1 Maryland Department of Transportation State Highway Administration Sustainable Landscaping Practice For Enhancing Vegetation Establishment 1 Hua Xiang, Maryland DOT SHA PI: Dr. Stuart Schwartz, UNIV. OF MD, BALTIMORE CO. Landscaping-Practice-for-Vegetation-Establishment_Report.pdf

2 Maryland Department of Transportation State Highway Administration Compacted soils within highway medians and other roadside areas result in limited capacity to support healthy vegetation, stormwater infiltration, and tree growth.  The Maryland Department of Transportation explored alternative, sustainable practices to loosen compacted soil and improve soil structure. PROBLEM STATEMENT Maryland Improves Median Landscape And Drainage

3 Maryland Department of Transportation State Highway Administration THE PROJECT Demonstrated the effectiveness of innovative soil decompaction and amendment practices Compared with standard Maryland practices for turf establishment. Evaluated the effectiveness of forage radish as a means of "bio-drilling" to further loosen the compacted soil. Developed revised specifications for such practices. TO HELP TURF, MEADOW, FOREST AND LANDSCAPE PLANTINGS TO THRIVE

4 Maryland Department of Transportation State Highway Administration The Taneytown site was a heavily compacted old MD Route 853 roadbed identified for future afforestation. Replicate treatments with suburban subsoiling were compared to standard SHA turf establishment. The suburban subsoiling approach was the combination of deep soil ripping and compost amendment. Forage radish were planted as a measure of “bio ‐ drilling.” Experimental test plots were established in Taneytown, MD, to test suburban subsoiling and bio-drilling. RESEARCH PERFORMED

5 Maryland Department of Transportation State Highway Administration FORAGE RADISH How many people know what a forage radish looks like?

6 Maryland Department of Transportation State Highway Administration FORAGE RADISH

7 Maryland Department of Transportation State Highway Administration An example of Standard Turf Preparation: Rototill Seed Starter Fertilizer Mulch (Penimulch) Suburban Subsoiling tested: Complete Cultivation (next slide) Compost Amendment Seed Mulch EXPLANATION What is Suburban Subsoiling? 7

8 Maryland Department of Transportation State Highway Administration 8 COMPLETE CULTIVATION Adapted from open pit mine reclamation

9 Maryland Department of Transportation State Highway Administration 9

10 Maryland Department of Transportation State Highway Administration RESEARCH RESULTS Demonstrated significant improvements to the compacted soils, resulting in more successful turf establishment and dramatic increases in storm water infiltration.  Suburban subsoiling resulted in a permeable soil profile with higher organic matter  The soil infiltration rate is comparable to standard turf establishment practices.  The mature deer compost used provided stable soil carbon with nutrients and minimized the risk of nutrient losses or leaching.  The significant radish development on plots demonstrated the high potential of bio-drilling as a multi-year strategy to mitigate compaction.

11 Maryland Department of Transportation State Highway Administration The median soil strength (a surrogate for compaction) with depth for the two treatments was shown in below figure. A soil strength above 200 PSI is generally considered to be limiting and above 300 PSI restrictive for vegetation growth.

12 Maryland Department of Transportation State Highway Administration Figure 1 ‐ Test Plot in Taneytown, Maryland Maryland State Highway Administration High Value Research Project

13 Maryland Department of Transportation State Highway Administration IMPLEMENTATION  Cultivating deep permeable organic soil profiles by adapting these land development practices will result in reduced life-cycle costs for green asset maintenance (low-risk too!).  Application of forage radishes are suitable for existing meadows and other appropriate roadside landscape management areas.  SHA can include these techniques in the designer’s toolbox to promote long term landscape sustainability.

14 Maryland Department of Transportation State Highway Administration Project Contact: Sharon Hawkins Research Division Project Manager THANK YOU 14