Fate of nitrogen from agriculture in the southeastern Coastal Plain

ABSTRACT:

Nitrogen (N) contamination of surface and groundwater is a health concern for both humans and animals. Excess nitrogen in surface water bodies may contribute to eutrophication. Elevated nitrate (NO₃-N) concentrations in drinking water have caused infant death from the disease methemoglobinemia. Formation of potentially carcinogenic nitrosamines in the soil from nitrite (NO₂-N) and secondary amines is also a health concern. Both NO₃-N and NO₂-N have been shown to negatively affect the metabolism of domestic animals. Movement of NO₃-N and NO₂-N to groundwater is of particular concern in the southeastern Coastal Plain because of the unique climatic, soil morphology, and geohydrologic regimes of the region. Climatically, the southeastern Coastal Plain is characterized by warm temperatures and relatively high rainfall. Because of the extended growing season, multicropping, which requires multiple applications of nitrogen, is commonly practiced. Annual rainfall distribution often also requires use of supplemental irrigation. The combination of relatively high nitrogen inputs, high rainfall, and use of irrigation for crop production coupled with areas of permeable sandy-textured soils and geologic materials means that large portions of the coastal plain may have high potential for nitrogen contamination of surface and ground waters. Research at the Southeast Watershed Research Laboratory (SEWRL), USDA-ARS, in cooperation with the University of Georgia over the past 20 years has focused on determining factors affecting nitrogen transport and transport rates over a range of coastal plain soils and management scenarios. This paper examines the findings from these extensive studies, reports new findings from a long term study, and synthesizes all information to examine the long-term implications for nitrogen contamination of soil and water from agriculture in the southeastern Coastal Plain.