Drs. Susan Day and Nina Bassuk have collaborated on a variety of research projects in the urban forest, with a special focus on soil remediation. Susan Day is an associate professor in the Virginia Tech Departments of Forest Resources & Environmental Conservation and Horticulture, and longtime Council stalwart Nina Bassuk directs the Urban Horticulture Institute at Cornell.
Here, Susan Day summarizes her findings after ten years of researching Soil Profile Rebuilding (SPR), a technique that the urban forestry community will be hearing about! See also this post from 2014 about Nina Bassuk’s related soil amendment research.
Soil Profile Rebuilding: An Alternative to Soil Replacement
by Susan Downing Day
Urban foresters and their allies know poor soils can lead to an endless cycle of dieback and tree replacement. Even if trees do establish, growth can be underwhelming and tree health disappointing. Increasingly, project managers have been turning to soil replacement, where existing soils are excavated and removed and replaced with “recycled” or blended soils. These soils present their own challenges, however. For example, many imported blends rely on high sand contents to improve drainage, resulting in low water-holding capacity and drought stress for unirrigated plantings. Resulting sharp transitions in soil texture introduce the possibility of creating a “bath tub” effect in situations where it is impossible to replace all the soil and new soils are confined to the immediate vicinity of individual trees.
There is an alternative to soil replacement that is especially appropriate where there are extended open soil (unpaved) areas such as in street medians—soil rehabilitation. Soil rehabilitation can help restore important ecosystem functions such as stormwater transmission and vegetation support to existing native soils.