Monitoring wells were established in-field along 2 rows, parallel to the irrigation
road (Figure 1). A 3-foot well screen was located just below the water table. The wells
were fitted with below-ground couplings so that they could be disconnected at a depth of
18" below the soil surface and tillage operations could proceed normally. When
disconnected, wells were capped and iron plates were placed over the wells so they could
be located with a ground penetrating radar unit. Once tillage was complete, the above
ground sections of the well were reattached to ease sampling throughout the remainder
of the year.  The wells were surveyed to determine water table elevations; those
elevations were then used to determine the direction of groundwater flow. Depth to
groundwater was determined on most sampling dates to determine fluccuations in water
table elevations (Table 1).
Over the duration of the study, eighteen water samples were collected from each
well for nitrate analysis. Nitrate-nitrogen concentrations as well as those of organic and
ammonium nitrogen and chlorides were analyzed by a lab in the UW-Madison Soil
Science Department.
Sixteen samples from each well were collected and analyzed for atrazine
concentrations by the State Lab of Hygiene. Samples taken before 10/25/90 were
analyzed for parent atrazine only. From 11/26/90 - 2/4/91 detects of the atrazine
metabolites, deethy and deisopropylatrazine were recognized. After 2/4/9 1, numerical
results were reported for these two metabolites. By 3/23/93, a third metabolite,