DOES PREVIOUS ATRAZINE HISTORY ENHANCE ATRAZINE DEGRADATION IN US SOILS? T. C. Mueller*1, W. S. Curran2, R. Scott3, C. Sprague4, D. Stephenson5, D. Miller6, E. Prostko7, W. Grichar8, J. Martin9, L. Krutz10, K. Bradley11, L. E. Steckel12, M. L. Bernards13, M. D. Owen14, P. A. Dotray15, R. Currie16, S. A. Clay17, S. Z. Knezevic18, V. M. Davis19, R. Klein20; 1University of Tennessee, Knoxville, TN, 2Penn State University, University Park, PA, 3University of Arkansas, Lonoke, AR, 4Michigan State University, East Lansing, MI, 5LSU AgCenter, Alexandria, LA, 6Louisiana State University, St. Joe, LA, 7University of Georgia, Tifton, GA, 8Texas A&M AgriLife Research, Lubbock, TX, 9University of Kentucky, Princeton, KY, 10Mississippi State University, Stoneville, MS, 11University of Missouri, Columbia, MO, 12University of Tennessee, Jackson, TN, 13Western Illinois University, Macomb, IL, 14Iowa State University, Ames, IA, 15Texas Tech University, Texas A&M AgriLife Research and Extension Service, Lubbock, TX, 16Kansas State University, Manhattan, KS, 17SDSU, Brookings, SD, 18University of Nebraska, Concord, NE, 19University of Wisconsin, Madison, WI, 20University of Nebraska, North Platte, NE (265)


The literature suggests that atrazine dissipation in surface soils can be more rapid once microbes adapt to the presence of the triazines.  This research surveys soils from across the corn growing  region in the United State to determine how widespread this enhancement is at this time.  A sub-sample of each soil was dried and shipped to MidWest Labs in Omaha, Nebraska.   Each sample was assessed for various soil parameters including nutrient levels, OM, and texture.

Each soil was examined using the following procedure.  A portion of each soil sample was placed into a 500 mL Styrofoam Squat cup in which 5 holes have been placed.  Add water to each sample to saturate the soil.  Allow to drain for 24 hours.  Place ~ 5.0 grams of each soil into a 20 mL glass vial for later atrazine fortification.  This established each soil at a moist, near field-capacity status.

Each vial was then fortified with an aqueous atrazine solution that was incubated at a constant temperature for a time course is -1, 0, 3, 7, 14, 21, 28 and 42, with duplicate samples of each.  The -1 DAT sample is to quantify any residual atrazine or metabolite. Subsequent analysis showed few detections of atrazine in any of the soil samples.  Each vial was stored in a freezer at the appropriate DAT, and all samples within an experiment analyzed at the same time by adding methanol, shaking, filtration, and analysis on LC-MS.  Lab analysis determined parent and the 3 major metabolites simultaneously, with adequate recoveries.  All soils had similar recovery, with initial atrazine concentrations being ~ 2200 ppb .

Since we are only looking at fields with 0 or 5+ years of atrazine use, we are seeing if enhanced atrazine degradation is a widespread, region-wide phenomenon, and not determining how many years of exposure are needed for the enhancement.  Another factor not considered is the atrazine use rate, which varies depending on the region of the country.  Enhanced atrazine degradation was observed in most states, with enhancement indicating reduced residual weed control where atrazine was used in multiple consecutive years.