Evaluation of a Soil Decompaction and Amendment Process for Urban Trees

Abstract

Researchers investigated the effects of a soil decompaction and amendment process (AFM) and its individual components (air tillage, fertilizer, and mulch) on soil properties at four urban sites: Anderson, South Carolina; Boston, Massachusetts; Myrtle Beach, South Carolina; and Pittsburgh, Pennsylvania, U.S. At each site, 50 red maples (Acer rubrum) were growing on compacted and/or nutrient-poor soils whose pretreatment bulk densities ranged from 1.14 to 1.74 g/cm3. Treatments were applied in the autumn and winter of 2005–2006, and measurements were taken through the end of 2008. The AFM treatment significantly reduced soil strength relative to control at all sites in 2006. There were significant treatment × location interactions in all years, with higher bulk density sites (Anderson and Myrtle Beach) showing the greatest magnitude and duration of response. The AFM and mulch treatments generally increased soil organic matter content, while air tillage alone significantly lowered soil organic matter content in Pittsburgh. At most sites, the AFM treatment was more effective than surface fertilizer application at improving soil fertility. AFM and mulched plots had significantly higher soil water content than other plots during periods of summer drought. Overall, AFM was effective in improving soils beneath established trees, and mulching was the most beneficial of the individual treatments.