Asian Journal of Agricultural and Horticultural Research

This study aimed to determine the effective concentration of cogongrass (Imperata cylindrica) extract in inhibiting the germination, vegetative growth, and yield of cucumber (Cucumis sativus L.) test plant, and to calculate the IC₅₀ value as an indicator of its allelopathic potential. A Completely Randomized Design (CRD) was employed with five concentrations of cogongrass extract (0%, 2.5%, 5%, 7.5%, and 10%), and the experiments were conducted in both laboratory and greenhouse settings. The study took place from November 2024 to January 2025 at the Agronomy Laboratory and Medan Baru Experimental Station, Kandang Limun District, Bengkulu City, Indonesia. The study consisted of two stages. In the laboratory, 25 cucumber seeds were placed in Petri dishes containing varying extract concentrations and observed for seven days to evaluate germination and early growth. Germinated seedlings were then transplanted into a soil-manure mixture in a greenhouse to assess further growth and yield. Data were analyzed using ANOVA, followed by polynomial regression and LSD tests. The IC₅₀ values were calculated to assess the allelopathic strength of the extract. The extract significantly reduced germination rate, radicle and plumule length, and seedling dry biomass. The lowest IC₅₀ value was found for abnormal seedling percentage (6.33%), indicating high sensitivity of cucumber to cogongrass allelochemicals. In the greenhouse, the 10% extract significantly reduced plant height, leaf number, root and shoot biomass, leaf greenness, and yield. Cogongrass exhibited strong allelopathic effects on cucumber, even at low concentrations. Compounds such as phenols, flavonoids, and alkaloids are suspected to be the primary agents disrupting plant physiological processes. These findings suggest cogongrass has potential as a natural bioherbicide for sustainable weed management.