Best Practices
For nearly two decades, researchers at the University of Maryland Eastern Shore (UMES) have been partnering with scientists from the U.S. Department of Agriculture’s Agricultural Research Service to determine best practices for reducing nutrient pollution that’s already in the soil. They have worked to intercept it before it reaches rivers, streams, and groundwater in this low-lying region of the state.
The UMES campus, located on Maryland’s lower Eastern Shore, contains land along the Manokin River where a poultry business once operated. The soil here is rich in phosphorus and nitrogen from application of poultry litter over the years, making it an excellent location for graduate students and scientists to monitor the effectiveness of pollution-reduction practices in soils. (Soil is defined as the area between the surface, where rain falls, and the layer of dirt below the soil that is saturated with water—the water table and unconfined aquifer.)
UMES Associate Research Professor Amy Collick is working with her UMES colleague, Professor Arthur Allen, and Ray Bryant of the UDSA’s Agricultural Research Service. They have installed monitoring wells around the site of the former poultry operation to measure groundwater and the effectiveness of different experimental land-management practices. On their research and teaching farm, they are testing different practices to reduce soil-based nitrogen and phosphorus from leaching down to the aquifer or into the river. If a particular pollution reduction method succeeds, UMES researchers will assist willing local farmers to adopt the practice on their own properties. Researchers will monitor those farms for up to five years to gauge the efficacy of the method over time.
Below is a sampling of practices that Collick, Allen, Bryant, and their colleagues are testing:
FORESTED BUFFERS
Where to put them
Between an agricultural field and a surface water source
How they work
Plant roots absorb water running off the surface before it gets to the waterway or river; more nutrients taken up by plants means fewer nutrients reach the water.
Where they are
Farmers throughout the Coastal Bays and Chesapeake Bay watersheds have been planting forested buffers, often with federal assistance, for decades.
Effectiveness
Reductions of 30 to 50 percent for phosphorus, and about 50 percent for nitrates on the UMES research site.*
*Collick noted that land slope at the research site may also contribute to nutrient reduction, beyond what plants remove, accounting for higher reductions than seen elsewhere in Maryland.
BIOREACTORS
Where to put them
At the edge of an agricultural field
How they work
A bioreactor is a buried trench with a carbon source—usually wood chips or sawdust mixed with soil at an equal ratio—that intercepts nitrogen-rich groundwater and converts its nitrogen into nitrogen gas. This process, called denitrification, prevents the nitrogen from flowing into a stream. At the UMES farm, Collick said, the trench is dug about five feet deep, parallel to the river, on the site of the former poultry operation. That positioning helps determine its effectiveness at keeping runoff out of a stream on a farm.
Where they are
Approved as a conservation practice in 2015, they are more common in Iowa and South Dakota; however, bioreactors are starting to get some traction on the Eastern Shore, with local contractors helping farmers secure funds to install them.
Effectiveness
An expert panel convened by the Chesapeake Bay Program conservatively estimated that bioreactors remove 20 percent of total nitrogen in water from the area they treat; UMES research is achieving closer to 35 percent. Collick said the forested buffer and the bioreactor together make a powerful combination for pollution reductions.
GYPSUM CURTAINS
Where to put them
Across a drainage area
How they work
U.S. Department of Agriculture (USDA) research has shown that 90 percent of dissolved phosphorus entering farm drainage ditches comes from groundwater, not surface runoff. The “curtains” are actually gypsum dust that is applied to the sides of a drainage ditch. It forms a curtain-like barrier between the soil on either side of a ditch. This nutrient reduction practice removes dissolved phosphorous. It works because soluble calcium in gypsum chemically joins with the phosphorus and forms calcium phosphate precipitate, which remains in the curtain and doesn’t enter the ditch water. Once installed, they resemble drapes on a window, which is how they got their name.
Where they are
Mostly on the UMES research farm, although a few Somerset County farmers are experimenting with them, and the power industry has run some pilot projects with Ohio farmers.
Effectiveness
UMES work and UDSA research have shown that the gypsum reduces soluble phosphorus by 75 to 90 percent. But animals, such as muskrats, can disrupt the curtains when they burrow into the ditches, creating openings that diminish effectiveness.
Header photo: USDA-ARS soil scientist Ray Bryant (left) and Arthur Allen, a professor in the Department of Agriculture, Food and Resource Sciences at UMES, collect groundwater samples before and after they are filtered through a “curtain” of gypsum. Photo, Stephen Ausmus
Forest buffer photo: Courtesy of Ben Longstaff / IAN
Bioreactor graphic: Nicole Lehming / MDSG, redrawn from graphic by Louis A. Schipper / The University of Waikato
Gypsium curtain photo: Gypsum curtain installation at a private farm on the Eastern Shore. Photo, USDA/ARS
