Growth of Echinochloa glabrescens in Response to Rice Cultivar and Density

Abstract

In Asia, Echinochloa glabrescens is one of the most common Echinochloa species in rice production systems. The use of weed-competitive rice (Oryza sativa L.) cultivars and rice density are important components of integrated weed management tools, but their use requires understanding the extent to which rice can interfere with E. glabrescens growth and how the weed may respond to this interference. Growth of E. glabrescens was studied in a screenhouse by growing it alone and with 4, 8, and 16 plants of two rice cultivars (Rc222 and Sabita). Sabita was taller than Rc222, but Rc222 had greater biomass than Sabita. E. glabrescens produced greater shoot biomass and seeds plant−1 when grown with Sabita than with Rc222. Increases in rice density progressively reduced the number of leaves, leaf area, shoot biomass, and seed production of E. glabrescens. However, E. glabrescens grown with the highest rice density responded with increased leaf weight ratio, leaf area ratio, and specific stem length. Despite such plasticity, E. glabrescens shoot biomass and seed production decreased by 83% and 88%, respectively, when grown with 16 rice plants (approximately 80 kg seed ha−1) compared with its biomass and seed production without crop interference. The results suggest that rice interference alone may significantly reduce the growth of E. glabrescens but may not provide complete control. This highlights the need to integrate different weed management strategies to achieve complete control of E. glabrescens and other weeds in direct-seeded rice systems.