Rice Yield Components as Affected by Cultivar and Seeding Rate

Received for publication April 26, 2005. New rice (Oryza sativa L.) cultivars have been released that possess yield potential >10000 kg ha^-1. Some of these new cultivars have increased costs associated with them due to patented input traits and/or hybrid technology. Research analyzing the effects of seeding rate on yield components with modern cultivars is not well-documented. Therefore, field trials were conducted near Stuttgart, AR, in 2002 through 2004 with the objective of determining the effect of rice seeding rate on yield components of three modern, long-grain rice cultivars. This research was done in an effort to determine if lower-than-recommended seeding rates would produce yields similar to currently recommended rates. Rice seeding rates from 57 to 500 seeds m^-2 resulting in a rice density range of 73 to 373 plants m^-2 did not effect rice aboveground biomass production, panicle density, harvest index (HI), or rice yield, regardless of cultivar. ʹWellsʹ produced higher panicle weights and had a higher HI than ʹCL161ʹ across the range of rice densities. Cultivars XL8 and Wells produced similar yields, and these yields were higher than CL161. Cultivar, rice density, and thermal time were significant factors affecting rice canopy coverage. Cultivar XL8 achieved canopy coverage sooner than CL161 or Wells. As rice density increased, canopy coverage increased by 3% for every additional 100 plants m^-2. As degree days (DD50) accumulated, canopy coverage increased 0.4% °Cd^-1. Results from this study indicate that recommended seeding rates for CL161, Wells, and XL8 can be reduced while maintaining similar yields.