Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 21, 1997
Publication Date: N/A
Interpretive Summary: Nitrogen applied to cropland as part of normal fertilizer usage can contaminate ground water in the form of nitrate (NO3). Because nitrate is toxic, its presence in ground water is of public concern. This research investigated the role present and past cropping management has on nitrate leaching into a shallow aquifer (ground water) in Northern Missouri. Twenty-five percent of the wells were found to be contaminated with nitrates at levels greater than the 10 parts per million maximum contaminant level set by the U. S. Environmental Protection Agency. The results indicated that over-application of N as a nutrient for crops, whether from N fertilizer or animal manure applications, can result in elevated nitrates in ground water to levels that persist from years to decades. Current farming systems aimed at improving nitrogen use efficiency appear to be improving the ground water quality, but because of the aquifer's ability to store NO3, decreases in ground water NO3 concentratio are slow. Therefore, the significance of this research is that long-term overuse of N fertilizer and/or animal manure in association with corn production can negatively impact ground water quality for decades.
Technical Abstract: A major objective of the Management Systems Evaluation Areas (MSEA) Project has been to assess farming system impact on NO3-N concentrations in shallow aquifers. In Missouri our interest was to assess farming systems on the claypan soil/glacial aquifer. Three fields were selected and instrumented with ground water wells in the spring of 1991. Wells were sampled quarterly and analyzed for NO3-N. Average NO3-N concentration since 1991 was 7 mg L**-1, but 25% of the wells had NO3-N in excess of 10 mg L**-1. In one field, NO3 concentrations were much higher and are still decreasing after apparently receiving excess N from manure and N fertilizer before 1980. Long-term N management has long-term impacts on ground water quality in this aquifer. Current farming systems are probably affecting ground water quality but because of the glacial till's apparent buffer for NO3 storage, ground water NO3 concentration changes are slow.