Allelopathic potential of plant residues of thirty Sri Lankan traditional rice (Oryza sativa L.) varieties on Barnyardgrass (Echinochloa crusgalli)

The use of rice (Oryza sativa L.) allelopathy for weed management could reduce the need for applying herbicides to the crop. In this study a pot experiment and a laboratory bioassay were conducted to assess the allelopathic potential of residues of 30 traditional rice varieties in Sri Lanka on seed germination and seedling growth of barnyardgrass (Echinochloa crus-galli). All seeds were collected from “Farmer Federation for Conservation of Traditional Seeds and Agri Resources”. Rice residues were incorporated with silica sand (1% w/w) in small pots to prepare residue mixture and ground rice residues mixed with water (2.5g/100ml) were used to prepare residue extract for laboratory bioassay. Rice varieties exhibited marked differences in the inhibition of barnyardgrass growth and development. In the bioassay, residue extract of rice variety Herathbanda exhibited the greatest activity on the weed seedling growth, reducing dry weight by 30.7%, while Gonabaru residue extract exhibited the greatest inhibition on seed germination, reducing germination by 29.6%. In the pot experiment of residue mixture, Batapola el and Sula varieties showed the greatest inhibition percentage on germination (48.4%). However, Godaheenati showed the greatest inhibition % on plant height (27.4%) and dry weight (45.6%). These results suggest that incorporation of rice residues of tested varieties has influence on controlling barnyardgrass seedling growth.