Weed control and selectivity of alternative herbicides to glyphosate in soy cultivation

One of the main alternatives found by producers for mitigating the problems caused by the occurrence of resistant weed biotypes is the use of alternative herbicides. The aim of this paper was to evaluate weed control and the phytotoxicity caused by the application of pre-and post-emergent herbicides in soy cultivars that are resistant to glyphosate. Two field experiments were carried out in a random block experimental design, with four repetitions. The treatments were arranged in a factorial design, testing two soy cultivars (Nidera 5909 RG and Coodetec STS 249 RR), four pre-emergent herbicides (s-metolachlor, diclosulan, metribuzin, sulfentrazone) and four post-emergent herbicides (chlorimuron ethyl, imazethapyr, bentazone, carfentrazone ethyl), plus infested and clean samples. Phytotoxicity evaluations of the crop were carried out 7, 14, and 21 days after the emergence (DAE) of soy plants for the pre-emergents; and 7, 14, and 21 days after the application of the herbicides (DAA) for the post-emergents. The weed control evaluation for both experiments was carried out at 14 and 28 DAE, with the exception of Ipomoea spp., at 14 DAE. In pre-emergence, sulfentrazone causes greater phytotoxicity in both cultivars studied, while in post-emergence, carfentrazone ethyl causes the greatest symptoms of phytotoxicity. In pre-emergence, the best Raphanus spp. and Bidens spp. controls were obtained with the application of the herbicides diclosulan and metribuzin, while sulfentrazone and diclosulan provide the best Ipomoea spp. controls. The herbicide sulfentrazone reduces the productivity of the Nidera 5909 RG cultivar, while carfentrazone reduces the productivity of both cultivars.