• KOREAN JOURNAL OF CROP SCIENCE
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• v.39 no.5
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• pp.405-411
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• 1994

This study was carried out to determined the optimum seeding rate and number of seedling stands per unit area for high yield with two varieties of rice, Nakdongbyeo (Japonica type) and Samgangbyeo (Indica x Japonica type), in direct water-seeded rice culture at Crop Experiment Station. Seeds coated with $CaO_2$ after germination were sowed at May 4 in 7 levels, such as 1.6, 1.8, 2.1, 2.7, 3.5, 4.0, 4.3kg /10a, and the number of seedling stands per square meter was adjusted to be 30, 40, 60, 80, 100, 120, 140 plants, respectively. The maximum number of tillers increased as the seeding rates increased, but the ratio of effective tillers decreased. The critical dates of effective tillering of tested varieties were delayed by the lower seeding rates, and the date was June 18 at the plot of seeding rate with 3.5kg /10a. The number of panicles per unit area increased in accordance with the increased seeding rates. The number of spikelets per panicle in Nakdongbyeo was not affected by the seeding rates, but in Samgangbyeo it decreased as the seeding rate increased. The optimum number of seedling stand per square meter appeared to be 78 in Nakdongbyeo and 120 in Samgangbyeo, respectively. It meant that the optimum seeding rates for Nakdongbyeo and Samgangbyeo were about 2.7 and 4.0kg /10a, respectively.