Combination of Pre-emergence Herbicides for Weed Control in Soybean

Pre-emergence herbicides supress weeds in soybean, enabling the crop to stablish without competition. Therefore, this study aimed to evaluate the selectivity of pre-emergence herbicide combinations in soybean and their effectiveness in controlling weed species. A field experiment was conducted using a randomized block design with four replications. Treatments included two controls (weeded and unweeded) and ten combinations of pre-emergence herbicides: sulfentrazone + diuron; sulfentrazone + clomazone; sulfentrazone + imazethapyr; flumioxazin + imazethapyr; flumioxazin + pyroxasulfone; s-metolachlor + flumioxazin; s-metolachlor + diclosulam; s-metolachlor + fomesafen; s-metolachlor + metribuzin and flumioxazin + imazethapyr + s-metolachlor. Herbicides were applied in a plant-and-spray system. The weed species evaluated were Bidens pilosa L., Commelina benghalensis L., Digitaria insularis L., Euphorbia heterophylla L. and Ipomoea purpurea L. E. heterophylla had the lowest germination flow in the sulfentrazone + clomazone treatment group, which was close to 0 plants/m², obtaining about 90% control at 14 DAE, whereas the sulfentrazone + imazethapyr mixture showed control below 20% at 21 DAE and between 20% and 40% at 28 DAE. D. insularis showed low germination flow in all treatments except for sulfentrazone + imazethapyr, s-metolachlor + metribuzin and flumioxazin + imazethapyr, with 1, 2 and 4 plants/m² and, respectively. The combinations of pre-emergence herbicides contributed to an increased spectrum of weed control and no herbicide combination showed significant phytotoxicity to the soybean crop. Compared with the untreated control treatment, the majority of the treatments resulted in an increase in crop yield, with most showing a yield increase of 814 kg ha-¹ compared to the unweeded control.