Amending constructed roadside and urban soils with large volume-based compost applications: effects on water quality

摘要

Mineral nutrients imported in composted dairy manure (CDM) and municipalbiosolid (CMB) amendments for highway-rights-of-way and urban landscapes can posea threat to surface water quality. Treatments were developed to evaluaterecommendations for amending roadside and urban soils with compost at large volumebasedrates. Texas Department of Transportation (TxDOT) recommendations wereevaluated in 2002 and 2003. Municipal recommendations were evaluated in 2004.Treatments were imposed on 4 by 1.5-m field plots on a constructed soil with an 8.5%slope. Three TxDOT compost application methods were tested; incorporation at 25% byvolume (CMT), topdressing over vegetation (GUC), and topdressing a 5-cm compostwoodchip mix over bare soil (ECC). In 2003, a 12.5% CMT treatment was substitutedfor the GUC, and two contrasting composts were compared. In 2002, soil testphosphorus (STP) concentrations (mg kg-1) were 291, 360, 410, and 1921 mg kg-1 in the0 to 5-cm layer of a course textured CMT, fine textured CMT, GUC, and ECCtreatments, respectively using CDM. In 2003, STP concentrations were 264, 439, 496,623, 1115, and 2203 mg kg-1, in the 0 to 5-cm layer after incorporation of CDM andCMB at the 12.5 and 25% volume-based rates, and topdressing the 5-cm CDM- orCMB-woodchip mix over bare soil, respectively. In 2004, contrasting CMB products,relatively low or high in total phosphorus (TP) were incorporated into the soil at 12.5and 25% by volume, or imported in transplanted sod at the 25% by volume rate. TheSTP concentrations were 87, 147, 180, 301, 322, and 544 mg kg-1, respective to thepreviously defined treatments. Runoff water from 14, 10, and 8 natural rain events wasused to characterize nutrient and sediment transport in 2002, 2003, and 2004,respectively. Concentration of TDP in runoff water was highly variable for roadsidetreatments across rain events. Mass losses of TDP were similar after CDM or CMBwere incorporated into the soil at 12.5 and 25% by volume. Compost incorporation wasthe most effective method for limiting TP loss in runoff. Roadway and urban soils areexpected to contribute greater TP losses as P concentration increases in soils.