Employing a Large-Scale Field Study to Assess Establishment of Native and Pollinator Seed Mixes for Solar Site Applications

Navigating the challenges of establishing vegetation on solar sites requires addressing diverse factors like pre-construction land use, soil preparation, and the effects of impervious panels on soil moisture. The lack of consistent regulatory oversight further complicates the process. However, many jurisdictions are prioritizing native vegetation and pollinator habitats, guided by "Pollinator Scorecards." Recognizing the complexity and extended timeline needed to establish these habitats, a comprehensive vegetation management plan and realistic timelines are crucial. Our ongoing three-year study at the Stantec Native Plant Nursery in Walkerton, Indiana, is comparing native and turf seed blends, seeding techniques, and soil amendments to enhance soil health and promote pollinator activity. This research, while focused on solar development, offers valuable insights for environmental restoration in various construction markets, including highways, landfills, and mining.

Full Abstract: Establishing vegetation on solar sites offers a variety of unique challenges including variability in pre-construction land use, project sequencing, agronomic potential of soils or substrates, soil preparation, in addition to shaded areas, panel drip lines and variable soil moisture regimes caused by overlying impervious panels. Moreover, consistent regulatory oversight and specific requirements for erosion/sediment control, stormwater management, and vegetative establishment are lacking in this rapidly expanding market.
Native vegetation, with the inclusion of flowering forbs for increased pollinator habitat, is a key focus in many jurisdictions. Several regulatory entities have developed “Pollinator Scorecards” to offer guidelines to promote a healthy vegetative stand that is attractive to pollinators throughout the growing season. While few will argue the benefits of increased pollinator habitat, establishing native and pollinator blends is often a more complicated and longer process than rapidly establishing turfgrass. Therefore, to achieve the minimum required cover, realistic timelines must be established, and comprehensive vegetation management plans must be considered to attain Notices of Termination (NOT).
Research plots were installed in October of 2021 at the Cardno/Stantec Native Plant Nursery in Walkerton, Indiana. The focus of this three-year study is to compare the establishment of a native seed blend and a native/turf seed blend at two seeding rates, employing both hydraulic or drill seeding techniques while also evaluating an Engineered Soil Amendment (ESA) to rejuvenate the depleted soil. One key aspect of the study is to validate or disprove the common perception that seeding rates must be doubled when employing hydraulic seeding methods versus drill seeding. The ESA used was hydraulically applied to provide both soil development and erosion protection.
Data collection throughout the 2022-24 growing seasons will include climatic records, maintenance activities, vegetative cover and density, stand height, and species diversity as well as qualitative observations of pollinating insects activity. Each plot will be photographed to record overall progress. Follow-up soil tests will be completed annually to monitor potential changes in soil development and health. While this study is designed with a focus on solar development, it has broader implications for utilization of native and pollinator species for environmental restoration activities in other construction markets such as highways, landfills, and mining.