Water Quality Monitoring (1988 to 1991) At The Iowa Academy of Science\u27s Parish Farm, Grundy County, Iowa

In May 1988 sampling was initiated to evaluate water quality in relation to management practices at Parish Farm, which is owned by Iowa Academy of Science. Initial results showed tile-line effluent to have high concentrations of nitrate-nitrogen (N03-N). Twelve monitoring wells were installed over a one year period to analyze shallow groundwater at the farm. The wells, tile lines, and surface water were sampled monthly, through October, 1991, and the water analyzed for N03-N and some pesticides. N03-N concentrations varied, related to landuse and management of adjacent areas. Greater N03-N concentrations were detected from row-cropped areas than in the restored wildlife-vegetation buffer strip and prairie areas. The greatest concentrations (up to 79 mg/L) were associated with greater amounts of fertilized corn in the cropping sequence. Concentrations of pesticides were dependent on various factors such as chemical properties, season, hydrologic events, and patterns of use. Atrazine was the pesticide most often detected and was present in 46% of the samples. Seven agricultural pesticides used on the farm were detected in water samples with a maximum detected concentration of 6.9 μ/gL (for alachlor). Pesticide and high N03-N concentrations were detected in wells beneath the restored natural vegetation buffer areas, probably as a result of groundwater transport from application areas upgradient. The data suggest that the buffer strips were not effective at removing N03-N or pesticides from the groundwater flowing through these areas. N03-N concentrations were high (often over 25 μg/L) during the study, in spite of improved N management on the farm. The high concentrations may be related to mobilization of excess residual N03-N that accumulated during the dry years prior to the monitoring