Weeds in sweet corn reduce the yield and are economically more harmful than other pests. The aim of this study was to evaluate the effects of mechanical weed control and efficacy of pre- and postemergence applied herbicides in sweet corn, and their influence on weed control expressed by various indices, corncob yield and net return. Field studies were carried out with preemergence thiencarbazone-methyl + isoxaflutole (at 29.7 + 74.3 g · ha ^–1), postemergence S-metolachlor + terbuthylazine (937.5 + 562.5 g · ha ^–1), mesotrione + terbuthylazine (100 + 652 g · ha ^–1), terbuthylazine + mesotrione + S-metolachlor (656.3 + + 131.3 + 1093.8 g · ha ^–1), weed free (WF, hand weeding), and mechanical weeding (MW, hoeing) to assess weed control, corncob yield and net return. Variability in potential yield losses was observed between years due to weather conditions at the level of 30 to even 93%. Hand weeding was the most effective, but it is expensive and needs is labour consuming, unlike mechanical weeding which was the cheapest but simultaneously the least effective. Among pre- and postemergence applied herbicides, a mixture of terbuthylazine + mesotrione + S-metolachlor was the most efficacious weed control treatment. It gave high corncob yield and economic net return.

Sorghum produces allelopathic compounds, including total phenolic compounds and sorgoleone, which exhibit a phytotoxic effect on weeds. The field study, carried out in 2016-2017, was designed as an one-factor experiment, in the randomized block design, in four replications, with Sucrosorgo 506, Rona 1, KWS Freya, KWS Juno, and KWS Sammos, to assess the impact of allelochemicals on weeds. Weed infestation was determined at the beginning of July. Individual weed species were collected from two random places in each plot and weighed. The aim of the laboratory study was to evaluate the total content of phenolic compounds, and sorgoleone in the early stages of plant development (5, 10, and 15 days after emergence) in varieties Rona 1, KWS Freya, KWS Juno, KWS Sammos, Farmsorgo 180, GK Aron, PR 845F, Sucrosorgo 506 and PR849F. The total content of phenolic compounds was determined using the colorimetric method, and the sorgoleone HPLC technique on a Flexar chromatographic set. The highest value of sorgoleone was observed in 15-day-old seedlings of KWS Juno, the lowest in 5-day-old seedlings of Sucrosorgo 506, the highest levels of total phenolic compounds in 5-day-old seedlings of PR 845F, the lowest in 15-day-old seedlings of Farmsorgo 180. The results do not fully confirm the beneficial effect of allelopathic compounds on reducing weed infestation, however, it is important to emphasize the diversity of cultivars used. The statistically insignificant results indicated that most varieties of sorghum plants do not exhibit a significant decrease in yield.

Weeds in sugar beet ( Beta vulgaris L.) can contribute to a significant reduction in the root yield. The species composition of these plants is an important factor influencing the competition with crops. The aim of the 2-year field experiment with mixtures of: phenmedipham + ethofumesate + metamitron + quinmerac; ethofumesate + metamitron + metamitron + + quinmerac + triflusulfuron-methyl; phenmedipham + ethofumesate + metamitron + + quinmerac + triflusulfuron-methyl + clopyralid + lenacil, and phenmedipham + ethofumesate + metamitron + quinmerac + triflusulfuron-methyl + clopyralid applied in split doses, microdoses and Conviso Smart technology was to determine the weed species community composition and effectiveness of weed control strategies. The most common species occurring in both years were: Chenopodium album L., Fallopia convolvulus L., and Geranium pusillum L. The communities had the highest values of biodiversity indices in 2020 and lower values in 2021. There were no statistically significant differences in the herbicidal effectiveness of the tested herbicidal technologies over both years of research and for individual main weed species – 95–99%. The use of all herbicide variants contributed to achieving significantly higher yields than untreated treatments, and contributed to an increase in profitability of cultivation, but this result depended on the selected strategy. The presented herbicide solutions were characterized by direct income at a similar level.