Movement of Tebuthiuron Applied to Wet and Dry Rangeland Soils

Abstract

Tebuthiuron was applied at 1 kg ai/ha to wet and dry Hathaway gravelly, sandy loam soil in the spring and fall to determine the amount of tebuthiuron removed in runoff water and the depth to which it would move within the soil profile by simulated rainfall. When pellets containing 20% ai of tebuthiuron were broadcast onto dry soil in the spring, the first simulated rainfall event, 37 mm, removed 5% of the applied tebuthiuron in runoff water and sediment. The second and third simulated rainfall events, 22 and 21 mm, respectively, removed an additional 2%. When tebuthiuron was applied to wet soil in the spring, the initial simulated rainfall events, totaling 42 mm, removed 15% of the tebuthiuron. When tebuthiuron was applied to wet soil in the fall, the initial rainfall events, totaling 40 mm, removed a total of 48% of the tebuthiuron in runoff water and sediment. No significant differences were found in the total amount of tebuthiuron within the soil profile after application to dry and wet soils. More than half of the tebuthiuron had moved into the surface 7 cm 1 day after application. Tebuthiuron was not detected below 90 cm after 165 mm of simulated rainfall and 270 mm of natural rainfall.