Droplets size categories and application volumes in burndown of plant covers

Abstract

This study has aimed to verify the influence of the droplets size categories and application volumes on burn down Urochloa ruziziensis and Conyza sp. Therefore, two trials were conducted in a randomized block design with four replications in a 2x4 split plot arrangement. The plots consisted in droplets size categories (very fine droplets and ultra coarse droplets) and the subplots consisted in four application volumes (50, 100, 150 and 200 L ha^-1). For desiccation, glyphosate herbicide was used at 0.975 and 1.3 kg of a.e. ha^-1 for controlling plant covers Urochloa ruziziensis and Conyza sp., respectively. Saflufenacil herbicide was used at a dose of 49 g of a.i. ha^{-1 in association with glyphosate to control Conyza sp. In the application was used a pressurized sprayer by CO}₂ with spray nozzles model ATR 1.0 and AI 110015. At 5, 10, 15 and 20 days after application (DAA) of the herbicides, visual assessments were done of the control percentage of Urochloa ruziziensis and defoliation in Conyza sp. At 25 DAA, one regrowth percentage assessment of Conyza sp. plant was done. It is concluded that the category of ultra coarse droplets is efficient for desiccation of Urochloa ruziziensis with volumes of up to 50 L ha^-1, while the category of very fine droplets reduces the efficacy with reduced volume application. It was also found that reducing the application volumes increases the possibility of regrowth on burn down Conyza sp.