Effects Of Sowing Dates On Yield Formation Of Ratooning Rice

In order to explore the effects of different sowing dates on growth,development and yield of ratooning rice,this study was carried out in Jinjing Town,Changsha City in 2019.Split zone experiment design was adopted,with seeding period as the main area,March 15th(B1)、March 20th(B2)、March 25th(B3)、March 30th(B4)、April 5th(B5)、April 10th(B6),and varieties as the secondary area,Huiliangyou898(HLY898),Yliangyou900(YLY900),Yliangyou911(YLY911).The growth period,dry matter accumulation,yield and yield composition were observed.The main results and conclusions are as follows:1.With the delay of sowing date,the time from sowing to heading stage in the first season,the total growth period of the first season and the total growth period of the annual growth period is shortened;the time from heading stage to maturity in the first season is basically unchanged;the growth period of the regeneration season is also slightly increased.With the delay of sowing date,the annual growth period is shortened by 2-4 days.The mean daily temperature before anthesis and after anthesis increase with the delay of sowing date,but the mean daily temperature and the effective accumulated temperaturein of regeneration season decreases with the delay of sowing date.2.In terms of annual yield,with the delay of sowing date,the annual yield shows a trend of increasing first and then decreasing,and the annual yield of B2 treatment is the highest.And the yield of B3 treatment is the highest at main season,10562 kg/hm~2.The yield of the regenerating season shows a peak change,in which B2 treatment is the highest,7287 kg/hm~2.In terms of varieties,the annual yield of‘HLY898’at each sowing date changed slightly and has good yield stability,while the annual yield of‘YLY911’both early sowing and late sowing will result in significant reduction of yield.In terms of yield composition,the seed setting rate and the 1000-grain weight of the first season show a peak change with the delay of sowing date,The spike number per hole and 1000-grain weight of the regenerating season show a peak change with the delay of sowing date too.3.The dry matter accumulation before anthesis shows a decreasing trend with the delay of sowing date,and B1 is the highest.The dry matter accumulation after anthesis shows an increasing trend with the delay of sowing date,and B6 is the highest.The dry matter accumulation and harvest index of regeneration season show a peak change with the delay of sowing date,and both of them are the highest in B2 treatment,and B2 treatment is significantly higher than that in B6 treatment.4.In terms of highest seedling number is B4>B2>B3>B1>B6>B5.The plant height in the regeneration season shows a single peak with the delay of sowing date,and B2treatment is the highest,which is significantly higher than the other 5 treatments.The percentage of empty stump in the regeneration season shows a single peak with the delay of sowing date,and the percentage of empty stump in B5 treatment is the highest.From the analysis of seedling capacity of regenerated season,the highest number of seedlings shows a wavy change with the delay of sowing date,and the ratio of panicle to pile shows a peak change with the postponing of sowing date,and that of B2 treatment is the highest.In central of Hunan province,B2 treatment(sowning on March 20)has strong seedling capacity,high harvest index and the highest yield in the regeneration season,the yield of the main season is also at a high level,so the annual yield is the highest.