PLAINS – Solar farms are an increasingly popular way for landowners to power their communities. With an array of ground-mounted solar panels absorbing the sun’s energy, solar farmers are paid to send any unused electricity to the power grid for distribution.
As solar farms appear in the United States, researchers from the University of Georgia are working to improve biodiversity at solar sites as part of a larger multidisciplinary research program designed to support both the sustainable energy and ecosystem health.
Funded by the U.S. Department of Energy’s Office of Solar Energy Technology, the Photovoltaic Stormwater Management Research and Testing Project uses five existing solar sites in Georgia, New York, Colorado, in Oregon and Minnesota to study stormwater infiltration and runoff in solar farms.
A solar farm with more than 3,800 panels now sits on a seven-acre research site in Plains, where former President Jimmy Carter’s family grew peanuts and soybeans.
Carter was an early advocate for clean energy development across the United States, from the West Wing of the White House to pockets of rural America, like his hometown of Plains. The Plains solar site now feeds into Georgia Power’s grid, providing electricity to about half of the city’s residents, according to a Fresh Energy case study.
When solar farms are installed, it removes ecologically important habitat, especially for pollinators, said Bodie Pennisi, professor of horticulture at UGA and researcher on the project.
To study how to increase biodiversity in solar farms, UGA Cooperative Extension specialists and researchers from the College of Agricultural and Environmental Sciences are testing mixtures of wildflowers planted among the panels to measure establishment and success. habitat over several seasons.
They will also assess the impact of grass and wildflower mixtures on pollinator populations in an effort to restore pollinator habitat, a well-known priority of former First Lady Rosalynn Carter, who helped create the Rosalynn Carter Butterfly Trail.
Jason Schmidt, associate professor of entomology, said choosing plants to grow on the solar farm involved determining whether they would grow in southern Georgia, attract pollinators and natural enemies of common pests (beneficial insects) and leave. easily from seed. The researchers also made sure to select annuals and perennials that would bloom throughout the season.
The species chosen for the project were specifically bred for the potential to do well in hot, dry conditions on the farm, which is not irrigated.
“We also looked for varieties that would flower under the panels so that they weren’t in direct competition with the main purpose of the site, which is solar energy,” Schmidt said. “We wanted to bloom in peak season, so we chose species that would bloom at certain times, and then we combined all of those bloom times so that we always had something that bloomed throughout the season.”
The UGA team chose three different seed mixes for the flat, sandy site, including a grass mix with crabgrass, annual ryegrass and panicum, a low-diversity pollinator mix containing seven species, including Indian blanket flower, a common sensitive plant, butterfly milkweed, southern elephant’s foot, fringed blue star, rayless sunflower, and southern beard tongue; and a high-diversity pollinator mix of 18 species, including Indian blanket flower, pigeon pea, black-eyed susana, yarrow, lanceolate coreopsis, southern elephant’s foot, mist and 11 others.
While they’re still monitoring wildflower plots at the Carter Farm solar site to determine the full impact of pollinator-friendly seed mixes, Pennisi and Schmidt said only about 35% of the species planted became well established. on the site. Using existing research from other parts of the country, the researchers knew that many plant species — including those in the daisy family such as asters and blankets — were attractive to pollinators, primarily bees.
Josh Grant, an entomology PhD student working on the project, monitors insect populations using sweep nets and summarizes the results into functional groups, including pollinators, natural enemies, herbivores and decomposers. In the 2021 season, herbivores and decomposers made up more than 65% of the total arthropods captured, while pollinators were the least populated insect group in each plot.
“Our 12-inch maintenance mowing height likely hampered flower production and therefore reduced pollinator numbers,” Grant reported. The researchers expect the number of flowers – and therefore the number of pollinating insects observed – to increase this year as the perennials in the study reach their adult size.
Unfortunately, the researchers also encountered extreme pressure from native and exotic weeds.
“Even if native plant species are grown under ideal conditions from transplants, great care must be given to weed control,” Scmidt said. “What we will learn is what to plant and when to plant it in these new agrivoltaic environments.
“The weed pressure is relentless. That’s really the challenge anywhere, because the (weed) seed bank is very rich in the soil, and every time you turn the soil, it moves the seeds to the surface. This is a problem that happens over and over again, but if you mow often enough you hope to reduce the seed bank so that you don’t have any newly formed seeds. But it takes years and years to know if you’ve depleted the seed bank significantly.
UGA soil scientists will monitor the site to explore the relationship over time with soil moisture, temperature, and whether the soil microflora is enriched by the plantings.
The project was renewed for three years thanks to recent funding from the National Renewable Energies Laboratory, leader of the overall project.