Long-Term Remediation of Disturbed Urban Soils

Summary

Long Term Remediation of Disturbed Urban Soils

By Miles S. Sax & Nina L. Bassuk

Cornell University – Dep. Of Horticulture

Soils found in human-impacted landscapes exhibit biogeochemical processes that are distinct and unique compared to natural landscapes. As a result of urban development soil quality is typically diminished resulting in reduced ecosystem services and the failure of landscape plant establishment.  On the Cornell campus a long-term (12-year) study measured the impacts of a soil remediation strategy on soil quality indicators. The “Scoop & Dump” process of soil remediation consisted of physically fracturing of soils and incorporating large volumes of compost (30% by volume) with the use of a backhoe or mini excavator.  To replenish incorporated organic matter, mulch was added annually. The study found that over time remediated soils exhibited reduced bulk density (g/cm³), increased active carbon (g/kg), and an increase in potentially mineralizable nitrogen (µgN/ gdwsoil/week). In comparison to non-remediated soils, the study found improvements in aggregate stability (%), available water holding capacity, total organic matter (%), active carbon (g/kg), soil resistance (PSI) and a reduction in bulk density (g/cm³).  The application of this soil remediation strategy has been used to restore soils damaged by heavy equipment, building construction and other urban impacts.  It is significant that these improvements were maintained or enhanced over time.  A study of plant growth of remediated and unimproved soil will also be discussed.  Application of this process offers an alternative to using specified soils that are often mined and shipped long distances. This technique offers a practical, research-based tool for green industry professionals, arborists and landscape contractors and has a strong potential for improving soil quality using locally sourced materials and sustainable methods.