The Critical Aspects of Working with Urban Soils: A Landscape Architects Perspective.

Urban soils are dramatically different from natural soils.  The way they are described, modified and specified for incorporation into landscape projects to support plants requires that the soil scientist understand these differences.  Issues include: difficulty understanding existing soil conditions; the fact that the existing conditions at the time of the design and specifications will be substantially different from the conditions when the landscape contractor arrives at the site; problems with importing and mixing soils, the need for a redefinition of even basic soil concepts such as profiles and what constitutes organic matter; soil settlement after installation, sustainability of the overall soil systems; broad differences of opinion within the science of engineered soils and other methods to provide rooting soil under pavement; the reality of construction schedules and budgets; project needs from marketing and site design to civil engineering and architecture requirements often conflicting with what may seem like sound soil recommendations; and a general lack of knowledge of even rudimentary soil science on the part of most landscape architects.  These issues create a volatile chain of decisions that can result in extremely poor soil quality even in projects with the best of intentions. This presentation will discuss the most critical points that need to be balanced and how they interrelate when translated into construction plans and specifications. The session will propose that some of the important concepts originating from agricultural soil science need to be rethought when working with the design of urban soils.