Screening of allelopathic activity of common weed species occurring in agricultural fields

The investigation of allelopathic effects of different plant species is important to prevent serious crop losses that would arise. The usage of such materials as mulch, cover crops or residues will be useful to implement in integrated weed management strategies of agricultural fields. Therefore, this study was conducted to screen the allelopathic effect of selected plant species using seedlings growth of lettuce (Lactuca sativa L.) as an indicator. The sandwich method was used and 20 mg of dried plant material, resembling the leaf litter, from 27 species were placed in petri dishes. Twenty-eight treatments including the control treatment were arranged in a Completely Randomized Design (CRD). On the fifth day after the establishment of lettuce seeds, hypocotyl length (cm), radicle length (cm) and total height (cm) of seedlings were measured. The inhibitory percentage was calculated and a dendrogram with single linkage was developed. Results revealed that the lowest hypocotyl and radicle lengths with the highest inhibitory percentage were recorded for Ageratum conyzoides, Cassia occidentals and Clidemia hirta when compared to the control treatment (p<0.05). Weed species expressed varying degree of inhibitory effects on growth performances of lettuce seedlings. Further studies need to be carried out to explore the effects of allelopathy on crop plants. Key words: Inhibitory percentage, lettuce, seedling growth, hypocotyl, radicle.