Combined laboratory and field evaluation of aqueous plant extracts identifies field weed extract as a potential biostimulant for maize growth and productivity

Abstract The search for sustainable plant biostimulants has increased interest in allelopathic plant extracts as environmentally friendly alternatives for improving crop productivity. This study evaluated the allelopathic effects of aqueous extracts from Fabaceae , Poaceae and Brassicaceae species on early maize development under laboratory conditions and assessed the agronomic potential of the most promising extract under field conditions. Laboratory experiments examined seed germination, seedling height, root length and fresh biomass at three extract concentrations (1:250, 1:50 and 1:10). Botanical families differed markedly in their biological activity. Brassicaceae extracts exhibited the strongest inhibitory effects, reducing germination by up to 49.7% points and root length by 69%, whereas Poaceae extracts produced only minor, species-dependent responses. Fabaceae extracts showed the greatest variability, ranging from pronounced stimulation to severe inhibition. Among all treatments, field weed extract consistently promoted maize germination, shoot elongation and root growth without reducing seedling biomass. Based on these responses, field weed extract was selected for field evaluation. Application of the 1:50 concentration increased cob density by 64.6% and grain yield by 54.3% compared with the untreated control, while the 1:10 concentration increased grain protein content by 13.8% and reduced crude fibre by 20.1%. The findings indicate that combined laboratory screening and field evaluation can be useful for identifying plant-derived extracts with potential agronomic value.