Runoff Quantity and Quality from Amended Urban Residential Lawns

Abstract

New residential landscapes in Florida are often installed on sandy fill soil that has been compacted (bulk densities >1.60 g/cm3) during the home construction process. The goal of this study was to determine whether incorporating compost into new residential lawns could reduce stormwater runoff volumes and nutrient loadings. Before landscape installation, one of three treatments (null, tilled, and tilled with compost) were applied to the lawn area (60% of landscape) and after landscape installation was completed, approximately half of the lots were topdressed. Overall, drainage areas with compost-amended soils produced 2.5% less runoff than tilled soils, but did not produce less runoff than null soils. However, considering variability across storm events, amending soils resulted in lower event runoff depths compared with tilled and null treatments, with effective curve numbers of 77, 88, and 82, respectively. Neither total nitrogen (TN) nor total phosphorus (TP) concentrations or loadings were significantly different based on treatment or topdressing. Annualized TN loading rates were highest for tilled soils (5.14 kg N/ha/year) and lowest for composted soils (4.21 kg N/ha/year). Tilled soils produced the greatest annualized phosphorus loading rates (1.18 kg P/ha/year), with null soils producing the lowest loading rates (0.73 kg P/ha/year). Results of this study indicate that amending compacted fill soils with compost prior to landscape installation decreased runoff volumes without increasing nutrient concentrations.