.       A STUDY OF NITRATE AND ATRAZINE CONCENTRATIONS IN GROUNDWATER
FROM AGRICULTURAL USE ON A SANDY, IRRIGATED CORN FIELD IN THE
LOWER WISCONSIN RIVER VALLEY
WCe   esrUes Center
.75. W.IJQw Drive
INTRODUCTION
The Lower Wisconsin River Valley (LWRV), from Prairie du Sac to Boscobel, is
a broad level valley consisting of sandy soils over deep, coarse textured unlithified-
subsurface materials. This area represents one of the most hydrogeologically vulnerable
settings in the state: a shallow sand and gravel aquifer under irrigated, coarse-textured
soils.
The LWRV is an intensively farmed area consisting of irrigated and non-irrigated
fields. Because of this high degree of agricultural use combined with the physical
characteristics of the area, numerous studies have been conducted in the recent past
years to determine the nature and extent of groundwater contamination.
AIn 1989, the Department of Natural Resources (DNR) sampled approximately 50
domestic wells (mostly shallow sandpoints) from Arena to Lone Rock and found atrazine
in about half of the wells and concentrations of nitrate (N03-N) often exceeding the
drinking water standard of 10 ppm.
-Ciba Geigy (the manufacturer of atrazine) conducted a study in July, 1989 in the same

area of the river valley using 27 irrigation wells where the screened interval was usually