Eficácia do florpirauxifeno-benzílico em associação com herbicidas na dessecação pré-colheita da soja e efeito de horários de aplicação na ação do diquate

Abstract

Pre-harvest desiccation of soybean is a management practice used to standardize maturation, anticipate harvest, and reduce the risk of losses and deterioration, highlighting the need to evaluate herbicides as alternatives to paraquat and to understand how interactions with the environment affect their effectiveness. Thus, the objective of this study was to evaluate the efficiency of florpyruxifen-benzyl applied alone and in association with the herbicides diquat, tiafenacil, flumioxazin, ammonium glufosinate, amicarbazone, and carfentrazone-ethyl in soybean pre-harvest desiccation, as well as to assess the effect of different application times on the performance of diquat. The study was conducted in two distinct experiments. Experiment 1 was carried out during the 2023/24 growing season, in a randomized complete block design (RCBD), with seven treatments and four replications, and experiment 2 was conducted during the 2024/25 growing season, also in RCBD, with eight treatments and four replications. In experiment 1, agronomic performance and the dynamics of light action after pre-harvest application of diquat were evaluated. Light dynamics were assessed by applying diquat at different times of the day in order to provide distinct periods of light exposure following application. Thus, treatments with 12, 8, and 4 hours of light or darkness immediately after application were established, as follows: T1 – 12 hours of light (06:20); T2 – 8 hours of light (10:20); T3 – 4 hours of light (14:20); T4 – 12 hours of darkness (18:20); T5 – 8 hours of darkness (22:20); T6 – 4 hours of darkness (02:20); and T7 – untreated control, allowing the evaluation of the effect of light exposure duration on the speed of herbicide action. In experiment 2, defoliation and desiccation (visual assessment and ImageJ analysis), moisture reduction over days after application (DAA), electrical conductivity (EC), thousand-grain weight (TGW), and yield were evaluated. The applied treatments were as follows: T1 – diquat (0.5 L ha⁻¹) + florpyruxifen-benzyl (0.1 L ha⁻¹); T2 – tiafenacil (0.3 L ha⁻¹) + florpyruxifen-benzyl (0.1 L ha⁻¹); T3 – flumioxazin (0.05 L ha⁻¹) + florpyruxifen-benzyl (0.1 L ha⁻¹); T4 – ammonium glufosinate (0.26 L ha⁻¹) + florpyruxifen-benzyl (0.1 L ha⁻¹); T5 – amicarbazone (0.13 L ha⁻¹) + florpyruxifen-benzyl (0.1 L ha⁻¹); T6 – florpyruxifen-benzyl applied alone (0.1 L ha⁻¹); T7 – carfentrazone ethyl (0.6 L ha⁻¹) + florpyruxifen-benzyl (0.1 L ha⁻¹); and T8 – untreated control. For the different diquat application times, no statistical difference was observed between treatments and the control when defoliation was evaluated. All treatments promoted greater desiccation than the control, reaching 100% desiccation at the end of the evaluation period, whereas the control reached a maximum of 93.25%. Regarding grain moisture, all treatments were superior to the control, with diquat applications at different times resulting in moisture contents between 13% and 16%, while the control remained above 19%. Treatments with 12, 8, and 4 hours of light exposure immediately after application resulted in the lowest moisture contents (below 14%) at the end of the evaluation period. Different application times did not influence final crop yield, with no statistical differences observed between treatments and the control. The use of florpyruxifen-benzyl, both alone and in association with other herbicides, showed superior performance compared to the control in terms of defoliation and desiccation, with no significant differences among treatments at the end of the evaluation period. However, treatment T1 (diquat + florpyruxifen-benzyl) achieved 100% desiccation and defoliation in a shorter time compared to the other treatments and the control. Regarding grain moisture, all herbicide treatments showed superior performance, and significant differences among treatments were observed at the end of the evaluation period. Treatments T1 (diquat + florpyruxifen-benzyl), T2 (tiafenacil + florpyruxifenbenzyl), and T6 (carfentrazone-ethyl + florpyruxifen-benzyl), in addition to achieving the lowest moisture contents (below 14%), also showed potential to anticipate harvest by up to seven days compared to the control and by two days compared to the other treatments. For TGW and yield, all treatments were superior to the control. It is concluded that diquat application times that allow greater exposure to sunlight immediately after application promote greater moisture reduction without affecting final yield. The use of florpyruxifen-benzyl associated with diquat (T1) promotes faster desiccation, defoliation, and moisture reduction, and together with treatments T2 (tiafenacil + florpyruxifenbenzyl) and T6 (carfentrazone-ethyl + florpyruxifen-benzyl), shows potential to anticipate soybean harvest by up to seven days compared to the control, while the other treatments anticipate harvest by up to five days compared to the control.