Using Ground Electromagnetic Conductivity to Determine the Source of Nitrate in Dairy Wells
Radcliffe, David E.
Brune, D. E.
Drommerhausen, D. J.
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recent study of dairies in a five-county area in north Georgia found a high incidence of nitrate nitrogen (NO3-N) contaminated well water. We used a ground electromagnetic (EM) conductivity meter to survey nine dairies in the region to determine the source of contamination. Ground EM conductivities were highest in the loafing areas on most dairies. These are the corrals or small fields near the barn where the milking herd is kept when it is not in the barn or on pasture, and other areas near the barn where there is high animal traffic. Conductivities were typically in the range 15 - 20 mS in -1 in these areas, compared to less than 10 mS ni l in the pastures away from barns. Water samples from groundwater observation wells installed in the loafing areas on three diaries had NO,-N concentrations of 47-135 mg/L compared to 12-16 mg/L from a well in a pasture. There was evidence of seepage at four of the seven wastewater lagoons we surveyed, but the loafing areas appeared to be a greater threat to drinking water supplies because they were closer to the milking barn where the supply well was located and because they affected a larger area than the lagoons. Best management practices need to be developed that address nitrate leaching from loafing areas.