| The experiment was conducted in experimental farm and pasture in Yangzhou University in Yangzhou City,Jiangsu Province from 2015 to 2016.Six varieties with three types of soft rice as test materials were used to study the effects of soft rice varieties Different sowing date showed that the yield,structure,growth period,Temperature and light resources,the impact of nitrogen utilization.In order to clarify the suitable sowing date of the soft rice varieties in the area and establish the supporting technology for the high yield cultivation of rice in the Yangtze River area,the paper provides theoretical support.The main test results are as follows:(1)Sowing date had a great influence on the growth period of different varieties of soft rice and the utilization of temperature and light resources.With the delay of sowing date,the growth period of rice of all varieties was delayed correspondingly.The medium mature japonica and late maturity medium japonica cultivars could be safely matured in the six sowing dates,while the mature japonica cultivars failed to fully mature in the last two sowing dates.With the delay of sowing date,the main growth period and whole growth period of all kinds of rice varieties were significantly shortened.The three types of varieties were postponed for 2-12d,1-5d and 1-4d,respectively,and the number of days of full growth was shortened 4-20d.Further analysis of its main growth stages shows that the shortening of the whole growth period is mainly the decrease of the days from sowing to jointing,while the number of days from jointing to heading to heading to maturity is relatively stable with less decrease.Within the sowing date range of this experiment,with the delay of sowing date,the extremely significant difference of accumulated temperature and light hour before heading resulted in a very significant downward trend of accumulated temperature and light hours in all varieties.The temperature and light utilization rate of all types of varieties with the sowing of postponed were significant or very significant downward trend.(2)Sowing date had significant effects on the yield of different varieties of soft rice.Within six sowing dates,the yield of different types of soft rice varieties decreased gradually with the delay of sowing date.The components of yield varied with the sowing date.The sowing date mainly affected the number of ears,The number of seed set,the seed setting rate,both showed a decreasing trend with the delay of sowing date,but had no significant effect on the 1000-grain weight.Among the three factors,the number of spikelets,the number of grains per ear and the seed setting rate were the most affected by the sowing date,The main effect of delayed sowing date is to reduce the storage capacity of direct seeding rice populations,which is also the main factor leading to the decrease of yield as the sowing date is delayed.(3)With the delay of sowing date,the nitrogen content and nitrogen accumulation rate of three types of soft-filling rice varieties in the main growth stage showed a downward trend.At different growth stages(sowing-jointing,jointing-heading,heading-Mature)nitrogen accumulation can be seen on the difference,with the delay of sowing,stage nitrogen accumulation also showed a gradual decrease in the trend.The proportion of nitrogen accumulated in sowing-jointing stage to the total nitrogen accumulation in growing stage showed an increasing trend,while the proportion of nitrogen accumulated in jointing-heading stage,heading-maturing stage and nitrogen accumulation in the whole growth stage decreased,And the highest nitrogen accumulation at jointing-heading stage and the lowest nitrogen accumulation at heading-maturity stage. |
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