Effect of Atrazine on Nitrogen Metabolism of Resistant Species

Abstract

In field experiments, corn (Zea mays var. Dixie 18) and Johnsongrass (Sorghum halepense) seeds were planted in Norfolk sandy loam soil and treated preemergence with 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) at 0, 2, 4, and 16 lb/A. In growth chamber studies, corn seeds were planted in flats of Independence loamy fine sand and treated pereemergence with atrazine at 0, 2, and 4 lb/A. In nutrient culture studies, corn was treated with 0, 2, 4, and 8 ppmw atrazine. Treated plants of all species and rates tested usually were smaller than untreated plants and contained higher nitrogen percentages. Corn and Johnsongrass plants treated with high rates of atrazine always contained less nitrogen (mg/plant) than untreated plants. Atrazine-treated corn plants contained higher percentages of both 80% ethanol soluble and insoluble nitrogen than the checks. Percentage increases in both fractions were proportional to the rate of atrazine treatment. Nitrate percentages also were increased, but free ammonia content was not significantly affected.