This dissertation comprises three chapters, each dedicated to a separate issue facing the California agricultural industry and local communities. Chapter 1 evaluates the extent to which local land use impacts groundwater nitrate pollution. Nitrate pollution threatens human health and ecosystems in many regions of the world. Although scientists agree that nitrogen compounds from human activity, notably agriculture, enter groundwater systems, empirical estimates of the impacts of land use on nitrate concentrations in well water are still lacking. This paper provides evidence of such impacts by combining nitrate concentration measurements from 6,016 groundwater wells with remotely sensed California land use data from 2007--2023. Results show that a 10 percentage point increase in the share of land used to grow high nitrogen hazard index crops within 500 meters of a well relative to undeveloped land is associated with a 12\% increase in nitrate concentrations, while the same increase in low-intensity urban development is associated with a 10\% increase. Local cattle populations also contribute to nitrate pollution. However, conditioning on initial nitrate measurements, we find limited evidence that human activity affects nitrate concentrations a decade later.
Chapter 2 examines the adjustments farmers make to their pesticide programs in response to the Groundwater Protection Program, which created a natural experiment through abrupt and uneven changes in the regulations governing the application of seven pesticides. This paper utilizes twenty-five years of field-level data to estimate the program's impacts on the use of regulated active ingredients and the consequent environmental effects in the perennial crops almonds, citrus, and grapes using a difference-in-differences regression framework. The analysis reveals that the program led to meaningful reductions in the use of regulated active ingredients in fields in regulated regions, but the effects varied substantially across crops. To test if growers replaced regulated ingredients with alternative pesticides, we examine the impact of the program on the environmental impact---an index that considers the potential harm of pesticides to water systems, human health, and wildlife---of alternative active ingredients per planted acre and find no significant effects. In a final set of regressions, we use the environmental impact of regulated and alternative active ingredients per planted acre as our dependent variable and find that the program led to significant reductions in citrus orchards and grape vineyards but no change in almond orchards.
Chapter 3 evaluates the economic viability of Anaerobic Soil Disinfestation (ASD) in strawberry farming. ASD has emerged as a promising strategy for managing soilborne pests and pathogens among increasingly stringent regulatory restrictions on pre-plant soil fumigation. This study evaluates the economic viability of ASD in strawberry farming using partial budget analysis and data from field trials conducted in California during the 2021--2022 and 2022--2023 seasons. The analysis compares net returns (gross revenues minus analyzed costs) across ASD treatments and control plots, with and without chemical fumigation. Results from the 2021--2022 trial reveal no meaningful difference in yields from ASD-treated plots compared to control plots. Findings from the 2022--2023 trial show that ASD treatments significantly increased strawberry yields relative to non-fumigated control plots but yields from ASD with fumigation plots did not significantly differ from fumigated control plots. High ASD material, labor, and fumigation costs and low yields in the 2021--2022 trial resulted in negative and significantly smaller net returns from ASD treatments relative to the control. In the 2022--2023 trial, high yields among ASD plots resulted in positive net returns, but ASD treatment costs remained impractically high, leading to meaningfully smaller net returns from ASD treatments compared to the controls.
