Effect of sugarcane coverage on the behavior of tebuthiuron in soil in Brazil.

The region of Ribeirao Preto City located in Sao Paulo State, southeastern Brazil, is an important sugarcane, soybean and corn producing area. This region is also an important recharge area for groundwater of the Guarany aquifer, a water supply source of the city and region. The herbicide tebuthiuron (N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2 yl]-N,N?-dimethylurea) is regularly applied in the area. In order to understand the movement of tebuthiuron, the herbicide was applied at the recommended label rate with and without sugarcane coverage, on sandy soil area in Santa Rita do Passa Quatro County in Brazil, located in the region. Soil samples were collected at each 20 cm down to 120 cm and taken to the laboratory for determination of tebuthiuron. Tebuthiuron was measured at those depths mentioned before in ten intervals of time up to 300 days. Tebuthiuron halflives varied from 69 days in sugarcane cropped area to 49 days in non-cropped area. After 180 days there were no measurable residues in the soil and tebuthiuron was not found below 40 cm depth in any time