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Kansas Geological Survey, Current Research in Earth Sciences, Bulletin 238, part 1

Factors Affecting Nitrate Concentrations in Ground Water in Stafford County, Kansas

Margaret A. Townsend and David P. Young
Kansas Geological Survey


Nitrate contamination of the Great Bend Prairie aquifer in south-central Kansas is more pronounced at shallower than at deeper portions of the aquifer. Factors influencing the occurrence of nitrate in the shallow ground water include irrigation-well density, subsurface clay lenses, and land-use practices. Ground-water samples were taken from 42 wells, including deep (irrigation) wells and shallow (domestic and stock) wells. Except for one well with an anomalously high concentration due to a point source, nitrate-N concentrations of sampled wells ranged from 1.3 to 13.3 mg/L with a mean of 5.4 mg/L and a median of 4.7 mg/L. Statistical analyses indicate that shallow ground water is more susceptible to contamination than deeper ground water and that lower nitrate-N concentrations are probable in wells with a greater thickness of clay above the well screen. Irrigation-well density showed a statistically significant positive correlation with nitrate-N concentrations of shallow wells. No significant difference in nitrate-N concentrations was found to result from the two irrigation methods (flood versus center-pivot) used in the area. Nor were there significant differences in nitrate-N concentrations between sandy and loamy soils. Land-use practices and subsurface stratigraphy may be better indicators of potential nitrate contamination than the surface soils.

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Kansas Geological Survey
Placed online 1995