Preliminary Study on the Biology and Ecology Characteristic of Direct Sowing Rice Optimal Seeding Stages

Using the method of correlation analysis to analyze different seeding data of direct sowing rice,the results showed that the relation between rice yield and seeding date in Shanghai area is the parabola type,and optimal seeding time of direct sowing rice in Shanghai region is on 13 June.The best effective panicle number under the best seeding date is 360×104 hm-2,with 105 grains on per panicle,11%～12% of unfilled-grains rate,25 g of 1000-grain weight,43%～44% of economic coefficient,and 150 days during the whole growing season.The correlation coefficient between yield and the leaf area index of the peak period of tiller,dry matter weight of leaf are-0.8957(P0.05) and-0.9928(P0.01),respectively.The correlation coefficient that yield and leaf area index,dry matter weight during heading to maturity are 0.8505 (P0.1) and 0.8130(P0.1),respectively.During the tiller period and higher tiller period,sunshine duration are higher than 70 h,the effective panicle number obviously increases.When sunshine duration between initial panicle formation to cell division is lower than 160 h,total grains obviously decreases.When the minimum air temperature while blooming is lower than 18℃,the rate of unfilled grain reaches above 18%.Average minimum air temperature before and after heading is lower than 23℃ or sunshine duration is lower than 200 h,1000-grain weight is lower than 23 g.