Persistence and leaching of ametryn and trifloxysulfuron-sodium on sugar-cane soil

摘要

The aim of the work was to evaluate the behavior of the ametryn + trifloxysulfuron-sodium commercial mixture in sugar-cane crop, as related to leaching potential and persistence in the environment. The Typic Haplufalf soil area was divided into two sub areas where the sugar-cane varieties SP 79 1011 and SP 80 1816 were cultivated. The treatments were constituted by pre and post-emergence applications of the commercial herbicide mixtures in 2003 and 2003 + 2004, with four soil samplings 0-0.10 and 0.10-0.20 m deep. Bioassay and High Performance Liquid Chromatography (HPLC) methods were used to evaluate the residues. Both methods were found satisfactory for evaluation of the commercial mixture residue, although the bioassay use did not allow evaluating the compounds separatedly. According to the data obtained from the simultaneous analysis of ametryn and trifloxysulfuron-sodium by HPLC, most of the ametryn residues remained in the soil layer 0-0.10 m deep, persisting for over 180 days after application (DAA), in soil sprayed in 2003 + 2004. Ametryn residues in 0.10 – 0.20 m deep, were as well found for the treatments sprayed in 2003 + 2004 and showed the risks of leaching and contaminating water with this herbicide. For the treatments sprayed only in 2003, a significant residual effect was not detected 490 days after application. Differences in residual effect among cultivated sub areas with the variety SP 79 1011 and SP 80 1816 were due to the different amounts of clay and organic matter in the soil. Residues of trifloxysulfuron-sodium were not found in any period of the soil sampling, as the limit of quantification by HPLC (0.06 mg L-1) is higher than the used dose of this herbicide (37 g ha-1).