Date of Award:

8-2022

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Melanie Stock

Committee

Melanie Stock

Committee

Paul Grossl

Committee

Grant Cardon

Abstract

Knowledge of both soil quality and contamination has become increasingly important with the growth of urban agriculture in Utah and the United States as whole. Land is also a common limiting factor in urban agriculture, so it is important to maximize yield and net returns. In order to meet these demands, three studies were conducted across key urban agriculture sites along the Wasatch Front: 1) an urban soil survey to assess soil contamination, 2) an urban soil survey to evaluate macronutrient and salinity levels, and 3) a nitrogen fertilizer management trial for dahlia (Dahlia pinnata), a cut flower crop with strong profit potential on urban microfarms. Urban agriculture sites included 31 farms and community gardens that were sampled from the fall of 2020 to spring of 2021 and analyzed for trace elements and hydrocarbon contamination, along with macronutrient levels and general soil quality parameters. Five nitrogen rates (0, 56,112, 168, and 224 kg ha-1) were tested in field trial for the yield and quality of dahlia ‘Café au Lait’ from 2019 to 2021 at the Utah Agricultural Experiment Station Greenville Research Farm. Urban soils were generally below the EPA regional screening limits (RSL) for trace element and hydrocarbon contaminants. However, the mean arsenic concentration was 17 times higher than the EPA RSL of 0.68 ppm, highlighting the need for a localized screening value to inform management practice. The macronutrient levels were above recommended levels across all surveyed sites, with mean soil test phosphorus three times greater than the recommended limit, indicating the need for nutrient management outreach with small, urban farmers and gardeners. Nitrogen management for dahlia was optimized with 168 kg N ha-1 application rates, though virus pressure impacted yields during the first two years of the study. Optimizing management and yield can provide urban farms with a high-value, non-edible food crop option on soils not suited for food production. Routine soil nutrient testing along with site screening for soil contamination is vital to maintaining long-term health and sustainability in urban agriculture.

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