Determination of control dose of Urochloa decumbens by the glyphosate application

Abstract

The species Urochloa decumbens is an important weed of agricultural crops due to the high adaptive capacity and difficulty of management. The presence of these plants into agricultural production areas can cause serious problems when it competes for water, light and nutrients, besides acting as host of pests and common pathogens to the crop and interfering in harvesting. The study aimed to evaluate doses of control of U. decumbens plants by glyphosate application. Three experiments were conducted, in greenhouse in completely randomized design with six replications, containing between 50 and 80 plants per replication, and eight doses of glyphosate (0, 22.5, 45, 90, 180, 360, 720 and 1440 g ha-1 a.e.). Visual evaluations of injury were performed at 0, 7, 14 and 21 days after application, and collecting eight plants per pot and per treatment to determine dry mass in each evaluated time. For the response curves, the total dry mass was considered, adding all the collected times and the remaining plants from the pots at the end of the experiments. U. decumbens plants treated with 180 g ha-1 a.e. of glyphosate reduced the dry mass in relation to the control, demonstrating greater sensitivity in the application of doses below those recommended and used in the field. In conclusion, the dose 80 g ha-1 a.e. of glyphosate controlled U. decumbens plants causing injury close to 100% and the estimated doses between 30 and 62 g ha-1 a.e. of glyphosate were able to reduce 50 % of plant growth