Manejo de dessecação na pré-colheita da soja com uso isolado de florpirauxifeno-benzílico e associados a protox em diferentes estádios fenológicos em comparação ao diquat

Abstract

Pre-harvest desiccation of soybean is a practice of high agronomic importance, as it contributes to the uniformity of maturation, reduction of grain water content, anticipation of harvest, and better organization of the sowing of the subsequent crop, especially in production systems in Mato Grosso do Sul, where soybean precedes second-crop maize. In addition, proper desiccation management reduces crop exposure to rainfall, pests, diseases, and qualitative losses, favoring the maintenance of grain yield and quality. In this context, the objective of this study was to evaluate the best application timing of florpyrauxifen-benzyl, applied alone, associated with PROTOX-inhibiting herbicides, or supplemented with vegetable oil, compared with diquat, in the pre-harvest desiccation of soybean at the R7.1, R7.2, and R7.3 phenological stages. The experiment was conducted under field conditions in a randomized block design, with four replications, in a factorial scheme composed of three application stages, seven herbicide treatments, and untreated controls. The plots were subjected to treatments with florpyrauxifen-benzyl, florpyrauxifen-benzyl + vegetable oil, associations with carfentrazone, flumioxazin, saflufenacil, and tiafenacil, in addition to diquat. Defoliation, desiccation, grain water content, pod and grain maturation, membrane damage, and grain yield were evaluated, with statistical analyses performed using GAMLSS models and mean comparisons by Tukey’s test at 5% probability. The results showed that diquat exhibited the highest speed of action in all evaluated stages, promoting rapid defoliation and desiccation due to its contact mechanism associated with Photosystem I. However, this more intense action was also related to greater membrane damage and the possibility of early interruption of final physiological processes. Treatments with florpyrauxifen-benzyl showed a more gradual response, consistent with its systemic mechanism and auxin-mimicking mode of action, whereas associations with PROTOX-inhibiting herbicides intensified desiccation effects and cellular damage. At the R7.2 stage, the highest yields were observed for florpyrauxifen-benzyl + carfentrazone and florpyrauxifen-benzyl + vegetable oil, with values close to 5,900 kg ha⁻¹. At the R7.3 stage, yields were higher and more uniform among treatments. Thus, it was concluded that diquat showed greater desiccation efficiency at the R7.1, R7.2, and R7.3 stages, and that there were no significant differences among these treatments, except for the yield increase observed with florpyrauxifen-benzyl + carfentrazone and florpyrauxifen-benzyl + vegetable oil at R7.2, indicating their potential as alternatives for anticipating pre-harvest desiccation. Furthermore, the differences among herbicides decreased as the phenological stages advanced, indicating that the closer the crop is to physiological maturity, the lower the influence of herbicides on desiccation.