Chemically-Treated Composted Biosolids Enhance Water Conservation and Quality on Urban Landscapes.

Incorporation of volume-based rates of composted biosolids (CB) enhances soil water retention and turf establishment compared to soil alone. Yet, high total P concentration in CB can increase extractable P in soil and loss of dissolved P in runoff and drainage from CB-amended soils. Chemical additives could be mixed with CB to reduce soluble P concentrations and potential P loss to surface waters. The objectives were to evaluate interactions among soil type, CB, chemicals additives, and runoff and drainage losses of P forms during turfgrass establishment over three simulated rain events. A randomized block design comprised three replications of eight establishment treatments. Controls were composed of Tifway Bermudagrass sprigged in each a calcareous and acidic soil. For the remaining six treatments, Tifway was sprigged after incorporation of untreated, Alum-treated (0.075 kg/kg), and CaOH-treated (0.029 kg/kg) CB within each soil type. The soils were packed into box lysimeters (45.5 x 33 x 20.7 cm) over a 5.7 cm depth of gravel. Simulated rainfall was applied for 30 minutes (10 cm/h) at 15, 30 and 60 days after planting. Analyses of runoff for each rain event indicated dissolved reactive P (DRP) concentration was similar between alum-treated CB amended soils (0.21 mg/L) and control soils (0.22 mg/L), but lower (p<0.05) than soil amended with CB or CaOH-treated CB. Samples of lysimeter drainage revealed similar effects of Alum on P loss during the second and third rain events. Mass loss of DRP in drainage from soil amended with alum-treated CB (1.494 mg/ha) was similar to control soil (2.501 mg/ha), and less (p<0.05) than untreated CB-amended soil (11.956 mg/ha). Results indicate that chemically treating CB with Alum prior to incorporation can limit DRP concentration or loss in runoff or drainage, permitting incorporation of volume-based CB rates that enhance soil physical properties and turfgrass growth.