| With medium-maturing medium japonica rice(Xinfeng 2hao,Xindao 18hao,and Zhendao 18hao),late-maturing medium japonica conventional rice(Wuyunjing 24,Nanjing 9108,and Nanjing 49),late-maturing medium japonica hybrid rice(Yongyou 2640,Xinjingyou lhao,and Longyou 1875),early-maturing late japonica rice(Nanjing 44,Wuyunjing 29,and Zhendao 19),and late-maturing medium indica hybrid rice(Yliangyou lhao,Yangliangyou 6hao,and Yliangyou 2hao)as materials,setting 6 sowing date treatments(May 11th,May 16th,May 21th,May 26th,May 31th,and Jun 5th),using mechanical transplanting with carpet seedlings,the experiment was conducted in Luoshan county(Yunan rice area,32.2°N,114.5°E),Xincai county(Yuzhong rice area,33.0°N,115.1°E),and Yuanyang county(Yubei rice area,35.0°N,113.7°E)during 2012 and 2013.The effect of sowing date on traits and formation mechanism of comprehensive production capacity of different growth-period mechanical transplanting rice was comparatively studied under high-yield cultivation methods for each growth-period rice type.The temperature-light resources in different latitude areas and safe growth duration of mechanical transplanted rice in rice-wheat rotation system were taken into consideration to select the suitable growth-period rice varieties and the local representative varieties for the experiment.The traits of growth duration,temperature-light utilization,yield,dry matter accumulation and rice quality in different sowing date treatments were comparatively studied to compare and evaluate the comprehensive productivity of different types of rice under different sowing date at different latitude sites in Henan province.The results could provide the scientific basis for the rational distribution of mechanical transplanted rice in the local area.In addition,the traits and differences in fertility safety,yield,quality,and temperature-light utilization among indica and japonica rice were studied in Yunan rice area to provide scientific theory basis for“indica rice to japonica rice".The main results were as following:1.In general,the yield of different growth-period rice at Luoshan,Xincai and Yuanyang sites significantly declined with the delayed sowing date.The average yield of different types of rice were 10.68,10.63,and 10.40 t/hm2 in the I sowing date treatment,and were 7.61,7.56,and 7.04 t/hm2 in the VIsowing date treatment,respectively.Compared to I sowing date treatment,the yield of VIsowing date treatment was reduced by 3.07,3.07,and 3.36 t/hm2,respectively.Thus if the sowing date were delayed by 5 d,the average yield at Luoshan and Xincai sites were reduced by 0.61 t/hm2,and at Yuanyang site were by0.67 t/hm2.The yield of medium-maturing medium japonica rice at Luoshan and Xincai sites were highest in the II sowing date treatment and were of insignificant difference among the I and II sowing date treatments.After the II sowing date treatment,the yield was significantly declined with the delayed sowing date.The yield of late-maturing medium japonica conventional rice and late-maturing medium indica rice at Yuanyang site was highest in the I sowing date treatment and was significantly declined with the delayed sowing date.Except that the yield of late-maturing medium japonica hybrid rice at Xincai and Yuanyang sites among the I and II sowing date treatments were not significant,the yield at different sites in the I sowing date treatment were significant higher than other treatments.The yield of early-maturing late japonica at different sites were declined significantly with the postponed sowing date.With the delayed sowing date,the differences of yield among different types of rice at all sites were increased and the variable coefficient showed the same trend.In addition,the late-maturing medium japonica hybrid rice was of strong heterosis and its yieldwas larger than other types of rice in the same sowing date treatment.2.The effect of sowing date on yield components was significant.The difference in panicles per hectare were highly significant among years,sowing dates,and rice types.With the delayed sowing date,the panicles per hectare of rice were reduced.And the panicles per hectare were most for late-maturing medium japonica conventional rice(370.58×104 hm-2)and lest for late-maturing medi1m japoning hybrid rice(235.87×104hm-2).The differelces in spikelet number per panicle and total spikelets were highly significant among years,sowing dates and rice types.The spikelet number per panicle and total spikelets were significantly reduced,when the sowing date was postponed.The total spikelets in the I sowing date treatment were 1.13%,2.68%,5.56%,9.04%,and 13.26%more than ?,?,?,?,and ?sowing date treatments,respectively.In the same sowing date,both the spikelet number per panicle and total spikelets were most for late-maturing medium japonica hybrid rice.The total spikelets of late-maturing medium japonica hybrid rice were 11.83%,15.79%,19.47%,and 20.57%more than the late-maturing medium japonica conventional rice,early-maturing late japonica rice,late-maturing medium indica hybrid rice and medium-maturing medium japonica rice.The setting percentage was of insignificant difference among years,but of significant difference among sowing dates and rice types.The rice in the ? sowing date treatment was of highest setting percentage and the setting percentage were higher for medium-maturing medium japonica rice and lower for late-maturing medium japonica hybrid rice and late-maturing medium indica hybrid rice.Thus the rice with big panicle might be of low setting percentage.The 1000-grain weight was of significant difference among years,but of insignificant difference among sowing dates and rice types.With the delayed sowing date,the 1000-grain weight of all rice were significantly reduced.The 1000-grain weight was heavier for medium-maturing medium japonica rice and lighter forearly-maturing late japonica rice.For the reason that the growth duration of early-maturing late japonica rice was longer and the temperature during grain filling phase was lower,the grain filling was limited.Thus the variation of 1000-grain weight of early-maturing late japonica rice among sowing dates was bigger than other rice.The correlation analysis showed that the net contribution rate of yield components to yield was total spikelets>setting percentage>1000-grain weight,and of total spikelets components to total spikelets was spikelets per panicle>panicles per hectare.As affected by sowing dates,the main reason for the decline of yield was the reduction of spikelets per panicle and setting percentage.This study recommended that the late-maturing medium japonica hybrid rice(especially Yongyou 2640)would be a better choice in these rice areas for its bigger panicle,larger sink and higher yield potentials.On the basis of large panicle and sufficient panicles per hectare,improving the grain filling environment and increasing the setting percentage and 1000-grain weight was the approach to higher rice yield.3.With the delayed sowing date,the dates of rice stem elongation,heading and maturity were postponed,and the entire rice growth duration were highly significantly shortened.While the rice growth duration in response to sowing date was different among rice types and different latitudes.The comparison of I and VI sowing date treatments showed that the reduced days of entire growth duration among different types of rice at Luoshan and Xincai sites were 12.0?17.0 d,and at Yuanyang site was 11.0?15.0 d.Thus if the sowing date was delayed by 5 d,the entire growth duration would be shortened by 2.4?3.4 and 2.2?3.0 d at different sites,respectively.The shortened range of entire growth duration among different rice types was early-maturing late japonica rice>late-maturing medium japonica conventional rice>late-maturing medium indica hybrid rice>medium-maturing medium japonica rice>late-maturing medium japonica hybrid rice.In the same sowing date,the entire growth duration of rice was prolonged with the rise of latitude.Moreover the prolonged days of entire growth duration among latitudes were more for rice types with longer growth duration than other rice types.The variation of entire rice growth duration among sowing dates was resulted from the variation of duration from sowing to stem elongation.The effective accumulative temperature and accumulate sunshine hours were more in early sowing date treatment and less in late sowing date treatment,indicating a higher temperature-light utilization of rice with earlier sowing date.In the same sowing date,the late-maturing rice had more effective accumulative temperature and accumulate sunshine hours than medium-maturing rice and late-maturing medium indica hybrid rice.4.The population and single plant dry matter accumulation showed significant response to sowing dates.With the delayed sowing date,the population and single plant dry matter accumulation at effective leaf age critical stage,stem elongation stage,heading stage and maturity stage were significantly reduced.In the same sowing date,the japonica hybrid rice had the largest population and single plant dry matter accumulation at the main stages among all test rice.In addition,the early-maturing late japonica rice was of larger population and single plant dry matter accumulation at the main stages than other rice,and such traits at heading and maturity stages showed significant difference among different types of rice.From sowing to stem elongation stage,the population dry matter accumulation was reduced with the delayed sowing date,and such traits of late-maturing medium japonica conventional rice were significantly larger than other rice.From stem elongation to heading stage,the population dry matter accumulation was increased firstly and then decreased with the delayed sowing date,and such traits of early-maturing late japonica rice were significantly larger than other rice.From heading to maturity stage,the population dry matter accumulation was decreased with the delayed sowing date,and such traits of late-maturing medium japonica hybrid rice were significantly larger than other rice.The trends of population dry matter accumulation among different types of rice in the Yunan site were different from those in Yuzhong and Yubei sites.In the Yunan site,the population dry matter accumulation from sowing to stem elongation stage of late-maturing medium japonica rice and early-maturing late japonica rice were significantly larger than other rice,from stem elongation to heading stage of early-maturing late japonica rice were significantly larger than other rice,and from heading to maturity stage showed insignificant difference among different types of rice.5.With the delayed sowing date,the medium-maturing medium japonica rice,late-maturing medium japonica rice improved the processing and appearance quality and deteriorated the nutrition,cooking and eating quality;the early-maturing late medium japonica rice had worse appearance and nutrition quality but better processing,cooking and eating quality;the later-maturing medium indica hybrid rice had decreased appearance quality but increased processing,nutrition,cooking and eating quality.In addition,the variations of rice quality of different types of rice in response to sowing dates were different.In addition,large differences of rice quality were observed among different types and latitudes.The rice processing and appearance quality were better in the high latitude areas than in the low latitude areas.In conclusion,with the delayed sowing date,the processing quality of medium-maturing medium japonica rice and late-maturing medium japonica rice was improved,but the nutrition quality became worse,while the processing quality of early-maturing late japonica rice became inferior,but nutrition quality became better.6.Analysis of“indica rice to japonica rice" showed that the average yield of japonica rice was significantly larger than indica rice in the same sowing date.Compared to indica rice,the japonica conventional rice increased the yield by 10.90 and 10.97 t/hm2 with increase rates of 13.49%and 15.23%in the two years,respectively;the japonica hybrid rice increased the yield by 11.42 and 11.40 t/hm2 with increase rates of 18.46%and 19.75%in the two years,respectively.In different sowing date,the yield of the japonica conventional rice and japonica hybrid rice were 13.25%?19.33%and 17.59%?25.69%larger than late-maturing medium indica hybrid rice.Relative larger total spikelets per hectare,higher filled grain grade and bigger 1000-grain weight were the approach for japonica rice produced more yield than indica rice.The processing,cooking and eating quality of most japonica rice were better than indica rice.In addition,the appearance and nutrition quality of medium-maturing medium japonica rice were worse than indica rice,but those of early-maturing late japonica rice were better than indica rice.The physical characteristics of "indica rice to japonica rice" were as follows:1.The growth duration duration of japonica rice were longer than indica rice and japonica rice was more adapted to cool weather at the late period of grain filling,increasing temperature-light utilization;2.Stronger photosynthetic capacity of japonica rice at the late growth period could synchronously increase dry matter weight and grain filling.3.The japonica rice improved the resistance to cold and premature senescence with strong stem and sheath to resist lodging,which guaranteed the enrichment and support of large sink.4.Compared to indica rice,japonica rice was more suitable for mechanized operation,used more temperature-light resources,and improved rice quality with high-stable yield.The results indicated that the comprehensive productivity of japonica rice was higher than indica rice.Thus this study recommended that late-maturing medium japonica hybrid rice and early-maturing late japonica rice were the best choice for rice production in Yunan and Yuzhong district with rice-wheat rotation system,while late-maturing medium japonica conventional rice and medium-maturing medium japonica rice were sub-suitable here.In the Yubei district with rice-wheat rotation system,the late-maturing medium japonica hybrid rice and late-maturing medium japonica conventional rice were better choice than medium-maturing medium japonica rice and early-maturing late japonica rice. |
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