Allelopathic potential of some Sri Lankan traditional rice (Oryza sativa L.) cultivars against Echinochloa crus-galli L.

Weeds reduce rice yield by competing with the crops for light, nutrients and moisture. This competition is aggres-sive at seedling stage of the crop. Therefore, weed management at seedling stage is important to ensure higher yield at harvesting. Number of dominant and persistent weeds can be identified in Sri Lankan rice fields. Out of them Echinochloa crus-galli L.(Barnyard grass-BYG) is identified as most troublesome weed in irrigated rice eco-systems in Sri Lanka. Weed suppressive ability of rice is widely varied with its cultivar. Therefore an experiment was conducted with an objective to evaluate allelopathic abilities of 30 Sri Lankan traditional rice varieties on growth of BYG using rice/ BYG mixed cultures in trays, double pot technique and a field experiment. RCBD De-sign was used for all these laboratory, green house and field experiments. Initially significant (p≤0.05) differences in plant height and dry weight were observed in rice/BYG mixed-cultures relative to BYG mono-cultured controls in tray experiment. Then 8 varieties which showed highest and the variety which showed lowest allelopathic po-tential in tray experiment were further tested in double pot technique and in field experiment. Similar results were observed except variety Pokkali. Among the 30 rice varieties, Masuran and Kaluheenati showed greatest inhibitory effects on BYG growth and at field experiment these values were greater than 40% for BYG dry matter accumulation. However, further experiments by extracting allelochemicals should be conducted to conclude these varieties with greater allelopathic potential.