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Open Access Publications from the University of California


California Agriculture is a quarterly peer-reviewed journal reporting research, reviews and news on California’s agricultural, natural and human resources.

Volume 75, Issue 3, 2021

Issue cover
Cover Caption:Mowing of winter cover crop with a flail mower in a long-term National Research Initiative study of conservation agriculture systems at the UC West Side Research and Extension Center in Five Points, Calif. Cover cropping is an important soil health management practice that has been monitored at the Five Points site. A recent study of sorghum and garbanzo yields in the San Joaquin Valley examined the effects of cover cropping and no-till techniques versus no cover crop and standard tillage

Research and Review Articles

Silviculture can facilitate repeat prescribed burn programs with long-term strategies

A significant expansion of prescribed fire activity will be necessary to mitigate growing wildfire hazard in California forests. Forest managers can facilitate this expansion by promoting forest structures that allow for more effective implementation of prescribed fire, for both initial-entry and repeat burns. We analyzed changes in surface fuel during a series of three burns in replicated mixed-conifer stands following a period of over 100 years of fire suppression and exclusion. Total fuel load, proportion of pine present, canopy cover and basal area of live trees were relevant forest-structure components that influenced plot-scale fuel consumption. The study highlighted the importance of pre-fire fuel load and the relative proportion of pine in the overstory, which both led to greater amounts of fuel consumption. The initial-entry burn dramatically reduced all fuel categories (fine fuel, coarse wood and duff). Following each burn, fuel recovered until the next burn reduced loads enough to maintain low fuel levels. We apply the results to provide an example of how to determine the timing of prescribed fires.

No-tillage sorghum and garbanzo yields match or exceed standard tillage yields

To meet the requirements of California's Sustainable Groundwater Management Act, there is a critical need for crop production strategies with less reliance on irrigation from surface and groundwater sources. One strategy for improving agricultural water use efficiency is reducing tillage and maintaining residues on the soil surface. We evaluated high residue no-till versus standard tillage in the San Joaquin Valley with and without cover crops on the yields of two crops, garbanzo and sorghum, for 4 years. The no-till treatment had no primary or secondary tillage. Sorghum yields were similar in no-till and standard tillage systems while no-till garbanzo yields matched or exceeded those of standard tillage, depending on the year. Cover crops had no effect on crop yields. Soil cover was highest under the no-till with cover crop system, averaging 97% versus 5% for the standard tillage without cover crop system. Our results suggest that garbanzos and sorghum can be grown under no-till practices in the San Joaquin Valley without loss of yield.

Addressing organizational climate can potentially reduce sexual harassment of female agricultural workers in California

Workplace sexual harassment (SH) has been highlighted as a key issue for female agricultural workers in the United States. This study investigated how workers' descriptive data (age, job experience, attitudes) and specific organizational variables (how work crews are structured) potentially facilitate SH in an agricultural setting. Harassment was reported by 30% of surveyed female viticulture workers in their current jobs. Harassed women tended to be younger, employed seasonally and working in crews where hostile sexist views were prevalent. Harassment affected worker productivity; harassed women and their male co-workers were less satisfied with their jobs and more likely to seek other employment. Efforts to address SH by restructuring at the level of the field crew may be ineffective. Instead, addressing workers' hostile sexist attitudes and the extent to which an organization tolerates SH appears to have the most promise for reducing SH in agricultural industries.

Biological and chemical pruning wound protectants reduce infection of grapevine trunk disease pathogens

Grapevine trunk diseases (GTDs) are currently considered some of the most important challenges for viticulture, curtailing vineyard longevity and productivity in nearly every raisin, table and wine grape production region in California and worldwide. Pruning wounds provide the main entry point for fungal pathogens responsible for these diseases; pathogens enter the wounds following precipitation events. The aim of this study was to evaluate the efficacy of selected chemical and experimental biological fungicides for protection of pruning wounds against two of the most common and virulent fungal pathogens causing GTDs: Eutypa lata and Neofusicoccum parvum. This study was conducted on sauvignon blanc at the UC Davis Department of Plant Pathology Field Station. Results showed that several chemical and biological fungicides, notably the chemical fungicide Luna Sensation, the biofungicide Vintec and a combination of the biofungicides Bio-Tam and CrabLife Powder, provided significant protection against at least one of the two canker pathogens used in this study. However, the majority of products tested did not provide simultaneous control of both E. lata and N. parvum pathogens, highlighting the continuing challenge of controlling GTDs.

Proposed changes to the H-2A program would affect labor costs in the United States and California

The H-2A visa program allows farmers in the United States to be certified by the U.S. Department of Labor to recruit and employ guest workers, usually for a maximum of 10 months, when they are unable to find enough workers living in the United States (including U.S. citizens, other legally authorized workers, and workers not authorized to work in the United States). We analyzed U.S. and California H-2A job certification data to determine how the program is currently used and how a proposed H-2A wage freeze would likely affect future farm labor costs. Our analysis suggests that changes in the H-2A visa program would likely expand the program while reducing labor costs in California and elsewhere.

Vineyard-specific climate projections help growers manage risk and plan adaptation in the Paso Robles AVA

California's wine grape growers will face increasing challenges under a changing climate as most production occurs near the boundaries of current varieties' climatic thresholds. As part of this study, we developed a method for transforming downscaled climate information from the publicly available Cal-Adapt database into useful and useable climate projections for vineyard managers and advisors in the Paso Robles American Viticultural Area. We shared vineyard-specific projections during interviews of 20 managers and advisors. Overall, interviewees expressed trust in the projections and found them helpful in reducing their psychological distance from climate change. The projections prompted consideration of strategies for managing future climate risk and planning adaptation, with the majority of adaptations associated with long-term decisions such as row orientation, variety selection, dry farming, crop diversification and relocation. Agri-climatic decision support tools such as the one prototyped here may prove especially helpful for incorporating climate adaptation into the long-term business planning and vineyard redevelopment decisions facing managers and advisors in the near future. This approach could be extended to other California wine grape regions or to other perennial crops with expected vulnerabilities to climate change.

Low prevalence of handwashing and importance of signage at California county fair animal exhibits

Disease outbreaks among visitors at venues where animals are exhibited, such as animal shows at county fairs or petting zoos, are national public health concerns. Zoonotic disease transmission at fairs can occur through a variety of pathways, including direct contact with livestock and indirect exposure through contact with animals' immediate surroundings. Handwashing can reduce pathogen transmission. The goal of this observational study was to determine rates of handwashing among county fair visitors and to learn whether signage and/or contact with animals were correlated with handwashing practice. The investigation was conducted at four county fairs located across two geographic regions of California. Observations occurred over the course of one summer. Results from our observations of fair visitors revealed a low overall prevalence (5%) of handwashing behavior. However, fair visitors who made contact with animals were more likely to wash their hands. Additionally, those individuals who walked through barns where handwashing signage was present were significantly more likely to wash their hands than those who visited barns without signage.