Non-selective and residual herbicides are commonly associated by farmers to manage no-tillage areas. This practice allows controlling the winter crop to be used as cover crop and to avoid weed reinfestation during part of the summer crop cycle. The objective of this work was to determine the persistence of the residual herbicide S metolachlor when associated to the non-selective herbicides paraquat and glyphosate. The work was carried out under field conditions at the Estação Experimental Agrônomica of the Universidade Federal do Rio Grande do Sul (EEA/UFRGS), and in a growth chamber of the Faculdade de Agronomia of the UFRGS under typical Dystrophic Red Argisol composed by 28% clay. The experiment was arranged in a randomized block design with four replications, with the treatments distributed in split plots .The non-selective herbicides (paraquat, 600 g ha-1 or glyphosate 720 g ha-1) were applied in the main plots, and the residual herbicide S-metolachlor (2.800 g ha-1) in the sub plots, associated or sequentially applied with the non-selective herbicides, plus one control with only non-selective herbicides being applied. The persistence of S-metolachlor is higher in the presence of paraquat when compared to glyphosate. No difference was found between simultaneous and sequential applications of the non-selective and residual herbicides.
bioassay; dissipation kinetics; half-life; residual
