Groundwater nitrate depletion in a swine lagoon effluent-irrigated pasture and adjacent riparian zone

A. J. Sloan; J.W. Gilliam; J.E. Parsons; R.L. Mikkelsen; R.C. Riley

ABSTRACT:

Irrigation of anaerobic swine lagoon effluent onto cattle-grazed grass pastures represents a common waste treatment method in the Coastal Plain of North Carolina. However, such treatment strategies can result in high nitrate (NO₃) concentrations in the shallow ground-water beneath spray fields, and ultimately surface waters receiving groundwater discharge if application rates exceed crop and animal removal. This study was conducted to determine NO₃ accumulation and movement in the spray fields and riparian zone on a swine farm in eastern North Carolina, as well as effects of effluent irrigation on streams recharged by shallow ground-water flow. Increases in the NO₃ concentration of receiving streams occurred over the farm, suggesting that some NO₃ was reaching surface waters. Despite evidence of denitrification losses in riparian areas, the riparian zone did not fully protect the receiving streams from high concentrations of NO₃ in the groundwater.

Footnotes

A.J. Sloan, J.W. Gilliam, and R.L. Mikkelsen are with the Soil Science Department, and J.E. Parsons is with the Biological and Agricultural Engineering Department, North Carolina State University. R. C. Riley is with the USDA Natural Resources Conservation Service (USDA-NRCS). This work was supported by the North Carolina Agricultural Research Service, Competitive Program of the National Research Initiative, and the USDA-NRCS. Appreciation is extended to Carroll's Farms for allowing access to their farm and other help.
Copyright 1999 by the Soil and Water Conservation Society

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