ARS researchers discovered a species of one-celled green algae that helps break down soil-applied herbicides and could lead to improved soil and water quality. The researchers are looking at microbial populations in three Mississippi watershed lakes—Beasley, Deep Hollow and Thighman—as part of the USDA-ARS Mississippi Delta Management Systems Evaluation Area (MSEA) project. They are evaluating farming practices in the 7,320-acre area surrounding the lakes. ARS studies indicate that farm management practices influence lake microbial populations and their impact on water quality. Deep Hollow watershed, where intensive conservation practices such as winter cover crops and reduced tillage are employed, had the lowest sediment and highest algal populations. These algae, Selenastrum and Ankistrodesmus, can absorb and break down herbicides such as atrazine and fluometuron, commonly used in corn and cotton production. ARS scientists also found that a specific group of bacteria, called fluorescent pseudomonads, can degrade metolachlor, propanil and trifluralin—three commonly used herbicides in the MSEA area. These bacteria and algae can reduce herbicide longevity in Mississippi Delta lakes.

Southern Weed Science Research Unit, Stoneville, MS
Robert M. Zablotowicz,601-686-5260, bzabloto@ag.gov

Using stream gauges, computers and other instruments, ARS researchers are monitoring the environmental impact of grass-based systems for managing dairy cows. Their work is part of the American Farmland Trust’s Cove Mountain Farm Project, begun last year on a 300-acre commercial dairy in Pennsylvania. Popularized abroad, the approach calls for grazing cows on carefully managed pastures of grasses and legumes like clover. In the United States, large dairy herds are generally confined to indoor feed regimens. But on small- to-medium sized dairies, grazing cattle on pasture can cut operating costs associated with growing, harvesting and storing crops like corn as year-round feed. Another benefit is the savings on housing and waste management costs. Unknown, however, is the extent to which nutrients from the waste of grazing cows contribute to nitrate leaching and phosphorus runoff. Both can diminish water quality. To assess this risk, scientists installed a network of piping beneath 10 acres of Cove Mountain pasture where the farm’s herd regularly grazes. Groundwater captured by the piping is sampled and analyzed. This information tells scientists where, when and how grazing may contribute to leaching. Elsewhere, stream gauges check for phosphorus runoff from pasture. Chambers that collect carbon dioxide, meanwhile, help scientists monitor the health and productivity of pasture plants. The findings could usher in new ways for farmers to manage pasture, meet their herd’s nutritional needs, and save money.

Pasture Systems and Watershed Management Research Laboratory, University Park, PA
William Stout, (814) 863-0947, ws1@psu.edu