Impact of water stress and sorghum varieties on flavonoid content and the bioherbicidal potential of water extracts for weed control

The results showed that the Super 1 sorghum variety under drought stress with watering every 4 days produced the highest total flavonoid content (4120.61 µg/g), while the Bioguma variety with watering every 2 days had the lowest total flavonoid content (2859.83 µg/g). A longer drought stress period led to the higher the flavonoid content. The allelopathic extract sources showed varying levels of effectiveness in inhibiting weed growth. Sorghum aqueous extracts (based on variety and drought stress level) were able to control grass weeds, except Eleusine indica, which showed higher tolerance. Sedge was effectively suppressed by extracts from the Super 1 variety under 4- or 5-day stress intervals and the Suri 4 variety with 5-day stress. Broadleaf weeds were effectively controlled by extracts from the Super 1 variety under 4-day drought stress. Sorghum aqueous extracts effectively controlled weeds, with weed control efficiency ranging from 69.19% to 77.52%. The highest weed control efficiency (77.52%) was achieved using extracts from Super 1 under 5-day drought stress and Suri 4 under 4-day stress. Consequently, sorghum aqueous extract can be considered a possible bioherbicide for efficient weed management. To identify the most effective allelopathic constituents for weed management, additional experiments with extracts from different sorghum varieties subjected to greater drought stress (beyond 5 days) will be needed.