Rice Seeding and Nitrogen Rate Effects on Yield and Yield Components of Two Rice Cultivars

Field research was conducted for 2 yr to investigate the relationship between rice (Oryza sativa L.) seeding rate and preflood nitrogen (N) rate utilizing long-grain rice cultivars planted into clay and silt loam soils. Rice cultivars included 'Cheniere' and 'Wells' seeded at 162, 323, and 646 seeds m -2 . Nitrogen was applied before flooding at 67, 134, and 202 kg ha -1 . No response to soil texture and no interaction between seeding rate and N rate were detected for the parameters examined. The lowest applied N rate had lower yield than the other two N rates. Rough rice yields were 7564 for 67 kg N ha, 8520 for 134 kg N ha -1 , and 9000 for 202 kg N ha -1 averaged over all cultivars, seeding rates, and soil textures. Similarly, when head rice yield was pooled across soil texture and seeding rate, head rice yield of Cheniere was independent of N rate, but head rice yield of Wells increased when the N rate was increased from 67 to 202 kg ha -1 . Panicle density responded to N rate similar to rough rice yield. Panicle density increased with seeding rate up to 418 panicles m -2 at a seeding rate of 646 seeds m -2 . Filled grain panicle -1 was highest at a seeding rate of 162 seeds m -2 . Cheniere produced more filled grain panicle -1 while Wells had a higher 1000-grain weight. Grain yield and yield components of Cheniere and Wells respond to seeding rates and N rates independently when planted into clay or silt loam soils.