Evaluation of an Urban Soil Rehabilitation Technique Incorporating Compost into Subsoil in Arlington County, Virginia

Summary

Soil profile rebuilding (SPR) is a soil improvement technique shown to increase tree canopy and soil carbon stores when compared to typical soil preparation practices in controlled plot experiments. The technique is intended for use in locations of extreme soil disturbance or compaction, such as near new building construction, road medians and planting strips. The potential benefits of SPR include reduced soil compaction, increased root growth and accumulation of soil carbon, increased tree growth rates, and improved soil drainage. So far the treatment has been evaluated in plot experiments in Blacksburg, Virginia, where the surface was maintained as bare soil via herbicide treatment in order to isolate the effect of SPR on soil carbon stores. In these plot experiments, however, saturated hydraulic conductivity is restricted by surface soil, likely due to the lack of typical landscape soil surface treatments. An SPR installation was installed in October 2012 in Arlington, Virginia, in new sidewalk cutouts to allow the evaluation of the treatment in its intended environment, and with typical mulch and turfgrass surface covers. We hypothesize that the treated plots will have lower bulk density, higher in filtration rates, more soil organic carbon and more microbial biomass carbon than control plots, in both surface and subsoil. We also hypothesize that treated plots will have moderated soil temperature extremes due to lowered bulk density and higher water holding capacities. A companion study will examine the effect of mulch type on the ability of a landscape to mitigate storm-water runoff. First-year data will be presented.