Evaluation of allelopathic potential of plant extracts against common weed species under vivo conditions

Weeds severely reduce crop productivity by competing for essential growth resources while increasing herbicide resistance and environmental risks associated with synthetic chemicals necessitate the development of eco-friendly alternatives. This study evaluated the allelopathic potential of different plant-based extracts, including walnut ( Juglans nigra ) bark, sugarcane ( Saccharum officinarum ) bagasse, Prthenium ( Parthenium hysterophorus) , Tumha ( Citrullus colocynthis) , algal water extract, Dumbi Citti ( Phalaris minor commonly called little seed canary grass ) leaf extract, vinegar and tap water (control), against six problematic weed species: Phalaris minor , Melilotus indicus , Cirsium discolor , Cucumis pubescens , Cyperus rotundus and Convolvulus arvensis . The experiment was conducted under controlled conditions using a completely randomized design with five replications. The results showed that treatments significantly ( p ≤ 0.05) affected germination, germination energy, chlorophyll content, shoot and root growth and biomass accumulation of weed species. Walnut bark, algal water and vinegar exhibited the strongest inhibitory effects across most parameters. Cirsium discolor and Cucumis pubescens were the most sensitive species, with minimum germination ranging from 0.30% to 0.53%, whereas Phalaris minor showed the utmost tolerance, with maximum germination (79.25%). Sugarcane bagasse and Parthenium hysterophorus showed moderate suppression while Phalaris minor extract exhibited limited autotoxic effects. Maximum chlorophyl content (37.60 SPAD value) recorded in control and in Phalaris minor . Highest SPAD value of Phalaris minor reflected on roots and shoot length (cm) of this six weeds. Overall findings indicate that plant-derived water extracts particularly walnut bark, algal water and vinegar, possess strong bio-herbicidal potential and may serve as sustainable alternatives for weed management. However, their effectiveness varies among weed species and higher concentrations or integrated strategies with reduced herbicide use may be required for managing highly resistant weeds such as Phalaris minor and Cyperus rotundus .