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Corn - Atrazine Use Precautions and Restrictions

University of Kentucky Cooperative Extension Service Bulletin (AGR-6)
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Herbicide products which contain atrazine (i.e. AAtrex, Basis Gold, Bicep II Magnum, Bullet, Cinch ATZ, Confidence Xtra, Degree Xtra, Expert, FieldMaster, FulTime, G-Max Lite, Guardsman Max, Harness Xtra, Keystone, Lexar, Liberty ATZ, Lumax, Marksman, ReadyMaster ATZ, Simazat, Stalwart Xtra, Steadfast ATZ, Sterling Plus, Stratos, Volley ATZ, etc.) have special label restrictions for use near ground or surface waters. Current label guidelines emphasize the use of low rates, buffer zones, and conservation tillage practices as methods for reducing the risk of contamination of water sources. The maximum rate of these herbicide products for early preplant, preplant incorporated, or preemergence applications depends on soil erodibility, as defined by the Natural Resources Conservation Service, and percent of ground covered with plant residue.

Rate Restrictions:

Atrazine - For soils that are not highly erodible the maximum use rate for atrazine is 2.0 lb ai (active ingredient) per acre. For highly erodible soils the maximum rate is also 2.0 lb ai per acre if conservation tillage is utilized and at least 30% of the soil is covered with plant residue. If ground cover is less than 30%, the maximum atrazine rate is 1.6 lb ai per acre for highly erodible soils. If a postemergence treatment is used following a soil-applied atrazine treatment, the total amount of atrazine applied to a field should not exceed 2.5 lb ai per acre per calendar year. The rate for postemergence applications should not exceed 2.0 lb ai per acre if no previous atrazine applications were made.

Setbacks - Caution is needed when mixing, loading, or applying atrazine near sources of water. According to label directions, atrazine containing products should not be mixed or loaded within 50 feet of wells (including abandoned wells, drainage wells, or sink holes), rivers, intermittent streams, lakes, or reservoirs. This setback does not apply to the use of properly designed impervious pads and properly diked mixing/loading areas.

These products should not be applied within 50 feet of wells or sink holes, within 66 feet of points where field surface water enters permanent or intermittent streams or rivers, or within 200 feet around lakes or reservoirs. If applied to highly erodible soils, the 66 feet buffer area must be planted to a crop or seeded with grass. When atrazine is to be applied near tile riser pipes applicators can choose to: 1) use a 66 feet setback buffer around the tile riser pipes; 2) apply atrazine products if field is no-till and high crop residue management is used; or 3) incorporate atrazine products in the soil to a depth of 2-3 inches.

Some situations will require a high level of management in order to comply with these restrictions. The maximum labeled rate of atrazine may not be sufficient to provide season-long control of some problem weeds. Therefore, more emphasis may be needed on using postemergence herbicides, tillage, or crop rotation to help manage such problem weeds as burcucumber, cocklebur, morningglories, giant ragweed, and velvetleaf.

© 2004, University of Kentucky.

For problems, questions, or permission to reprint information from this website, please contact Mike Marshall. Last Update: 11/01/04.