The Serious Work of Designing and Building with Soil for New Landscapes.

All plant-based natural systems, whether or not they are human-made, rely on soil to thrive. Landscape architects are involved in the redesign and remediation of many of the complex contemporary construction projects involving waterfront and inland sites that have been industrialized, urbanized, abused, and contaminated and that often have none of the horticulturally viable soil essential to restoring the functioning natural systems of our built landscapes. Soil scientists are uniquely qualified to contribute to this work and yet this partnership is rarely forged. Why is that? Using case studies, this session will examine the myriad challenges that soil brings to every constructed landscape, while making an appeal for soil scientists to expand their study, research, and knowledge of soil used in construction projects, particularly the aftermath of urban soil conditions. At a 1985 meeting of the International Society of Arboriculture, Dr. Philip J. Craul presented compelling findings that urban soil is a unique anthropogenic condition that defies standard soil classification, has lost basic functionality, and fails at formation. While significant work by Dr. Craul and his contemporaries has elucidated this topic for designers like never before, there is still much to do in addressing the challenges of building with soil, of making landscapes from scratch. Soil scientists have an unprecedented opportunity to partner with landscape architects to provide much needed knowledge about soil design, re-use, procurement, verification, construction, and establishment, knowledge that would enable designed landscapes to fulfill the ambitious, but not unreasonable, expectation that they will endure for generations.

 

Landscape architects must rely on edapholological information from the NRCS to understand the chemical and physical relationships between soil and plants, despite the fact that the needs of and demands on horticultural soil are different from agricultural soil. The “crops” for each carry quite different expectations. Soil that is used for building must have specific characteristics that result in particular short- and long-term behavior and performance criteria for each ecosystem in a designed landscape. Soil physics, geotechnical properties, chemical makeup, hydrologic profile, as well as macro-micro-molecular processes are all considerations in the design of horticultural soil. In construction, the steps of harvesting, blending, trucking, placement, and establishment bring up questions about disaggregation, pore space loss, compaction, infiltration, biology, formation, stockpiling, erosion control, and equipment. The answers to these and many more practical questions are needed for creating soil management programs in landscape projects. There is serious work to be done; together soil scientists and landscape architects can make a difference in the quality and longevity of landscapes.