.

Long-term reduced tillage and winter cover crops can improve soil quality without depleting moisture

California farmers who use reduced-disturbance tillage and winter cover cropping can boost production and improve soil health. However, some farmers are hesitant to try these conservation practices due to uncertainty about whether planting winter cover crops will deplete soil moisture in already drought-stricken regions. Our study addresses these concerns by looking at how long-term reduced-disturbance tillage and winter cover cropping, compared to fallowed soils with standard tillage, affected soil moisture. Although we found a statistical difference in total soil water content, the difference was only about 0.3 inches of water per foot of soil. On average, the soil water content of the top 0–96 inches was highest for the reduced-disturbance fields with winter cover crops. This was especially evident during our driest field season, from November 1, 2017, to March 15, 2018, when cumulative rainfall was only 1.9 inches. Our findings show that winter cover cropping and reduced-disturbance tillage can improve soil without depleting soil water levels in row crops.

Technical Assistance Providers Identify Climate Change Adaptation Practices and Barriers to Adoption among California Agricultural Producers

Climate change will challenge California agriculture, requiring producers (i.e., farmers and ranchers) to adopt climate-adaptive management practices to sustain production. Agricultural technical assistance providers (TAPs) play a significant role in supporting producers’ efforts to adopt climate-smart management practices. It is therefore important to understand current TAP perceptions of climate change, TAP recommendations for climate adaptation, and the barriers to adopting climate-smart practices. To understand these issues, we held four focus group discussions with small groups of TAPs from across the state and evaluated transcripts from the discussions to identify common themes and concepts. The TAPs that participated in the focus groups understood climate change and its impacts on California agriculture, with climate extremes and water-related issues being the most frequently cited climate-related challenges. Focus group discussions and subsequent evaluation revealed that while TAPs recommend science-backed practices for adapting California agriculture to climate change, producers may not be accepting of some recommendations. Critically, the TAP focus groups cited insufficient monetary support—both for themselves and for producers—and insufficient information and messaging around climate-adaptive practices as key barriers to practice adoption. This improved understanding of the intersection of TAPs’ work on climate change and climate adaptation in California agriculture is useful for the development of information and resources that can bridge these identified barriers.

Water demands of permitted and unpermitted cannabis cultivation in Northern California

Illicit water use for irrigated agriculture can have substantial impacts on the environment and complicates water management decision-making. Water demand for illicit cannabis farming in California has long been considered a threat to watershed health, yet an accounting of cannabis irrigation has remained elusive, thereby impeding effective water policy for the state’s nascent legal cannabis industry. Using data obtained from both permitted and unpermitted cultivation operations, the current study applies novel water-use models to cannabis farms in Northern California to estimate their cumulative and relative water footprints. Our results indicated substantial variation in total water extraction volumes for cannabis farming between watersheds and that most cannabis water use was concentrated in a subset of watersheds, rather than evenly spread across the landscape. Water extraction volumes for unpermitted cannabis were consistently greater than permitted cannabis in the dry season, when streams are most vulnerable to impacts from water diversions. Results from scenario modeling exercises indicated that if all existing unpermitted farms were to become permitted and comply with regulations that prohibit surface water diversions in the dry season, nearly one third (34 of 115) of the study watersheds would experience a 50% reduction in dry season water extraction. In comparison, modest expansion of off-stream storage by all cannabis farms could reduce dry season extraction by 50% or greater in more than three quarters (96 of 115) of study watersheds. Combining diversion limits with enhanced storage could achieve dry season extraction reductions of 50% or greater in 100 of 115 watersheds. Our findings suggest that efforts to address the environmental impacts of unpermitted cultivation should focus on watersheds with greatest water demands and that programs that support expansion of off-stream storage can be helpful for reducing pressures on the environment and facilitating the transition of unpermitted farms to the regulated market.

Carbon farming can enhance pollinator resources

Native California bees and other wild pollinators, which are essential to many fruit and vegetable crops, are being threatened by climate change, pesticides and habitat degradation. Carbon farming, a set of practices that sequester carbon in the soil or woody biomass, can create habitat that supports these pollinators. This paper focuses on habitat management and farming practices that both increase carbon sequestration and benefit pollinator communities. By incentivizing and supporting conservation practices that incorporate carbon farming, we can protect wild pollinators and increase the resilience of California agriculture in the face of ongoing climate change.

Wind Speed and Landscape Context Mediate Campylobacter Risk among Poultry Reared in Open Environments.

Foodborne pathogens cause over 9 million illnesses in the United States each year, and Campylobacter from chickens is the largest contributor. Rearing poultry outdoors without the use of antibiotics is becoming an increasingly popular style of farming; however, little is understood about how environmental factors and farm management alter pathogen prevalence. Our survey of 27 farms in California, Oregon, Washington, and Idaho, USA, revealed a diversity of management practices used to rear poultry in the open environment. Here, we assess environmental and management factors that impact Campylobacter spp. prevalence in 962 individual chicken fecal samples from 62 flocks over a three-year period. We detected Campylobacter spp. in 250/962 (26.0%) of fecal samples screened, in 69.4% (43/62) of flocks, and on 85.2% (23/27) of farms. We found that Campylobacter spp. prevalence was predicted to increase in poultry on farms with higher average wind speeds in the seven days preceding sampling; on farms embedded in more agricultural landscapes; and in flocks typified by younger birds, more rotations, higher flock densities, and the production of broilers. Collectively, our results suggest that farms in areas with higher wind speeds and more surrounding agriculture face greater risk of Campylobacter spp. introduction into their flocks.

Development of sulfonated and aminated poly (ethylene-vinyl alcohol) nanofibrous membrane as a solid phase extraction matrix for trace metal ions preconcentration from dairy wastewater for direct ICP-OES analyses

A robust nanofiber-based adsorbent was developed as a potential solid phase extraction matrix for adsorption and preconcentration of Al3+, Ni2+, Cu2+ and Cd2+ ions. This adsorbent was developed by amination and sulfonation of eletrospun poly (ethylene-vinyl alcohol) nanofibrous membranes (SF-EVOH NFM). Possessing porous structure, abundant active amine and sulfonate groups, the SF-EVOH NFM showed static maximum adsorption capacities of 350, 180, 140 and 125 mg.g−1 for Al3+, Cu2+, Ni2+, and Cd2+, respectively. The varied metal affinities toward the NFM are determined by the structural features of the metal ions and the NFM. More significantly, the NFM showed a dynamic column adsorption ratio of 99% with a 97% recovery of metal ions, revealing the features of efficient adsorption and release of metal ions by the unique structures of the SF-EVOH NFM. Furthermore, the SF-EVOH NFM demonstrated excellent stability and recyclability for up to 10 cycles. The NFM was applied as a solid phase extraction (SPE) filter to preconcentrate metal ions from wastewater samples collected from dairy farms in Central Valley California, USA. The preconcentrated solution released from the SF-EVOH NFM filter adsorbents could be directly tested by an ion-coupled plasma optical emission spectroscopy (ICP-OES) with a limit of detection (LOD) of 0.025 mg.L−1 and a relative standard deviation (RSD) < 5% for Al3+, highlighting the excellent performance of the NFM for enhanced instrumental monitoring applications of wastewater samples.