Abstract:
Muchefforts have been focused on rice allelopathy research for last three decades as
allelopathy is a sound alternative strategy to deal with weed management in paddy
ecosystem in sustainable manner. Proper studies on allelopathi potential of Sri Lankan
improved rice varieties have not been conducted so far. Plant-plant interference is the
combined effect of allelopathy and resource competition at field level. Therefore,
separation of the contribution of these two components in natural ecosystems is difficult.
~ However, it is important to evaluate relative contribution of these two components to
total bio interference to use allelopathic potential to combat weed problem. Therefore
the main objective of this experiment is to separate allelopathic effect and resource
competition of 9 commonly cultivating Sri Lankan improved rice (Oryza sativa L.)
varieties.Barnyardgrass {Echinochloa crus-galli) was used as it is one of the greatest
yield-limiting weeds in the irrigated rice systems of Sri Lanka. Rice/Banyard grass
mixed cultures and monocultures grown in residual solution of mixed cultures were used
for this experiment. Dry weight of rice and banyard grass in mixed culture and mono
culture were taken 30 days after planting. The statistical analysis was performed by
using the SAS and the mean differences were adjudged using LSD at 5% level of
probability.Results showed that the total inhibition (IP) caused by rice varieties LD 368,
LD 365 and LD 408 for plant dry weight of BYG were more than 30% in rice/BYG
mixed-cultures. However the contribution of allelopathic effect on plant dry weight
reduction of BYG was 11.4%, 15.5% and 22.8% respectively. These results demonstrate
that separation of allelopathic effect from resource competition is important when
screening genotypes for higher allelopathic potential.
