The role of herbicide-based weed control in shaping sunflower yield and seed quality in the Western Forest-Steppe of Ukraine

Abstract

Goal – to assess the effectiveness of modern herbicides and their combinations in the weed control system of sunflower crops, as well as to determine their impact on seed yield and quality in the conditions of the western Forest-Steppe of Ukraine. Methods. The research was conducted during 2021–2023 on the experimental field of the Educational and Production Center “Podillia” of the Higher Education Institution “Podillia State University” on typical low-humus, medium-loamy black soil. The repetition in the experiment is fourfold. The placement of variants is systematic. Results. The research was carried out using the preparations Kentavr (1.0 l/ha), Promex (2.0 l/ha), Proxanil 72 % k. e. (2.0 l/ha) and their combination Promex + Proxanil 72 %, k. e. (2.0 + 2.0 l/ha). The analysis showed that the level of weed infestation of crops significantly depended on the biological characteristics of the variety and the herbicide protection scheme. Thus, already at the beginning of the growing season (30 days after emergence) in the control (without herbicides) the number of weeds was 173.3 pcs./m2 in the Belvedere variety and 165.2 pcs./m2 in the Sumatra variety, which indicates the higher competitiveness of the latter. In the variants with the introduction of herbicides, weed infestation was significantly reduced. The most effective was the combined variant Promex + Proxanil, where the number of weeds during the harvesting period decreased to 54.7 pcs./m² in the Sumatra variety and 61.0 pcs./m2 in the Belvedere variety, which corresponded to a decrease of more than 70 % compared to the control. The most common weed species was white quinoa (Chenopodium album L.), the share of which in the structure of crop contamination in the control reached 72–77 %. After the application of herbicides, its share decreased to 30–36 %, which confirms the high effectiveness of the drugs against dicotyledonous species. A synergistic effect between varietal characteristics and the action of herbicides was established, in which the rapid closure of rows and active growth of plants of the Sumatra variety enhanced the phytotoxic effect of the drugs. Effective weed control had a positive effect on yield. In the control variant, the yield of the Belvedere variety was 3.41 t/ha, while in the Sumatra variety it was 3.58 t/ha. With the application of the herbicide Promex, the yield increased to 3.73–3.94 t/ha, and in the Promex + Proxanil variant, it was 4.05 t/ha (Belvedere) and 4.28 t/ha (Sumatra), which was 18.8 % and 19.6 % higher than the control, respectively. The increase in yield was accompanied by an increase in the oil content in the seeds. In the control, the oil content was 47.2 % (Belvedere) and 48.0 % (Sumatra), while with the combined application of herbicides it was 49.0 % and 50.2 %, respectively. The increase in this indicator by 3.8–4.6 % indicates an improvement in the physiological state of plants, a decrease in allelopathic stress and a more efficient use of photosynthesis products. Conclusions. It was found that the Sumatra variety demonstrated higher competitiveness against weeds and consistently higher yield and oil content compared to the Belvedere variety. The most effective herbicide control measure was the combined use of herbicides Promex (2.0 l/ha) + Proxanil 72 % c. e., which provides not only a significant reduction in the number of weeds, but also an increase in crop productivity. The results obtained indicate that optimal herbicide protection allows realizing the full potential of the crop, increases the productivity and quality of sunflower seeds, making the Sumatra variety the most promising for cultivation in the western Forest-Steppe of Ukraine.