Cool-season turfgrass response to biosolid fertilization in the Pacific Northwest

Jeff Alan Rutan

Turfgrass response to nitrogen (N) can be affected by N source and season of application. Field and laboratory studies were conducted at Puyallup, WA to compare turfgrass response measured by N recovery, visual color and quality, and N release of turfgrass fertilizers. Nitrogen sources were applied to a fine-fescue (Festuca rubra L.) / colonial bentgrass (Agrostis capillaris L.) mixture grown on a sand cap maintained under golf course fairway conditions and perennial ryegrass (Lolium perenne L.) grown on a Puyallup fine sandy loam soil maintained under home lawn conditions. In the field, month of application and N source were found to affect turfgrass response. Efficiency of ammonium sulfate (AmS), polymer-coated sulfur-coated urea (PCSCU), and biosolid N sources was increased when applications were made corresponding to plant growth cycles and periods of expected active microbiological activity. Effective late fall N use from biosolid fertilization of perennial ryegrass was noted. Limited availability of complex N forms associated with biosolid N sources produced overall less turfgrass response. However, similar turfgrass response to N sources was noted when higher biosolid N rates were applied to perennial ryegrass turf. Generally N recovery and visual quality were highest 4 wk after N source application. A laboratory incubation study was conducted to compare N release rates of fertilizers containing various organic N sources. Product composition appeared to have an effect on inorganic N release (NH4 + + NO3 - ). As N solubility increased, total N extracted increased. A large fraction of inorganic N was collected after the first week of incubation. Nitrogen source affected the amount of inorganic N released. Higher amounts of inorganic N were extracted from AmS and PCSCU fertilizers while less was extracted with Nutri-Rich 4, Milorganite® and Soundgro™. Inorganic N release was found similar for anaerobically digested biosolids and dried poultry waste alone. Inorganic N release was better estimated via fertilizer C:N ratio than N source materials. Seasonal turfgrass response and N availability are important factors to consider when selecting N fertilizers. Higher rates of applied biosolids may be needed to account for decreased first year N availability.

Cool-season turfgrass response to biosolid fertilization in the Pacific Northwest

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