| The experiment was conducted in the Diaoyu town of Xinghua City from 2017 to 2019.Under the annual cultivation for rice and wheat,rice was planted with late maturing medium japonica Nanjing 9108 and medium maturing medium japonica Lianjing 11 as materials.Five sowing dates were set:May 22(R1),May 29(R2),June 5(R3),June 12(R4),June 19(R5).The density was set as:the first three sowing dates were 3 seedlings per hole(D3),4 seedlings per hole(D4),5 seedlings per hole(D5),and the last two sowing dates were 4 seedlings per hole(D4)5 seedlings per point(D5)and 6 seedlings per point(D6).In the wheat season,Ningmai 13 was used as the material,and four sowing dates were set:November 5(W1),November 15(W2),November 25(W3),December 5(W4).Each sowing date density is set as 300×104 hm-2 and 450×104 hm-2.In this experiment,the variation of sowing date and density on Rice Yield and composition,utilization of temperature and illumination resources,production of photosynthetic matter,rice quality and annual production of rice and wheat were studied,and the characteristics of rice varieties with high yield and high quality and high efficiency under mechanized production conditions in the lower Yangtze-huai valleys were clarified,In order to improve the utilization efficiency of illumination and temperature resources of rice-wheat double cropping system,to solve the problems such as unreasonable annual collocation of existing rice wheat varieties in the lower Yangtze-huai valleys and sharp contradiction between rice wheat cropping stubble,and to make theoretical and data support.The main results are as follows:(1)With the delay of sowing time,the growth period of rice varieties was delayed.Lianjing 11 can mature safely in five sowing dates,while Nanjing 9108,R4 and R5 sowing date cannot mature completely due to the limitation of wheat stubble.With the delay of sowing date,the whole growth period of all kinds of rice varieties was shortened obviously,which was mainly manifested in the shortening of sowing jointing period.In terms of temperature and illumination resources,with the delay of sowing date,the accumulated temperature,radiation amount and utilization rate of temperature and light of all types of rice showed a significant downward trend,and the temperature and illumination resources intercepted by late maturing mid japonica varieties were higher than that of mid maturing mid japonica varieties.With the delay of sowing date,the daily average temperature of sowing jointing stage increased significantly,and after jointing stage decreased significantly.(2)Sowing date and density had significant effect on Rice Yield and yield components.Under the same density,with the delay of sowing date,the yield of late maturing mid japonica varieties showed a downward trend,the yield of mid maturing mid japonica varieties first increased and then decreased,and the yield of R2 was the highest;the highest yield of late maturing mid japonica varieties was obtained under the density of D4,the highest yield of R1,R2 and R3 was obtained under the density of D4,and the highest yield of R4 and R5 was obtained under the density of D5.The yield components were different with the delay of sowing date,which mainly showed the decrease of spikelets per panicle and seed setting rate per ear.With the increase of density,the spikelets per panicle and seed setting rate decreased,the number of panicles increased and there was no significant difference in 1000 grain weight.(3)With the delay of sowing date,the number of tillers decreased slightly,and the percentage of productive tiller decreased significantly;with the increase of density,the number of tillers increased,but the percentage of productive tiller decreased.The dry matter accumulation,leaf area index and photosynthetic potential of rice decreased with the delay of sowing date and increased with the increase of density;the dry matter accumulation.population growth rate and net assimilation rate of rice in heading maturity stage showed the similar law with the yield change.(4)With sowing date delayed,the milling quality for Nanjing 9108(LRMJ)became better and the appearance quality became worse,but for Lianjing11 the milling quality became worse and the appearance quality became better,and the cooking and eating quality and nutritional quality except the taste value for Lianjing 11 became worse gradually.The characteristic value of RVA spectrum of the two varieties deteriorated with the delay of sowing date.In terms of density,with the increase of density,the protein content of rice increased slightly,the nutritional quality became better,the processing quality,appearance quality,cooking and eating quality,and the RVA spectrum characteristic value of rice showed a trend of deterioration.(5)From the perspective of annual production,the annual yield of rice and wheat decreased significantly with the delay of the rice and wheat sowing date,and reach maximum yield under combination of R-I and W-Ifor Nanjing9108-ningmai 13.The highest ratio of rice yield to annual yield was 62.99%,and the lowest was 55.86%.The maximum distribution rate of accumulated temperature between two seasons was 68.38%in rice season and 34.14%in wheat season,and average distribution rate of radiation between two seasons was 51.7%in rice season and 48.3%in wheat season.The downward trend was found in both annual accumulated temperature production efficiency and radiation production efficiency with the delay of sowing dates of rice and wheat season,and the later the sowing date,the more significant the reduction. |
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