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 groundwater 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 nitrogen (N) from manure and N fertilizer before 1980. Long-term N management has long-term impacts on groundwater quality in this [...]
