The relationship between the establishment of seedling directly sown on well-drained paddy field and reduction condition and/or temperature was investigated without coated calcium peroxide. The experiment was conducted in an incubation box under two different temperature conditions (15 and 17℃) and two moisture conditions (flooded and unflooded) under lighted conditions. There were four plots, i.e. high temperature and flooded plot (HTF), low temperature and flooded plot (LTF), high temperature and unflooded plot (HTU), and low temperature and unflooded plot (control, C). Change of the conditions (15 to 17℃ and/or unflooded to flooded) was carried out in 3-d intervals from 0 d after sowing (DAS). Emergence percentage (number of emerged seedlings/number of seeds sown), establishment percentage A (number of established seedlings/number of seed sown) and establishment percentage B (number of established seedlings/number of emerged seedlings) were elucidated. 1) The earlier the change of conditions, the lower the emergence and establishment percentages were observed in HTF as compared with HTU. Higher emergence and establishment percentages were obtained in HTF than LTF when flooding and temperature changes were conducted before 15 DAS. 2) Effect of the beginning time of flooding on establishment percentage B related on the growth stage of rice seedling. Establishment percentage B was divided into 3 groups by the beginning time of flooding, i.e. the lowest was 0 to 3 DAS, medium was 6 to 12 DAS and the highest was 15 to 21 DAS. 3) Consequently, the time after emergence of seedling was the suitable stage for the start time of flooding to obtain high and stable establishment of seedlings of rice plant.
