Effects of Different Sowing Date on Yield of Late-maturing Middle Japonica Rice Yang 20238

[Objective] The study was to seek the suitable sowing date of middle japonica rice Yang 20238.[Method] In the field test with 6 sowing dates(May 8, 15,22 and 29,June 5 and 12)the leaf age,initial heading stage,plant height,yield per plant and yield components were investigated to analyze the effect of different sowing dates on the characters investigated.[Result] During May 8 to June 12,the leaves number on main stem was decreased and the duration from seeding to heading was shortened with the delaying of sowing date.The yield per plant in different sowing dates had extremely significant difference,the average yield per plant sowed on May 8 was the highest(27.9 g),and it was gradually decreased with the delaying of sowing date.The effective panicle number per plant had significant difference and the grain number per spike had extremely significant difference in different sowing dates and they got more when Yang 20238 was sowed on May 8 being 8.2 and 140.7 resp.The seed setting rate and 1 000-seed weight were also gradually decreased with the delaying of sowing date.[Conclusion] The suitable sowing date for middle japonica rice Yang 20238 was the first ten days on May.