Condições atmosféricas e volumes de aplicação na dessecação de Urochloa ruziziensis e vegetação espontânea

Abstract

In the desiccation of the vegetation cover, failures are of common occurrence, resulting from insufficient deposition of herbicides. Thus, it becomes important to know the factors that may interfere in the application. The present work aimed to investigate the efficiency of the pulverization of spray volumes in different weather conditions. The applications were carried out during the day for desiccation of Urochloa ruziziensis and spontaneous vegetation for no-tillage establishment. It was adopted a randomized block design with four replications in a split plot scheme of 2 x 4. The plots consisted of application volumes (50 and 200 L ha-1); and the subplots consisted of different atmospheric conditions obtained by applying at different times (4:30, 10:30, 16:30 and 22:30 hours) throughout the same day. In the application, it was used a customized sprayer, pressurized by CO2 with the spray nozzle model 110015 TT generating mean drops. It was used glyphosate herbicide at a dose of 1.3 kg a.e. ha-1. At 5, 10, 15, and 20 days after herbicide application, it were performed visual assessments of the percentage of control of the vegetation cover. Weather conditions (air temperature, relative humidity, wind speed, and irradiance) found in the application schedules exerted no influence on the efficacy of the herbicide in control of U. ruziziensis in both application volumes. Reducing the spray volume had influence on the control effectiveness of the natural vegetation in all weather conditions where the herbicide was applied.