Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 6, 1997
Publication Date: February 15, 1998
Citation: Stone, K.C., Hunt, P.G., Johnson, M.H., Coffey, S.W. 1998. GLEAMS simulation of groundwater nitrate-N from row crop and swine wastewater spray fields in the eastern Coastal Plain. Transactions of the American Society of Agricultural Engineers. 41(1):51-57. Interpretive Summary: In 1989, President George Bush signed into law the President's Initiative on Water Quality, which was intended to improve the quality of water in streams and ground water near farms and ranches. One project in this initiative is located in Duplin County, NC, on the Herrings Marsh Run watershed. There, scientists are trying to find ways to reduce the amounts of fertilizer and pesticides that leak into streams and ground water. While farmers change from traditional to more environmentally friendly methods, scientists are monitoring ground water on several farms in the watershed. Scientists installed monitoring wells in and around farmers' fields to evaluate the ground water quality. Most of the farms have good ground water quality. Fields in a few farms have ground water that occasionally does not meet drinking water standards. The farms with the worst water quality lie near several hog and poultry farms. It appears that one farm with poor water quality is improving its ground water quality. The ground water changes occur slowly so scientists use computer models to help predict how well the more environmentally friendly methods will improve ground water quality. The computer model predicts that current trends for this field will continue to improve water quality for the next few years.
Technical Abstract: Nonpoint pollution of surface and ground water resulting from agricultural management practices is a major water quality problem. This problem has been addressed since 1990 by a joint project among state and federal agencies on a demonstration watershed in the Cape Fear River Basin of North Carolina. Ground water in a typical row crop field and an atypical swine waste spray field was monitored. Ground water nitrate-N and ammonium-N concentrations for the row crop field averaged 13 and 0.2 mg/L, respectively, in a corn/wheat/soybean row crop rotation. Nitrate-N and ammonium-N concentrations in ground water at the atypical (overloaded) swine waste spray field had exceeded 80 and 16 mg/L in the spray field. Reducing the application rates and expanding this spray field have reduced the nitrate-N concentrations in this field. The monitored fields were simulated with the GLEAMS model. The model was evaluated for both row crop culture and for animal waste applications of nutrients. Model comparison and validation with ground water observations were performed. The model was also used to simulate the long-term impact and recovery of the overloaded waste spray field.