Abstract:
Weedy rice (Oryza sativa), a weedy relative of cultivated rice, is an emerging weed problem
in many rice-growing areas in Sri Lanka. Weed-crop competition is one of the major
causes of the yield loss of crops, and competition between crops and weed populations is
often affected by many factors, including cultivation methods and weed densities. Limited
information is available on the rice cultivation methods and different weedy rice densities
on the growth of cultivated rice. A study was conducted to determine the impact of weedy
rice populations on the growth of direct-seeded and transplanted rice. A random two-factor
design was used in' this experiment. Factor one (the cultivation methods) included two
levels: direct-seeding and transplanting. Factor two (the density of weedy rice) included
four levels: o, 6, 12, and 24 weedy rice individuals per m2. As a result, eight treatments
were designed for the experiment. Each treatment contained three replications that were
arranged in randomized complete block design in a field layout. Plant height and number
of tillers per plant were recorded at seedling and heading stage. Two-way ANOVA tests
were performed for measured characteristics. Rice plant height and number of tillers were
not affected by the interactions between different factors; however, it was significantly
influenced by rice cultivation method and weedy rice density. Plant height and number
of tillers were higher in transplanted plots than direct-seeded plots in both seedling
and heading stages. Weedy rice density Significantly affected the height and number of
tillers of cultivated rice. Cultivated rice plants grown without weedy rice interference had
a significantly highest number of tillers and plant height and they were declined with
increases in weedy rice density. The cultivated rice showed less competitive ability in the
direct-seeded plots than in the transplanted plots.
