Competitiveness of swamp rice against Echinochloa crus-galli and Monochoria vaginalis weeds

Weed competition, especially with Echinochloa crus-galli and Monochoria vaginalis, is a major constraint in rice production as they reduce yield by competing with crops for resources such as light, nutrients, and water. Therefore, this study aims to determine rice competitiveness against Echinochloa crus-galli and Monochoria vaginalis weeds. The experimental design was a split-plot with four replications, with the main plot being weed-free, E. crus-galli, and M. vaginalis treatments, while the subplot was rice varieties namely Inpara 3, 4, 7, and 8. The result showed that existence of weeds reduced the plant height, tillers, photosynthetic rate, leaf area, biomass, percentage of filled grain, and yield of rice due to competition, with losses up to 15%. Furthermore, the rice varieties differed in their yield performances and weed competitiveness. The grain yield ranged from 7.75 t ha-1 to 5.96 t ha-1 for Inpara 4 and 8, respectively, under the weed-free condition. A low weed tolerance and suppress ability was found in Inpara 7, both for E. crus-galli and M. vaginalis. Inpara 8 had a low weed tolerance in E. crus-galli, but high in M. vaginalis, while Inpara 4 produced the highest yield in a weedy condition, along with high weed tolerance and suppress ability. Traits related to the leaf area and rice dry weight at grain filling stage are associated with rice competitiveness. Based on the results, competitive rice can be an important strategy for reducing hand weeding and herbicide inputs in rice production.