Seletividade de herbicidas na cultura do sorgo forrageiro

Abstract

The number of registered herbicides for sorghum is still limited for grass control. Thus, the objective of this study was to evaluate the selectivity of herbicides applied in pre and post-emergence, in the culture of forage sorghum. Two experiments were carried out, both in a randomized block design, in a factorial scheme with four replications. The first experiment, the 2016/2017 crop, consisted of the BRS 658 and BRS 655 hybrids. The weed control treatments used were: manual weeding; S-metolachlor (1440 g a.i. ha-1); S-metolachlor (1440 g a.i. ha-1) + atrazine (2000 g a.i. ha-1); atrazine (2000 g a.i. ha-1); atrazine (3000 g a.i. ha-1); atrazine (2000 g a.i. ha-1) + mineral oil (0.25%) and atrazine (2000 g a.i. ha-1) + mineral oil (0.5%). The second experiment occurred during the 2018/2019 harvest and the first factor corresponded to the four hybrids of forage sorghum (MSE 321, BRS 658, BRS 659, VOLUMAX) and the second factor corresponded to the herbicides applied in post-emergence where the four treatments were witness (weeding); mesotrione + atrazine + 0.2% oil (24g + 2000 g a.i. ha-1); atrazine + 0.2% oil (2000 g a.i. ha-1); and bentazone + 0.2% oil (720 g a.i. ha-1). The evaluated parameters were phytotoxicity, plant height at 28 DAA (days after application) and final height, final stand and dry matter productivity. Atrazine applied post-emergence at a dose of 2000 g a.i. ha-1 is selective for sorghum cultivars. The use of mesotrione + atrazine + oil is not selective for forage sorghum.