Seedling establishment of direct seeded rice without coating of oxygen-generator on the soil surface in flooded paddy fields

This study was conducted to clarify seedling establishment of direct seeded rice without coating of oxygen-generator, water temperture and dissolved o xygen conditions on the soil surface in flooded paddy fields [FPF] at north ern Kyushu for development of low cost and labor saving production. The mea n water temperature a day during 14 days after seeding ranged from 21.8 to 29.0 degreesC. On the other hand,the mean diurnal dissolved oxygen content in flooded water ranged from 4.7 to 11.6 mgL(-1), which were high enough fo r germination and rooting of rice seeds. Eemergence percentage in FPF varie d from 0% to 89% among 72 varieties. There were I I varieties with more tha n 80% of emergence percentage. Eight varieties of them had a ancestor 'Asah i'. The floating seedling rate + turned down seedling rate in FPF varied fr om 4% to 64% among 65 varieties of which had emergence percentage was 10% o ver. There was no significant correlation between emergence percentage and floating seedling rate + turned down seedling rate among the I I rice varie ties with high emergence percentage rate. Therefore, there were rice cultiv ars that were superior in emergence of 80% over and floating seedling rate + turned down seedling rate of 10% less (i.e., Shinriki, Haenuki and Domann aka). High emergence percentage varieties had heavy grains, high bulk densi ty of 1.1 over. Low floating seedling rate + turned down seedling rate vari eties had high bulk density of 1.1 over and grown seminal root slowly. Thes e results were helpful to select and breed varieties with good emergence an d establishment in direct seeded rice without coating of oxygen- generator on the soil surface in flooded paddy field.