Assessing Stormwater Infiltration Remediation Approaches for Developed, Compacted Soils.

Soils are generally compacted during land development through soil excavation and heavy equipment traffic. Compacted soils have limited infiltration and are susceptible to erosion.  Soil infiltration can be enhanced by various methods including tillage and compost addition. The objectives of this study were to determine the impacts of tillage with and without compost amendment on infiltration and runoff over time, and to determine the influence of mower traffic on these treatments.  A field study was conducted in the Piedmont of North Carolina in a split plot design with three blocks and treatments assigned randomly within each block. The three main treatments were: compacted soil, compacted soil with deep tillage (30cm), and compacted soil with deep tillage + compost. Each main plot was divided in half with conventional riding mower traffic on one half and no traffic and cutting with a string trimmer on the other. Runoff volume, turbidity, erosion and flow rate were measured for 17 storms after plot establishment. Infiltration rates were determined using a Cornell Sprinkle Infiltrometer. The cumulative amount of runoff volume for 13 storms in control plots was significantly reduced by both tillage alone and tillage with compost, with no difference between the two. The remaining four storms had no runoff from the tilled plots. The last storm where runoff was measured had over 89 mm of rain, and nearly 100% ran off the compacted plots compared to about 25% for tilled plots.  Sediment loss was highest in compacted plots and lowest in deep till, and mower traffic significantly reduced erosion. For the main treatments, the infiltration rates were significantly different and were in the order tillage+compost > tillage > compacted, and mower traffic had no effect.