Separation of Allelopathic Effect from Resource Competition of Sri Lankan Improved Rice {O ryza sativa) Varieties on Growth of Barnyard grass (E chinochloa crus-galli L)

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.