Pre‐emergent herbicides are key tools in managing herbicide‐resistant and hard‐to‐control weed species in soybean ( Glycine max L.) cultivation. This study aimed to evaluate the effects of pre‐emergent herbicides on weed phytosociology, soybean phytotoxicity, and grain yield under different soil management systems and environmental conditions. Four field experiments were conducted in Brazil (Santo Ângelo and Santa Maria) using a randomized block design across two growing seasons and tillage systems (no‐till and conventional). Herbicide treatments included single and combined active ingredients, applied in the plant‐and‐apply modality. Weed surveys were conducted at 25 and 40 days after emergence (DAE) to calculate the relative importance value index (IVIR), diversity (Simpson and Shannon–Wiener), and similarity indices. Sulfentrazone, trifluralin, and s‐metolachlor caused significant phytotoxicity, especially in conventional systems. Herbicide efficacy varied by species and management system. Pyroxasulfone + flumioxazin, metribuzin, and chlorimuron‐ethyl significantly reduced the IVIR of dominant species like Raphanus raphanistrum and Euphorbia heterophylla . Despite observed phytotoxicity, some herbicide combinations improved yield without compromising crop safety. These results underscore the importance of integrating herbicide selection with soil management to optimize weed control and maintain soybean productivity.
Grün et al. (Thu,) studied this question.