The objective of this work was to evaluate the influence of rainfall on leaching of herbicides recommended for sugarcane crop in Dystrophic Red Latosol. The experiment consisted in spraying trifloxysulfuron-sodium + ametryn (1463 + 37 g ha-1), imazapic (84 g ha-1), imazapyr (200 g ha-1), ¹diuron + hexazinone (1170 + 330 g ha-1) and ²diuron + hexazinone (1330 + 160 g ha-1) on top of PVC columns filled with soil. After spraying, simulated rainfall of 20, 40 and 80 mm was applied on top of the columns. Cucumis sativus (cucumber) was used in bioassays to detect herbicide leaching, with evaluations accomplished 14 and 21 days after application of the treatments. After a 20 mm rainfall simulation, it was verified that the trifloxysulfuron-sodim + ametrin mixtures caused decreasing symptoms of toxicity in the 0 to 20 cm plantules, while the other herbicides had an effect up to 10 cm. The 40 mm rainfall made the mixtures1,2 diuron + hexazinone cause severe symptoms in the cucumber plants at 15 cm depth and decreasing symptoms at depths of 20 cm (formulation 2) and 25 cm (formulation 1). The herbicides trifloxysulfurom sodium + ametryn and imazapyr were detected up to 20 cm of depth. The herbicide imazapic caused toxicity up to 15 cm of depth. At 80 mm rainfall, ¹diuron + hexazinone caused toxicity up to 30 cm and ²diuron + hexazinone, imazapyr, trifloxysulfuron sodium + ametryn and imazapic presented toxicity up to 25 cm of depth. It was concluded that all the herbicides evaluated tend to be leached under the influence of rainfall or artificial irrigations.
sugarcane; rainfall; bioassay; herbicides
