Tebuthiuron is one of herbicides most used on sugar cane in the state of São Paulo. Studies have been carried out to determine tebuthiuron leaching index and to monitor its presence in surface and groundwater sources, with no definitive conclusion been reached yet. The aim of this research was to evaluate the vertical movement of tebuthiuron under field conditions on Clayey Dystroferric Red Soil. The tested hypothesis was based on the low vertical mobility and small potential of groundwater contamination by tebuthiuron. The trial was carried out at the Experimental Field College of Agricultural Engineering UNICAMP, using a modified drainage lysimeter, 2 meters of diameter and 3 meters depth, with 10 vertical points where rain water samples were collected. The samples were submitted by High Performance Liquid Chromatography (HPLC).The data found indicated a decreasing presence of the herbicide in the samples collected through time March to August, 2006: sample 1 - 0.020 g a.i. (5.3%); 2 - 0.016 g a.i. (4.3%); 3 - 0.015 g a.i. (4.0%); 4 - 0.014 g a.i. (3.7%); 5 - 0.014 g a.i. (3.7%); 6 - 0.007 g a.i. (1.9%); 7 - 0.002 g a.i. (0.5%); 8 - 0.001 g a.i. (0.3%) - total applied in the lysimeter area (0.3768 g i.a.), confirming the hypothesis that tebuthiuron vertical mobility is low in Clayey Dystroferric Red Soil, with clayey texture, indicating small potential of groundwater contamination on this soil.
herbicide; leaching; vertical mobility; groundwater
