Stewart Runsick, C.E. Wilson Jr., D.L. Frizzell, and J. Hill. Univ. of Arkansas, 208 1/2 Main Street, Newport, AR 72112
Optimum seeding rates are important for uniform stand establishment in drill-seeded rice (Oryza sativa, L.) production. However, over-compensation for potential problems associated with establishing and maintaining an optimum stand can result in overpopulation. Excessive stand densities result in increased disease pressure, increased competition among rice plants, and increased lodging. Therefore, finding the optimum rate allows for reduced risk from overpopulation but allows minimizes risk of insufficient stand density. Previous research conducted during the 1970’s suggest an optimum seeding rate of 430 seeds/m2 was needed to obtain a final target stand density of 160 to 215 plants/m2. However, this work was conducted using taller statured cultivars. Little research has been conducted to evaluate the optimum seeding rates for the shorter-statured cultivars currently grown in the Southern USA rice belt. The general hypothesis is that many producers plant excessively high seeding rates and reduced seeding rates can be utilized to decrease lodging, disease pressure, and input costs, and still maintain high yields. Therefore, the objective of the study was to determine the optimum seeding rate for five commercially-produced rice cultivars in a drill-seeded cultural system. Field studies were established in 2004, 2005 and 2006 in Chicot, Poinsett, Prairie and Woodruff counties to evaluate grain yield and milling yield of five modern rice cultivars (‘Wells’, ‘Francis’, ‘CL 161’, ‘Bengal’ and ‘Medark’) at five seeding rates under various field conditions. Each cultivar was seeded at rates of 50.4, 75.6, 100.8, 126, and 151.2 kg/ha in 7.6 m-long plots in 8 rows on 18-cm row spacings. Grain yields were not different when comparing the currently recommended seeding rate of 100.8 kg/ha to 75.6 kg/ha for any of the cultivars evaluated. Consistent across all locations and years, a seeding rate of 75.6 kg/ha achieved optimum stand density and maintained grain yields.
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