Roadside improvement

This research summary is part of the final deliverable for Report 2025-22, "Comparison of Compost and Proprietary Soil Amendments for Vegetation Establishment," Published in March 2025.

Post-construction roadside soils often suffer from compaction, low fertility, and poor structure, challenging vegetation establishment and stormwater management. This study evaluates the effectiveness of organic amendments (OAs) and proprietary amendments as alternatives to traditional methods. The study involves greenhouse experiments (pot and mesocosm) and field experiments to evaluate vegetation growth and water quality across different amendment and soil applications. Results show that compost amendments significantly improve vegetation growth, with yard-waste compost outperforming others. Biochar shows early growth potential but requires nutrient supplementation for sustained performance. Proprietary amendments support rapid vegetation establishment, enhanced root density, and reduced nutrient leaching, with Sustane 4-6-4 exhibiting consistent growth across application rates. The field study validates greenhouse findings and shows increased biomass and root density with compost amendments, while proprietary amendments result in high nutrient retention and runoff quality. This study highlights the potential use of OAs and PAs to reduce erosion and support long-term vegetation growth. The findings provide practical guidelines, benefits and implementation steps for managing roadside soils after construction activities.

This report fulfills the requirements laid out in Sec. 160.2325 MN Statutes. The goal of the Highways for Habitat Program is to enhance Minnesota roadsides with vegetative buffers and pollinator and other wildlife habitat. This is the first year of this report. More information is available on MnDOT’s Integrated Roadside Vegetation Management webpage.

This photograph shows the plaque on the mill stone historic marker at Marine on St. Croix Roadside Parking Area.

This photograph shows the mill stone historical marker at Marine on St. Croix Roadside Parking Area.

This photograph shows the mill stone historical marker at Marine on St. Croix Roadside Parking Area from an angle.

This photograph shows the flagpole at Marine on St. Croix Roadside Parking Area.

This photograph shows the south side of the Marine on St. Croix bell historical marker.

This photograph shows the plaque on the bell historic marker at Marine on St. Croix Roadside Parking Area.

This photograph shows the gravel parking area at Marine on St. Croix Roadside Parking Area.