Seletividade de misturas de herbicidas em tanque na cultura do trigo

Abstract

Among the set of factors influencing wheat productivity and grain quality, weed infestation stands out. Weeds can compete for water, light, and nutrients, leading to reduced productivity and increased production costs. Thus, the objective of this study was to evaluate the selectivity of herbicides applied either individually or in tank mixtures post-emergence on the TBIO Duque wheat cultivar. The field experiment was conducted in randomized blocks with four replications. The herbicides used were: saflufenacil (49 g ha-1), 2,4-D amine (670 g ha-1), metsulfuron-methyl (3,96 g ha-1), pinoxaden (50 g ha-1), and terbuthylazine (750 g ha-1), applied individually or in tank mixtures, along with two controls—one weeded and one infested. Phytotoxicity was assessed at 7, 14, 21, 28, 35, and 42 days after treatment (DAT). Physiological characteristics including sub-stomatal CO2 concentration (Ci - μmol mol-1), stomatal conductance (Gs - mol m-1 s-1), photosynthetic rate (A - μmol m-2 s-1), transpiration rate (E - mol H2O m-2 s-1), carboxylation efficiency (EC - mol CO2 m-1 s-1), and water use efficiency (WUE - mol CO2 mol H2O-1) were evaluated at 25 DAT. At wheat harvest, grain yield components (spike length, filled grains, sterile grains, spike number, hectoliter weight, thousand grain weight, and grain yield) were determined. Saflufenacil, applied alone or in combination with 2,4-D amine, metsulfuron-methyl, or pinoxaden, caused the highest levels of phytotoxicity to the wheat crop in all assessments. Saflufenacil combined with 2,4-D amine and metsulfuron-methyl caused less injury compared to its sole application. In terms of physiological variables, the tank mixture of all herbicides caused the most damage to the crop. However, treatments applied individually with 2,4-D amine and metsulfuron-methyl were the most selective to wheat. Herbicides that showed the best results in terms of grain yield and yield components were 2,4-D amine, metsulfuron-methyl, saflufenacil + metsulfuron-methyl, 2,4-D amine + metsulfuron-methyl, and 2,4-D amine + metsulfuron-methyl + pinoxaden.