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United States Department of Agriculture

Agricultural Research Service

Title: STREAM NITROGEN CHANGES IN AN EASTERN COASTAL PLAIN WATERSHED

Authors
item Stone, Kenneth
item Hunt, Patrick
item Novak, Jeffrey
item Johnson, Melvin
item Watts, Donald
item Humenik, Frank - NC STATE UNIV

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 3, 2003
Publication Date: April 12, 2004
Citation: Stone, K.C., Hunt, P.G., Novak, J.M., Johnson, M.H., Watts, D.W., Humenik, F.J. 2004. Stream nitrogen changes in an eastern coastal plain watershed. Journal of Soil and Water Conservation. 59(2):66-72.

Interpretive Summary: Nonpoint source (NPS) pollution occurs when nutrients from fertilizers and other sources wash from the fields into streams and rivers. This NPS pollution is a major concern throughout the USA and the world. To address the concerns about NPS pollution, a project was initiated in the coastal plain region of North Carolina to help farmers reduce nutrient losses from their farms and fields. The farmers were assisted in developing plans to effectively manage applied nutrients and in managing animal waste called Best Management Practices (BMPs). To determine the effectiveness of these BMPs in reducing nitrogen losses to the environment, researchers measured stream water nitrate and ammonia concentrations before and after the plans were implemented throughout the project area. The researchers found that nitrate concentrations were reduced up to 50% after the BMPs were implemented. The ammonia concentrations remained about the same after the BMPs were implemented. These overall project results indicated that the BMPs were effective in reducing nitrogen losses from the project area.

Technical Abstract: Agricultural nonpoint source pollution (NPS) is a major water quality concern throughout the USA and the world. Concerns over agricultural NPS are heightened where intensive agricultural operations exist near environmentally sensitive waters. To address these environmental concerns, a Water Quality Demonstration Project involving federal, state, and local agencies; private industry; and local landowners was initiated in 1990 on the Herrings Marsh Run (HMR) watershed in the Cape Fear River Basin in Duplin County, NC. Best Management Practices (BMPs) to reduce nutrient losses to the environment included nutrient and animal waste management plans, soil conservation practices, and an in-stream wetland (ISW). Stream nitrate-N and ammonia-N were measured at the watershed outlet and at three subwatersheds outlets from 1990-1998 to evaluate the effectiveness of the BMPs. The project was divided into pre-ISW (September 1990-May 1993) and post-ISW (June 1993-December 1998) time periods because the majority of the BMPs were implemented at the time of the ISW establishment. Post-ISW stream nitrate-N concentrations were significantly reduced on the HMR watershed (56%) and on each of the three subwatersheds (4% to 56%). The HMR watershed nitrate-N concentrations were reduced from 2.01 to 0.88 mg/L. One subwatershed had stream nitrate-N concentrations reduced from 5.63 to 2.74 mg/L. Nitrate-N mass export from the HMR watershed was significantly reduced on an annual basis from 7.14 to 3.88 kg/ha. Ammonia-N concentrations and mass export from the HMR watershed were unchanged from the pre- to post-ISW periods. The results of this study indicate that the implemented BMPs were effective in reducing nitrogen loss from the HMR watershed.

Last Modified: 9/1/2014