Posicionamento de herbicidas isolados e/ou associados na dessecação pré-colheita de soja X-Tend-Intacta

Abstract

Pre-harvest desiccation in the soybean production system contributes to weed control, homogenization, and uniformization of soybean plants prior to harvest. In light of the aforementioned, the aim of this study was to evaluate the optimal positioning of isolated or combined herbicides in the pre-harvest desiccation of X-Tend-Intacta soybeans. For this purpose, a field experiment was conducted at the Experimental Farm of Agricultural Sciences (FAECA) of the Federal University of Grande Dourados - UFGD. The experimental design was randomized complete blocks, with the application of the following herbicide treatments at the R7.3 phenological stage of soybeans: glufosinate (400g ha-1); saflufenacil (70g ha-1); flumioxazin (50g ha-1); carfentrazone (20g ha-1); diquat (400g ha-1); tiafenacil (67.8g ha-1); diquat + flumioxazin (747 + 50g ha-1); diquat + amicarbazone (747 + 100g ha-1); diquat + carfentrazone (300 + 20g ha-1); diquat + glufosinate (300 + 300g ha-1); diquat + tiafenacil (300 + 50.35g ha-1); diquat + saflufenacil (300 + 35g ha-1); glufosinate + saflufenacil (300 + 35g ha-1); glufosinate + flumioxazin (300 + 20g ha-1); glufosinate + carfentrazone (300 + 20g ha1); and glufosinate + tiafenacil (300 + 50.35g ha-1), in addition to the control without herbicide application. At 3, 5, 7, and 10 days after application (DAA), visual assessments of phytotoxicity and defoliation were conducted, and photos of the plots were taken for plant desiccation analysis using ImageJ software, grain moisture content was also measured. At the end of the evaluations, productivity and 1000-grain weight were analyzed. The data were subjected to Deviance analysis at 5% significance for all variables using the F-test, and the Shapiro-Wilk test was applied to check for normality. In the presence of interaction between factors, they were further analyzed using the Tukey test (5% significance) and GAMLSS regression. None of the isolated or combined herbicides showed differences in the evaluation of the percentage of desiccated area using ImageJ software, grain moisture content, and 1000-grain weight. However, when evaluating phytotoxicity and defoliation, there was significance among the herbicide treatments. Considering the climatic conditions during the study, the herbicide diquat provided a rapid effect on phytotoxicity and defoliation. On the other hand, glufosinate ammonium exhibited a slower desiccating effect. Among the PROTOX-inhibiting herbicides, tiafenacil stood out for its rapid phytotoxic action due to a higher accumulation of protoporphyrin IX. When saflufenacil was combined with glufosinate ammonium, it had a faster desiccating effect compared to applied alone. Ultimately, the desiccation practice led to higher productivity with the use of the diquat herbicide compared to the control without application.