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LeMasters, Gary S.; Doyle, Douglas J. / Grade A dairy farm well water quality survey
[DNR-058] (1989)

Introduction,   pp. 1-2 PDF (660.9 KB)

Page 1

In 1985 Wisconsin farmers were reported to have used about 5.2 million
pounds of atrazine (a herbicide used primarily to control broadleaf weeds in
corn) and 3.4 million pounds of alachlor (Lasso*, a herbicide used primarily for
grass control in corn) on about 5 million acres of corn (WDATCP, 1986). At
about this time the Wisconsin Department of Agriculture, Trade and Consumer
Protection (WDATCP) began a monitoring program to determine if agricultural
chemicals were reaching groundwater in significant concentrations. Shallow
wells were installed at the water table immediately downgradient from
agricultural fields that featured sandy soils, shallow depth to groundwater, and
irrigation. Among the most frequently found compounds in this program were
atrazine and alachlor. At this time Wisconsin had not adopted any official
groundwater standards for these compounds and the unofficial guideline
concentrations were not being exceeded.
In 1988 the Wisconsin Department of Natural Resources (WDNR) adopted
health-based groundwater standards for atrazine and alachlor which were
significantly lower than the unofficial guidelines. While the monitoring
program showed that these compounds could reach groundwater at levels above
these new standards in susceptible areas, no reliable information was available
about the statewide extent of groundwater contamination from these
compounds. The Grade A Dairy Farm Well Water Quality Survey reported
herein was designed to meet this need.
The survey was funded with pesticide research fund monies collected by the
Agricultural Resource Management (ARM) Division of WDATCP, and by a grant
from the WDNR. All samples were collected between August, 1988 and
February, 1989. A total of 534 wells on Grade A dairy farms were sampled.
Throughout the report the concentration of a pesticide is expressed in units
of micrograms of active ingredient per liter of water, abbreviated ug/l. This is
the preferred unit for expressing a concentration of a pesticide in water, and is
equivalent to the more familiar unit of parts per billion, abbreviated ppb. The
concentration of nitrate + nitrite as nitrogen is expressed in units of milligrams
of nitrate + nitrite as nitrogen per liter of water, abbreviated mg/l, which is
the equivalent to parts per million. Nitrite concentrations in groundwater are
usually insignificant so throughout the report the abbreviation N03-N will be
used to denote both the nitrate and nitrite forms of nitrogen.

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