Parish Farm Water Quality Monitoring Project
Parish Farm is a 240-acre farm in Grundy County owned by the Iowa Academy of Science. The farm is managed as a "model farm" based on the following goals:
"To practice total environmental management and operation in order to demonstrate the most modern agricultural practices along with other conservation practices for establishing wildlife habitats, grass areas, and woods; to provide a quality environment for people; and to provide for an optimum yearly income."
One of the goals at the farm was to reduce the impact of agricultural chemicals on the surface water and groundwater systems. Fertilizer rates were set on a field basis related to crop type and crop-yield goals. The late-spring nitrate test developed by Iowa State University was used to determine fertilizer rates for the farm. Herbicide usage was based on a knowledge of the previous year's weed pressure. Insecticides were only used if crop scouting indicated a need.
Because of the practices initiated at the farm, it was an ideal setting to assess the effects of these practices on water quality at the farm. From 1988 through 1991, the Geological Survey Bureau monitored water quality using a network of monitoring wells, tile lines, and a small creek that runs through the farm.
Nitrate-N concentrations in monitoring wells varied with location, with mean concentrations ranging from 0.4 to 52.0 mg/L. Monitoring areas in non-cropped areas such as the prairie and wildlife area had lower mean concentrations than those from row crop areas. Nitrate-N from the tile lines ranged from 4.2 to 56.4 mg/L and reflect a mix of shallow groundwater quality and local runoff water. Climatic variation complicates the relationship between cropping practices and water quality and may have been responsible for some of the high concentrations of nitrate-N seen during the study. Seven pesticides were detected in samples from the farm and all had been used or were in active use at the farm. Atrazine was the most commonly detected pesticide: 81% of the surface-water samples, 43% of the tile-line samples, and 42% of the monitoring-well samples contained atrazine. Metolachlor was detected in 11% of the total samples and alachlor in 7% of the samples.
Monitoring water quality at a "real-world" site such as Parish Farm affords few unequivocal observations regarding water quality to crop practices. Even with the improvements in management practices, high nitrate-N concentrations and herbicide detections occur. This illustrates the inefficiencies inherent in intensive row crop production and the strong control exerted by climatic conditions. Nitrate monitoring is continuing at the farm to assess the long-term trends in water quality
For results on the on-going monitoring contact Lynette Seigley (Lynette.Seigley@dnr.iowa.gov) at (319)335-1575.
References:
B.K. Nations and G.R. Hallberg, Water Quality Monitoring from 1988 to 1991 at the Iowa Academy of Science's Parish Farm, Grundy County, Iowa. Journal of the Iowa Academy of Science, in press (Abstract).