Effect of Weedy Rice Density on Tillering and Plant Height of Direct-seeded and Transplanted Rice

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.