Brown, SallyBeebe, Anna2021-10-292021-10-292021-10-292021Beebe_washington_0250O_23372.pdfhttp://hdl.handle.net/1773/48035Thesis (Master's)--University of Washington, 2021Biosolids and food scraps are highly prevalent in urban waste streams and can be stabilized for beneficial use as soil amendments. The impact of these amendments on soil health and crop response was tested for two urban soils. One soil was collected from the Tacoma Wastewater Treatment plant and was likely a remnant from plant construction. The second soil, a sandy loam, was classified as part of the Woodinville series (Fine-silty, mixed, super active, nonacid, mesic Aeric Fluvaquents) and collected from a farm located at the King County South treatment plant. Kale (Brassica oleracea ‘Winterbor’) and Swiss chard (Beta vulgaris ‘Fordhook Giant’) were grown in succession in a replicated pot trial. Pots were amended with high rates (220 mg ha-1) of two food scrap-based amendments; bokashi and vermicompost, and two biosolids-based materials; a potting soil (Tagro), and a sawdust/biosolids compost (GroCo). A soil-only control and an inorganic N-P-K (24-25-4) fertilizer control (224 kg N ha-1) were included. Soils were analyzed for total C and total N, pH, electrical conductivity (EC), mineralizable (min C), oxidizable carbon (POXC), and Mehlich-III (M-III) extractable nutrients. Plant response was measured via yield and foliar mineral concentrations (Ca, K, Mg, P, Cu, Fe, Mn, and Zn). Across both soils, organic amendments increased total C and total N, and reduced bulk density in comparison to both controls. In general, amendments increased soil available (M-III extractable) K, Mg, and S, and decreased Cu. Changes to soil C:N, pH, and M-III nutrients were mostly consistent with amendment characteristics. Measures of active C demonstrated positive changes to soil biological indicators but were not predictive of differences in plant yield. In the kale and chard, soil and amendment were highly significant factors for plant yield. Of the amendments tested, the Tagro and vermicompost resulted in dramatic improvements in plant yield and measured soil properties. Differences in yield as a result of amendment addition were more pronounced in the Tacoma soil and significantly higher than both controls. GroCo had positive effects on yield in both soils but was similar to the fertilized control in the Renton soil. The only case where bokashi germinated was for chard in the Renton soil. However, after successful germination, the yield was significantly higher than both controls and had the second-highest yield after vermicompost. This suggests further research should investigate the use of bokashi. Crops grown in the Tacoma soil had select foliar concentrations (P, S, Cu, Mn, and Zn) that were higher than in the Renton soil. Amendment impacts on yield in this soil would improve nutrients provided for an urban gardener relative to crops grown in amended soils in the initially higher-yielding soil (Renton). Overall, vermicompost, GroCo, and Tagro had similar or increased foliar macronutrients relative to the fertilized controls. Vermicompost had particularly large increases in crop K concentrations. Biosolids-based amendments had notably large increases in crop foliar concentrations of Mn and Zn in the chard. The results from this study suggest that food scrap-based residuals have the potential to improve urban soils and increase yields for urban agriculture.application/pdfen-USnonebiosolidsfood scrapsorganic amendmentssoil healthsoil qualityurban soilSoil sciencesEnvironmental scienceForestryThesis