Abstract
Field trials were conducted to study the stability, growth and yield characteristics of various establishment-type cultivars of rice broadcasted in submerged soil. Rice cultivars Dontokoi, Koshihikari and Yamahikari were used. Germinated seeds were coated with calcium peroxide and were broadcasted in the submerged soil in the early May in 1999, 2000 and 2001. Establishment of the seedlings was classified into four types at the 3rd leaf stage according to the penetration and fixation of the root into the ground as follows : (1) perfect establishment type (PE type), (2) fixed type : the seedling fixed although a part of roots emerged on the ground (FX type), (3) floating 1 type : the seedling fixed although the seed was floating (FL-1 type), and (4) floating 2 type : the seedling was floating (FL-2 type). The plant length, total dry matter weight and seedling strength (shoot dry-matter weight/plant length) at the early growth stage tended to be smaller in FL-1 and FL-2 types in each cultivar. There was no significant difference in plant length among the four types after the maximum tiller number stage. Contrarily, the total dry matter weight and stem number per plant of FL-1 and FL-2 types were lower than those of PE and FX types. The low yield of FL-1 and FL-2 types was mainly attributed to a small number of spikelets per plant with a small number of panicles per plant. Besides, there were no distinct differences in 1000-grain-weight and percentage of ripened grains among the four types at harvest. As described above, the insufficient fixation of root into the ground at the 3rd leaf stage decreased stem number, which accounted for the small number of panicles and the low yield.
