Tebuthiuron Persistence and Distribution in Some Semiarid Soils

Abstract

AbstractTebuthiuron (N[5‐(1,1‐dimethylethyl)‐1,3,4‐thiadiazol‐2‐yl]‐N,N'‐dimethylurea) is a soil‐applied herbicide used on rangelands to control weeds and brush. This study was conducted at five previously treated semiarid rangeland locations in northcentral Arizona to determine how long tebuthiuron remains in the soil and to what depths it penetrates into the soil. Treatments were made from 1975 through 1979. Soils were collected from 1980 through 1986 at 0‐ to 7‐cm, 7‐to 15‐cm, and successive 15‐cm layers to bedrock or into caliche layers from the perimeter of 3‐ by 0.5‐m trenches dug perpendicular to the long axis of the plots. Tebuthiuron was assayed using gas chromatography with flame photometric detection. Tebuthiuron was detected in soil 11 yr after application. Most of the tebuthiuron detected was in the surface 30 cm of soil during the first 5 yr, but small amounts were detected as deep as 105 cm 6 and 9 yr after treatment. After 9 yr from 55 to 73% of the tebuthiuron detected was at the depth of between 60 and 90 cm.