Allelopathic Screening of Several Weed Species as Potential Bioherbicides

Abstract Many plants that are considered to be weeds have the potential to exhibit allelopathy; they might therefore be used as a herbicides to control other weeds. The aim of this study was to identify the best potential bioherbicide against spiny Amaranthus spinosus growth at various concentrations from among five weed species: Imperata cylindrica, Cyperus rotundus, Chromolaena odorata, Ageratum conyzoides, and Axonopus compressus. The study followed a non-factorial, completely randomized design, examining 17 treatments with three replicates. Extracts of the leaves, tuber, and/or rhizome of the five sample plants were obtained using maceration and were applied to the indicator weed A. spinosus at concentrations of 10%, 20% and 30%. A synthetic herbicide (2,4-dichlorophenoxyacetic acid at 0.686 kg/ha) was used as a positive control and distilled water as a negative control. The application of allelopathic extracts of the weeds at various concentrations significantly affected the height growth rate, the percentage of weed control, leaf area, root length, and shoot and root dry weight growth of A. spinosus. The greatest inhibition on A. spinosus growth at 7 days after application was observed with a 20% concentration of A. conyzoides, followed by 20% concentrations of C. rotundus, C. odorata.