Interference of adjuvants and nitrogen fertilizers on the efficiency of saflufenacil and ammonium glufosinate in Conyza spp. control.

Resumo

The use of adjuvants and nitrogen fertilizers mixed with herbicides can positively or negatively interfere with weed control efficacy, such as in the case of Conyza spp. The present study aimed to investigate the interference of adjuvants and nitrogen fertilizers added to the spraying solution on the efficacy of the herbicides saflufenacil and ammonium glufosinate on Conyza spp control. The experiments were carried out in a greenhouse under a randomized block design, in a 5x3 factorial scheme with four replications. Factor A consisted of the herbicides saflufenacil (EI) (70 g a.i. ha^-1) and ammonium glufosinate (500 g a.i. ha^-1) (EII) applied individually and in combination with the adjuvants Aureo^®, Assist^®, Dash^® and Agral^®. Factor B included the nitrogen fertilizers ammonium sulfate and urea, in addition to an untreated check. The applications were carried out when plants were at the 13 - 15 cm growth stage. The data were subjected to analysis of variance (ANOVA) and Tukey’s test at a 5% significance level. Regardless of adjuvant or nitrogen fertilizer used in combination with saflufenacil, all treatments showed satisfactory control of Conyza spp, similar to the isolated herbicide. For improved Conyza spp. control with ammonium glufosinate, it is not recommended to mix urea or ammonium sulfate with the Dash^® adjuvant in the spray solution. In contrast, the control efficacy of Conyza spp. with ammonium glufosinate was higher when Agral^® was used in the mixture. The use of adjuvants and/or nitrogen fertilizer in spray tank mixtures with ammonium glufosinate herbicide is essential for effective control of Conyza spp plants.

Keywords: Weed control, Herbicide interaction, Herbicide application, Tank mix.