Archive

Restoring hedgerows, or other field edge plantings, to provide habitat for bees and other beneficial insects on farms is needed to sustain global food production in intensive agricultural systems. To date, the creation of hedgerows and other restored habitat areas on California farms remains low, in part because of a lack of information and outreach that addresses the benefits of field edge habitat, and growers' concerns about its effect on crop production and wildlife intrusion. Field studies in the Sacramento Valley highlighted that hedgerows can enhance pest control and pollination in crops, resulting in a return on investment within 7 to 16 years, without negatively impacting food safety. To encourage hedgerow and other restoration practices that enhance farm sustainability, increased outreach, technical guidance, and continued policy support for conservation programs in agriculture are imperative.

California's Mediterranean agro-ecosystems are a major source of U.S. fruits and vegetables, and vulnerable to future extremes of precipitation and temperature brought on by climate change, including increased drought and flooding, and more intense and longer heat waves. To develop resilience to these threats, strategies are necessary for climate-smart management of soil and water. Long-term, large-scale, replicated ecological experiments provide unique testbeds for studying such questions. At the UC Davis Russell Ranch Sustainable Agriculture Facility (RRSAF), the 100-year Century Experiment, initiated in 1992, is investigating the effects of multiple farming practices in a farm-scale replicated study of 10 row crop cropping systems. It includes different fertility management systems: organic, conventional and hybrid (conventional plus winter cover crop) systems; different crops: wheat, tomatoes, corn, alfalfa, cover crops and grasslands; and different irrigation systems: rainfed, flood irrigated and drip irrigated. We briefly describe and report on a selection of long-term experiments conducted at RRSAF investigating soil management and irrigation practices, which are an important focus for developing climate-smart strategies in Mediterranean systems. For example, long-term monitoring of soil carbon content revealed that most crop systems have experienced a small increase in soil carbon since 1993, and increases in organically managed plots were substantially higher. As RRSAF continues to build upon this rich dataset from one of a very few long-term row crop experiments in Mediterranean ecosystems, it provides a testbed for identifying climate-smart solutions for these agronomically important ecosystems.

Since 2012, the UC Sustainable Agriculture Research and Education Program (SAREP) has worked with the Yolo County Department of Agriculture to support farm to school activities in Yolo County. In 2015, SAREP partnered with the Yolo County Department of Agriculture to deepen engagement with Yolo County growers and increase direct sales to Yolo County schools. SAREP tracked the volumes and prices of produce purchased by five school districts for the 2014–2015 baseline year and the 2015–2016 school year. Analysis was completed for three school districts for common produce items purchased, increases in in-season purchasing and direct grower versus distributor sales. For these districts, 17 produce items were in the top 10 for at least one of the districts; the five most common were apples, bananas, lettuce, oranges and strawberries, four of which are available locally for some or all of the school year. Districts purchased between 50% and 75% of their produce in season by the end of year two. All districts increased their purchases directly from growers. Findings suggest how services for growers and school food buyers can contribute to more local procurement.

A recent University of California (UC) systemwide survey showed that 42% of UC college students experience food insecurity, consistent with other studies among U.S. college students. As part of UC's efforts to understand and address student food insecurity, we conducted 11 focus group interviews across four student subpopulations at UC Los Angeles (n = 82). We explored student experiences, perceptions and concerns related to both food insecurity and food literacy, which may help protect students against food insecurity. Themes around food insecurity included student awareness about food insecurity, cost of university attendance, food insecurity consequences, and coping strategies. Themes around food literacy included existing knowledge and skills, enjoyment and social cohesion, and learning in the dining halls. Unifying themes included the campus food environment not meeting student needs, a desire for practical financial and food literacy “life skills” training, and skepticism about the university's commitment to adequately address student basic needs. The results of this study broadly suggest there is opportunity for the university to address student food insecurity through providing food literacy training, among other strategies.

The informal economy, healthy food options and alternative urban food systems are interconnected in important ways. To better understand these connections, and explore a rooted university approach to working with communities, we collaborated with the San Diego Community Garden Network to analyze the production, distribution and consumption of produce from eight community gardens in San Diego County. The project engaged UC San Diego researchers and students with county residents and community-based organizations to develop a survey together. Interviews with the gardeners and data from the completed survey document the ways in which community gardens contribute to individual and household health, well-being and community development. They suggest that despite perceptions that community gardens have marginal commercial capacity, they have the potential to contribute in meaningful ways to community development, particularly in low-income neighborhoods.

Of the greenhouse gases emitted from cropland, nitrous oxide (N₂O) has the highest global warming potential. The state of California acknowledges that agriculture both contributes to and is affected by climate change, and in 2016 it adopted legislation to help growers reduce emissions of greenhouse gases, explicitly including N₂O. Nitrous oxide emissions can vary widely due to environmental and agronomic factors with most emission estimates coming from temperate grain systems. There is, however, a dearth of emission estimates from perennial and vegetable cropping systems commonly found in California's Mediterranean climate. Therefore, emission factors (EFs) specific to California conditions are needed to accurately assess statewide N₂O emissions and mitigation options. In this paper, we review 16 studies reporting annual and seasonal N₂O emissions. This data set represents all available studies on measured emissions at the whole field scale and on an event basis. Through this series of studies, we discuss how such farm management and environmental factors influence N₂O emissions from California agriculture and may serve as a basis for improved EF calculations.

Agriculture in California contributes 8% of the state's greenhouse gas (GHG) emissions. To inform the state's policy and program strategy to meet climate targets, we review recent research on practices that can reduce emissions, sequester carbon and provide other co-benefits to producers and the environment across agriculture and rangeland systems. Importantly, the research reviewed here was conducted in California and addresses practices in our specific agricultural, socioeconomic and biophysical environment. Farmland conversion and the dairy and intensive livestock sector are the largest contributors to GHG emissions and offer the greatest opportunities for avoided emissions. We also identify a range of other opportunities including soil and nutrient management, integrated and diversified farming systems, rangeland management, and biomass-based energy generation. Additional research to replicate and quantify the emissions reduction or carbon sequestration potential of these practices will strengthen the evidence base for California climate policy.

In California, Asian citrus psyllid vectors the bacterium Candidatus Liberibacter asiaticus, which causes the lethal citrus disease huanglongbing. The top priority for California's citrus industry has been to diminish the rate of bacterium spread by reducing Asian citrus psyllid populations in urban areas, where this pest primarily resides. Attempts at eradicating and containing the psyllid with insecticides were unsuccessful. An alternative approach has been a classical biological control program using two parasitoids from Pakistan, Tamarixia radiata and Diaphorencyrtus aligarhensis, which attack the psyllid nymphs. T. radiata has established widely and, in combination with generalist predators, natural enemies are providing substantial control of psyllids in urban areas.

Verticillium dahliae is a soilborne fungus that is introduced to the soil via infested spinach seeds and that causes lettuce to be afflicted with Verticillium wilt. This disease has spread rapidly through the Salinas Valley, the prime lettuce production region of California. Verticillium wilt can be prevented or controlled by the grower by fumigating, planting broccoli, or not planting spinach. Because these control options require long-term investment for future gain, renters might not take the steps needed to control Verticillium wilt. Verticillium wilt can also be prevented or controlled by a spinach seed company through testing and cleaning the spinach seeds. However, seed companies are unwilling to test or clean spinach seeds, as they are not affected by this disease. We discuss our research on the externalities that arise with renters, and between seed companies and growers, due to Verticillium wilt. These externalities have important implications for the management of Verticillium wilt in particular, and for the management of diseases in agriculture in general.

2016 marked the year of the final phaseout of methyl bromide for use in strawberry production. During the long phaseout period, one replacement fumigant met so much public opposition it was taken off the market, while restrictions on use of other fumigants increased. As part of a larger study on the challenges facing the strawberry industry, I tracked fumigant use through California's pesticide use reporting system from 2004 to 2013. During the last few years before the phaseout, I interviewed 74 growers in the four main strawberry production regions about how they were now managing soilborne pests. As a general trend, growers had increased their use of chloropicrin and switched from broadcast fumigation to bed fumigation, and many were experimenting with organics. At the same time, significant percentages of growers were reluctant to change fumigation regimes or adopt nonchemical options of pathogen control. Some were unable to adopt less chemical-intensive methods because of land access conditions and land costs. Given these land-related obstacles, policymakers ought to consider strategies that will incentivize transitions to nonchemical alternatives and mitigate the financial risks.