Pilot field study of structural soil materials in pavement profiles

The Urban Horticulture Institute at Cornell University (UHI) has been designing and testing sub-base materials that can be compacted with typical construction equipment, meet normal engineering expectations for materials under pavement, and encourage root growth. [UMN]

"A rhizotron pilot study was conducted to evaluate plant responses in a standard sidewalk installation in comparison to a test profile of skeletal soil material (SSM) and a field control. Chlorosis was detected in the standard sidewalk trees, whereas the SSM profile was comparable to the agricultural control. Roots were observed at the rhizotron wall in 1996. Root counts and distribution by depth suggested an increase in roots for Acer camprestre and Tilia cordata, with roots in the SSM profile occurring predominately in the lower regions of the pavement profile. Trees in the standard sidewalk profile were relegated to the shallow base course layer typical in northeastern sidewalk construction. Roots of Malus Adirondack followed the same pattern of rooting depth, but there were more roots observed in the standard sidewalk profile. Several parameters were investigated to account for the preferential root growth deeper into the SSM profile. After ascertaining the consistency with depth of moisture, density, and oxygen levels in the SSM profiles, it is suggested that temperature fluctuations may be a contributing factor for the root distribution phenomenon." [Abstract]

[San Francisco, Mar. 5-6, 1998]

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