Rain gardens, perennial plantings in shallow, manmade depressions large or small designed to catch and use rainwater runoff, are becoming increasingly popular among homeowners and cities.
In several communities, the U.S. Department of Agriculture (USDA) scientists are working on ways to improve rain gardens to reduce runoff and filter out pollutants from rainwater. Rain gardens are usually planted with a combination of native and non-native flowers, grasses, trees, and shrubs.
A research team comprised of a plant physiologist, a research associate, a soil chemist and their colleagues, all part of the Agricultural Research Service (ARS), is working in several locations on improving rain gardens. The ARS is the USDA’s main intramural scientific research agency; its research supports the USDA’s commitment to agricultural sustainability.
At the ARS Appalachian Farming Systems Research Center at Beaver, West Virginia, the team is working on replacement, or constructed subsoils and topsoils for use in rain gardens. The scientists are also working in cooperation with the National Turfgrass Research Initiative, Inc., a turfgrass industry/ARS program developed in 2007. Turfgrass experts’ top priority is improved degraded soils that include rural, urban, and industrial byproducts that can be combined with local soils.
In New Orleans, Louisiana, part of the ARS team is working at the ARS Southern Regional Research Center (SRRC). Scientists at the SRRC have found that poultry litter, a mix of droppings and bedding material such as sawdust and wood shavings, is the best organic component in constructed soils so far. The litter is composted in a special digester to remove odors and harmful microbes and stabilize the mixture.
Poultry litter biochar-activated carbons formed from the charred remains of poultry litter create a powerful magnet that can attract heavy metals including copper, cadmium, and zinc which are commonly difficult extract from wastewater. The team of scientists is testing the poultry litter biochar along with other farm and industrial byproducts in two rain gardens in Beaver and Beckley, West Virginia and at plots at a county landfill and a mining reclamation site.
In Marin County, California, the 10,000 Rain Gardens Project has been working over the past year to focus on making rainwater harvesting common practice among local homeowners. The project offers public education and how-to-workshops as well as tours of local rainwater harvesting projects. It has also established five permanent public demonstration projects throughout the county.
These include rain gardens and aboveground cisterns. There is an emphasis on the benefits of rainwater harvesting, including water conservation, mitigation of localized flooding and erosion, resolving building foundation moisture problems, and filtering run-off pollutants including gas, oil, pesticides, and fertilizers.
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