ADDITION OF AMMONIUM SULFATE TO GLYPHOSATE IN THE DESICCATION OF Urochloa Brizantha CV. BRS “PIATÃâ€

Resumo

Abstract: Background: Glyphosate is the most widely used herbicide in Brazilian agriculture, and management techniques that increase its efficacy are important tools for the production system.

Objective: The aims of this study were to assess the effect of adding the nitrogen adjuvant ammonium sulphate [(NH₄)₂ SO₄] to glyphosate on the control of Urochloa brizantha BRS Piatã and establish the best [(NH₄)₂ SO₄] dose to mix with the herbicide.

Methods: To that end, two greenhouse experiments were conducted. In the first, six glyphosate doses (0; 33.75; 67.5; 135; 270; 540 g. ae. ha^-1) were used to determine C80 (glyphosate dose that achieved 80% control of BRS Piatã grass). This dose was used as a reference for the second experiment, in a mixture with four [(NH₄)₂ SO₄] doses (0; 6.67; 13.33; and 20 g L^-1 of solution) to determine the best nitrogen adjuvant dose. In both experiments, BRS Piatã grass control was assessed at 7, 14 and 21 days after treatment (DAT), and shoot length and dry weight at 21 DAT.

Results: While the C₈₀ of glyphosate was established at 270 g. ae ha^-1. The visual scale indicated that adding [(NH₄)₂ SO₄] accelerated the glyphosate-related symptoms but did not change plant fresh and dry weight and shoot length. Maximum glyphosate efficacy was obtained by adding ammonium sulphate at a concentration of 16.2 g L^-1 of solution. Conclusions: Ammonium sulphate accelerates the glyphosate mode of action in the desiccation of Urochloa brizantha BRS Piatã.