BALTIMORE, Md., March 13, 2015—Excess fertilizer and manure applied to the Chesapeake Bay’s Eastern Shore are causing poor water-quality in streams that flow into the Bay, according to a new publication by the U.S. Geological Survey.
The report, a compilation and interpretation of research and data focusing on the Chesapeake Bay’s Eastern Shore, found that it receives nearly twice as much nitrogen and phosphorus per square mile of land area as other parts of the Bay watershed. The disproportionately large amounts of nutrients are due primarily to agricultural production of crops and livestock. More than 90 percent of nitrogen and phosphorus reaching the land in the Eastern Shore is applied as inorganic fertilizers, manure or comes from crops which use nitrogen from the atmosphere (see pie chart below).
The Bay and its tributaries have been degraded in recent decades by excessive nutrients, mostly nitrogen and phosphorus. An overabundance of nutrients deplete the Bay of oxygen needed for fish, crabs, and oysters, and, along with sediment, cloud the waters, disturbing the habitat of underwater plants crucial for aquatic life and waterfowl.
“On the Eastern Shore, the concentrations of nitrogen in groundwater, and nitrogen and phosphorus in surface waters, are well above natural levels and are among the highest in the nation,” said Scott Ator, a USGS hydrologist and co-author of the study. “We are also seeing worsening nitrogen and phosphorus concentrations in the Choptank River, which is the largest river on the Eastern Shore, despite management practices to improve water quality.”
The fertilizer and manure applied to agricultural lands in past decades exceed the amount needed by crops. Excess nitrogen accumulates in groundwater, and excess phosphorus in soils. Once in the groundwater and soils, the nitrogen and phosphorus move very slowly from upland areas to streams that eventually contribute to the water-quality problems in the Chesapeake Bay. Both the excess amount of nutrients applied to agricultural lands, and their slow movement, are delaying the full benefits of practices to improve water quality.
“The disproportionately large nitrogen and phosphorus yields from the Eastern Shore to the Chesapeake Bay are attributable primarily to agricultural activities but are also influenced by natural hydrogeologic and soil conditions,” said Judith Denver, a USGS hydrologist and co-author of the study. “The findings from the report will help inform more strategic placement of management practices intended to better utilize crop nutrients and reduce the excess available for transport to groundwater and streams.”
Home to more than 3,700 different species of plants and animals, the Bay is more than 186 miles from its headwaters in northern Maryland to its mouth in southern Virginia, and has a surface area of approximately 4,247 square miles. Chesapeake Bay is the largest estuary in the United States and a vital ecological and economic resource.
The Eastern Shore includes the area of the Chesapeake Bay watershed east of the Bay on the Delmarva Peninsula. It includes the Maryland counties of Caroline, Cecil, Dorchester, Kent, Queen Anne’s, Somerset, Talbot, Wicomico and Worcester. It also includes portions of all three Delaware counties and the two Virginia counties of Accomack and Northampton.
The federal government is working with all the states in the watershed and the District of Columbia to reduce nutrients and sediments through the Chesapeake Total Maximum Daily Load (TMDL), which was released in 2010. On the Eastern Shore and across the Bay watershed, the jurisdictions are carrying out Watershed Implementation Plans designed to comply with the nutrient and sediment reduction goals in the TMDL. Historic levels of funding from the federal government and other sources have helped agricultural producers implement practices to reduce the amount of nutrients leaching into groundwater and running off into surface waters.
The report is part of the USGS effort to provide science to help inform restoration and conservation of the Chesapeake Bay ecosystem. A major focus of the USGS effort is working with partners to explain nutrient and sediment trends in the Bay watershed.
“Understanding Nutrients in the Chesapeake Bay Watershed and Implications for Management and Restoration – The Eastern Shore,” by S.W. Ator and J. M. Denver, USGS Circular 1406 is available online.
For more information on the USGS Chesapeake Bay activities please visit the website.