Efficacy of S-metolachlor plus glyphosate for Weed Control in Different Levels of Eucalyptus Straw

The occurrence of weeds in eucalyptus plantations can cause losses in productivity. Chemical control is widely used, but the efficiency of herbicides depends on management and environmental factors. This study aims to evaluate the efficiency of S-metolachlor + glyphosate in the control of grasses in different densities of eucalyptus straw and with simulated rainfall after application of the product. The experiment was conducted in a randomized block design, factorial, with four replications. The first factor represented 0; 1.06 + 0.79 e 2.12 + 1.59 kg i.a. ha(-1) of the commercial dose of S-metolachlor + glyphosate, the second 0; 5 and 10 tons ha(-1) of straw and, the third 25 and 50 mm of water depth applied in soil with a mix of grasses previously sowed. The evaluations carried out were fresh mass, dry mass, and visual analysis of the control percentage. The fresh and dry mass and the grasses' dry mass/water ratio decreased with increasing herbicide dosage and straw density. The treatments without straw and with the herbicide application had the highest percentages of control, the highest in the dosage of 2.12 + 1.59 kg i.a. ha(-1) of S-metolachlor + glyphosate. Applying different water depths (25 mm or 50 mm) did not influence the control. In conclusion, it was observed that the isolated straw promoted the control of grasses. However, in treatments that included straw and herbicide, there was a decrease in the efficiency of the product, which suggests an antagonism between the vegetation cover and S-metolachlor + glyphosate.