Manejo químico de buva resistente a glyphosate antes e após a semeadura da soja Enlist

Abstract

The horseweed species (Conyza bonariensis, C. canadensis e C. sumatrensis) that infest soybeans stand out as the main weeds that cause significant losses in productivity and quality of harvested grains. Therefore, the objective of this study is to evaluate the efficacy, selectivity, and effect of herbicides on the physiological characteristics and yield components of soybeans with Enlist®️ technology. For this purpose, a field experiment was conducted in randomized blocks with four replications. The treatments used for early management of horseweed (C. bonariensis) were: diquat, ammonium glufosinate, glyphosate, glyphosate + saflufenacil, glyphosate + dicamba, diquat + saflufenacil, diquat + dicamba, ammonium glufosinate + saflufenacil, ammonium glufosinate + dicamba, saflufenacil + dicamba, glyphosate + 2,4-D amine, diquat + 2,4-D amine, and ammonium glufosinate + 2,4-D amine, plus two controls, one infested and the other weeded, totaling 15 treatments. Two days before soybean sowing, diquat + saflufenacil + mineral oil had been applied to the experimental area, with exception in the witness. At V3 to V4 stages of soybeans, herbicides 2,4-D choline + glyphosate had been applied to the experimental area, with exception of witness weeded and infested. Phytotoxicity to the soybean cultivar C2531E and horseweed control were evaluated at 7, 14, 21, 28, 35, and 42 days after the treatment application (DAT) used for early management. Gas exchange variables were measured 40 days after soybean emergence. At soybean harvest, yield components, such as numbers of pods per plant and number of grains per plant, thousand grain weight and grain productivity, were determined. The early application of glyphosate + dicamba, ammonium glufosinate + dicamba, saflufenacil + dicamba, glyphosate + 2,4-D amine, diquat + 2,4-D amine, and ammonium glufosinate + 2,4-D amine, as well as the use of 2,4-D choline + glyphosate for soybean cleaning at V3 to V4, provided efficient horseweed control. None of the herbicides applied before soybean sowing or postemergence caused phytotoxicity to the soybean cultivar C2531E. The early application of diquat + saflufenacil for soybean desiccation and the post-emergence application of 2,4-D choline + glyphosate resulted in the best performance in the physiological variables of the culture. The highest grain yield was observed when ammonium glufosinate had been applied before the use of 2,4-D choline + glyphosate.