Effects of Rice Sowing Date on Floret Degeneration and Yield

[Objective]The aim was to research the suitable sowing date of two new rice varieties,Yongyou 12 and Zheyou 18.[Method]The influence of six sowing dates on rice floret degeneration and yield was investigated.[Result]The results showed that the initial heading stage,full heading stage and mature stage of Yongyou 12 and Zheyou 18 were delayed with the prolonging of sowing date,and the whole growth periods shortened. Simultaneously,the floret degeneration rate first increased and then decreased with the prolonging of sowing date. Different sowing dates affected yield component factors,including effective panicle number and thousand grain weight. The highest yields of both Yongyou 12 and Zheyou18 were sowing on May 10th,followed by sowing on May 25th,and then the yield was suddenly decreased.[Conclusion]The most suitable sowing date in Quzhou region of both Yongyou 12 and Zheyou 18 was at the middle of May.