Processos de retenção, transporte e transformação em solos dos herbicidas diuron, hexazinone e sulfometuronmethyl

Abstract

Knowledge on the processes involved among herbicides and soil is essential to define the application rates, maximizing the control of weeds and minimizing environmental risk caused by the residues of this pesticide. Several processes define the final destination of the herbicide, which can vary according to the physical and chemical characteristics of the soil. In this research, the sorption, desorption, leaching and half-life of the herbicides diuron, hexazinone and sulfometuron-methyl were evaluated in the following soils: Cambissolo Háplico, Latossolo Vermelho and Neossolo Quartzarênico. The sorption and desorption tests were estimated according to the “Batch Equilibrium”, method based on sorption and desorption isotherms. The leaching of herbicides was estimated in PVC columns at seven depths (0 to 0.35 m). The halflife was estimated in pots during times equivalent to 1, 3, 7, 15, 30, 45, 60, 120 and 180 days after application of the herbicide. The detection and quantification of herbicides in the samples of all experiments were analyzed by Ultra High-Performance Liquid Chromatography coupled to the Mass Spectrometer (LC-MS/MS). The sorption of the three herbicides was influenced by the pH and CTC of the studied soils, where the Latossolo showed greater sorption among the soils under the influence of the three herbicides applied. The highest sorption of the three herbicides in the Latossolo had a positive correlation in the half-life results (t1/2), except for hexazinone, whose t1/2 was higher in the Neossolo. Leaching for diuron remained in the upper layers of the soil, while hexazinone and sulfometuron-methyl leached to deeper layers. The GUS index indicated the highest risk of leaching for hexazinone compared to other herbicides in all soils. Hexazinone and sulfometuron-methyl can assist in the control of propagules in deeper layers of the soil, but their environmental risk of leaching must be considered when defining the dose used