Tillage and Amendments to Remediate Compaction for Post Construction Soils.

Soils are compacted during urban land development through grading activities and heavy equipment traffic. Compacted soils have limited infiltration, difficult vegetation establishment, and are susceptible to erosion. Soil infiltration can be enhanced by various methods including tillage and addition of amendments. The objectives of this study were to determine the impacts of tillage with and without amendments on infiltration over time for simulated construction sites.  Plots were established at three locations, the Sandhills, Mountain, and Piedmont regions of North Carolina, to evaluate three main treatments: compacted soil (control), and compacted soil with both shallow (15 cm) and deep tillage (25-30 cm). Additional treatments at one or more sites included compost, cross-linked polyacrylamide (xPAM) and lime amendments. Sub-treatments included maintenance with and without mower traffic. Infiltration rates were determined using a Cornell Sprinkle Infiltrometer. The infiltration rate was significantly different between control and tillage treatments at the Sandhills site, and lime had no effect on infiltration.  Infiltration rates at the Mountain site on tilled plots were significantly higher than control plots and there were no differences between shallow (15 cm) and deep (25-30 cm) tilled plots.  Infiltration rates in plots with and without mower traffic were similar and xPAM had no effect. The results at the Piedmont site showed the same pattern as mountain site, and lime had no effect on infiltration. The large differences in infiltration between tilled and control plots were maintained up to 31 months, although infiltration tended to increase in the compacted plots.  The results suggest that tillage treatments can increase infiltration in soils compacted by construction activities and that this can be maintained for at least the 2-3 years we monitored. This can substantially reduce runoff from vegetated areas and possibly provide opportunities to manage runoff from adjacent impervious surfaces.