Weed Control Efficacy of Sorghum Shoot Extract Extracted with Various Solvents

The application of allelopathy in sustainable agriculture was suggested as an environmentally friendly tool to manage weed infestation. This study aims to determine the phenolic compounds in the sorghum shoot extracts by liquid:liquid extraction using various solvents (ethanol, ethanol–chloroform, ethanol–hexane, ethanol–ethyl acetate, and ethanol–methylene chloride) and to assess weed control efficacy of the sorghum extracts. Analysis of the phenolic compounds indicated that ethanol–ethyl acetate fraction contained highest phenolic compounds. Bioassay using four weed species, Abutilon avicennae, Digitaria sanguinalis, Amaranthus retroflexu, and Echinochloa crus–galli indicated that the extracts significantly inhibited the germination and growth of four weed species. In addition, the sorghum extracts had post–emergence activity for the weed species. Based on field studies, the sorghum shoot extract at 1 g/mL concentration and three times of applications at 7, 14, and 21 days after tillage controlled weeds more than 90% of untreated control. Based on the high herbicidal efficacy of the sorghum shoot extract extracted with ethanol–ethyl acetate, the sorghum extract is a promising material and might be used as a natural herbicide in the organic farming system.