Competitive relations between weeds and corn in the process of common vegetation

Goal. To assess the competitive relationships between weed plants and maize during joint vegetation. Methods. Information-analytical methods, field and laboratory research, measurement, comparative, and mathematical-statistical methods were used. Results. It was found that at a temperature of +10°C, weed seeds germinated worse than maize seeds. Insufficient soil moisture not only reduced the growth and development of weeds, but also increased their sensitivity to herbicide action. One month after herbicide application, weeds completely dried out under low soil moisture conditions. Maize exhibited edificatory properties up to the 2-leaf phase. In maize crops, annual grass weeds predominated — Setaria glauca L. (yellow foxtail), Echinochloa crus-galli L. (barnyard grass), and annual dicotyledonous weeds — Barbarea vulgaris R. Br. (yellow rocket), Ambrosia artemisiifolia L. (common ragweed), and Portulaca oleracea L. (common purslane). Their numbers in 70 cm row spacing during the 5—7 leaf phase were 121.0, 17.5, 8.5, 13.5, and 16 plants/m², respectively. The number of other weed species ranged from 0.5 to 4.5 plants/m². In plots with 50 cm row spacing, the number of dominant weed species was noticeably lower, likely due to a smaller feeding area and denser shading of the interrow space by the crop. Row spacing width also affected plant height, leaf area, and aboveground biomass accumulation. A significant competition for water resources was recorded: soil moisture in weed-infested areas decreased by 9.4%, 38.5%, and 5.2% at the beginning, middle, and end of the growing season, respectively. The phytocoenotic pressure of weeds on the crop led to a 2.7-fold decrease in maize yield at 70 cm row spacing and a 3.0-fold decrease at 50 cm spacing. The competitiveness index of maize was on average 62.3% at 70 cm and 66.7% at 50 cm row spacing. Conclusions. Air temperature, soil moisture, and row spacing width had a significant effect on the competitive relationships between weed and maize plants during ontogenesis. These interactions influenced plant growth and development. It was found that under unfavorable environmental conditions, weed seeds germinated worse than maize seeds. Reducing row spacing in maize crops enhanced the crop’s competitiveness, which was reflected in a lower number of dominant weed species and increased vegetative mass. It was proven that weeds are an active source of water consumption in the agrocenosis: on weed-infested plots, soil moisture decreased on average by 23.5% during the growing season. Joint vegetation of weeds and maize reduced maize yield by 2.7 to 3.0 times during the years of research.