Sustainable Management of Biogeochemical Cycles in Soils Amended with Bio-Resources from Livestock, Bioenergy, and Urban Systems

Bioresources are generated in a variety of environments and each presents unique risks and benefits associated with land application. Bioresources from livestock, urban and bioenergy systems were selected and evaluated through field, greenhouse and laboratory studies of potential risk and benefits of recycling to agricultural and urban landscapes. The waste stream, including feedstock sources and treatment processes, affects composition and properties of bioresources and effects on biogeochemical cycles of amended soils. Variation of decomposition and nutrient mineralization rates among bioresources used to amend soil for turfgrass and forage reflected variation among contrasting feedstock sources and treatments prior to application. During turfgrass establishment, plant available nitrogen and nitrogen mineralized from a bioresource from livestock waste streams, (Geotube! residual solids, supplied N in excess of crop uptake potential and contributed to leaching loss of N. In contrast, N mineralization rates from bioresources generated during methane production from dairy manure (manure solids) were not sufficient to maximize crop production, necessitating N fertilizer application. In addition to variation of composition, bioresource effects on crop productivity and environmental quality vary among management practices and between forage and turfgrass cropping systems. Large application rates of bioresources increase soil nutrient concentration and potential crop productivity, but contribute to increased nutrient loss in drainage and surface runoff. Yet, incorporation or Alum treatment of bioresources will reduce runoff loss of dissolved P and protect water quality without sacrificing crop productivity. Alum treatment of bioresources prior to land application effectively reduced runoff loss of dissolved P to levels observed for control soil. For situations in which large, volume-based bioresource rates are top-dressed or incorporated, export of applied nutrients environmental impacts were compared between forage and turfgrass systems. Starting during the initial year of production, annual export of applied N and P in Tifway bermudagrass sod was greater than export through forage harvests of Tifton 85. Low forage yield limited N and P export from Tifton 85 during the year of establishment, but increased forage yield during the second year increased export of manure N and P to levels more comparable to sod. As variation between compost sources, turfgrass and forage production systems, and application methods indicated, effective management of bioresources is necessary to balance benefits and risk in cropping systems. Integrated assessment of bioresource composition and crop-specific management of application method and rate will enable sustainable bioresource cycling and crop productivity.