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).
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