The effect of soil-applied and post-emergence herbicides on the level of weed infestation in soybean crops. Grain Crops. 2024. 8 (1). 162–171.

Topicality. The high weed infestation is a limiting factor that slows the growth of soybeans area and yield, which is influenced by anthropogenic factors, biological properties of weed communities and crops. Herbicide use remains one of the most important elements of intensive soybean production. Herbicide application remains one of the most important elements of intensive soybean cultivation. As weeds become more resistant to certain active ingredients, there is a demand to study the effectiveness of new herbicides and their combinations. Purpose. To study the effect of soil-applied and post-emergence herbicides on the weed infestation in soybean crops. Methods. Field, laboratory, measuring and weighing, mathematical. Results. The observations showed that weather conditions had a significant effect on the weed infestation in the soybean crop. In 2021, the highest number of weeds by species (an average of 203.2 plants/m2) was recorded in the registration plots. In 2022 and 2023, the numbers were 141.3 and 189.2 plants/m2, respectively. The segetal vegetation was dominated by representatives of the monocotyledonous class, the grass family (50.7 %) and dicotyledons (43.1 %), and the percentage of perennials was only 5.8 %. The application of Primextra TZ Gold 500 SC (4.5 l/ha) and Frontier Optima (1.2 l/ha) and Stomp 330 (5 l/ha) at the third trifoliate leaf stage (BBCH 12) resulted in reduction in the amount of segetal vegetation in the crops of the soybean varieties under study by 71.4–84.5 % and in their dry weight – 63.2–81.7 %. Before harvesting the crop, the effect of soil-applied herbicides Primextra TZ Gold 500 SC (4.5 l/ha) and Frontier Optima (1.2 l/ha) + Stomp 330 (5 l/ha) was decreased, and the application of post-emergence herbicides Bazagran (3 l/ha) + Fusilade Forte 150 ES (1 l/ha) and Corum (2 l/ha) + Achiba (2 l/ha) was more effective. Conclusions. The most effective variant of controlling segetal vegetation in soybean crops of varieties Aurelina, ES Komandor and ES Navigator was the post-emergence application of herbicides Bazagran (3 l/ha) + Fusilade Forte 150 ES (1 l/ha) and Corum 2 l/ha) + Achiba (2 l/ha) in the stage of 2–4 leaves of the crop, which reduces the number of weeds by 91.3–95.8 % and their dry weight by 90.1–95.1 %. Key words: soybean, herbaceous vegetation, weed species composition, number of weeds, dry weight