| The experiment was carried out in the experimental field of Agricultural College of Yangzhou University from 2019 to 2020.The soil was sandy loam with medium to upper soil fertility.The soil pH was 6.0,total nitrogen was 1.2gkg-1,alkali hydrolyzable nitrogen was 95.6mg kg-1,available potassium was 88.3mg kg-1,and available phosphorus was 35.2mg kg-1.Aiming at the cultivation of strong seedlings of machine transplanted rice under the condition of rice wheat double cropping,the effects of strong seedling agent and seeding rate on the quality and yield of long seedling age seedlings were carried out.The first experiment set up the same sowing date,sowing rate(May 14)and seedling strengthening agent to cultivate long seedling age seedlings×28 cm,dry seed)2 levels;There were four levels of seedling strengthening agent:doxazole,mixian metalaxyl,miaozhuangfeng and CK.The second experiment was the three factors experiment of different sowing date transplanting on the same day,including sowing amount,seedling strengthening agent and seedling age.The main area was different seedling age,and the secondary area was sowing amount and seedling strengthening agent.The seedling age was set at three levels of 20d,25d and 30 d;The sowing rate was 90 g/plate and 120 g/plate;The seedling strengthening agent was divided into four levels:A:doxazole,B:mixam·metalaxyl,C:Miao Zhuangfeng and no application of seedling strengthening agent(control).Seeds were sown after seed dressing on May 15,May 20 and May 25.Field transplanting was carried out on June 14,and artificial mechanical transplanting was used.The distance between plants and rows is 30cm×12 cm,4 seedlings per hole.The main test results are as follows.1.Under the condition of this study,seedling strengthening agent and sowing amount can enhance the quality of seedlings and prolong the suitable planting period.The results showed that the seedling quality of the treatments of doxocarbazole,mixian,metalaxyl and Miao Zhuangfeng was higher than that of CK.Under the condition of 25 d and 30 d long seedling age,the seedling height could be dwarfed by 0.3cm～3cm and 0.3cm～3.4cm,and the leaf area,stem base width and SPAD value of expanded leaf increased by 23.7%～20.1%～33.3%,5.3%～10.5%and 7.5%～16.3%,respectively.Among them,Miao Zhuangfeng seedling strengthening agent had the best seedling quality at the age of 25 d and 30 d,with dark green leaves and thick stem base,which was 0.3 mm thicker than the control.It had the best effect on extending the suitable planting period and increasing the elasticity of seedling age.Compared with 120g/plate sowing rate,90g/plate sowing rate could significantly improve the seedling quality at long seedling age stage,shorten the seedling height by 1.5cm and thicken the stem base by 0.2mm.In the stage of long seedling age,the seeding rate of Miao Zhuangfeng at 90g/plate was good,and the seedling quality was at a high level with high plumpness.However,at the sowing rate of 120g/plate,although the seedling quality was better,the plumpness was not as good as that of mixam and metalaxyl.In the cultivation of long seedling age seedlings,Miao Zhuang Feng treatment has obvious advantages.In the area of rice wheat double cropping system,using seedling strengthening agent and reducing sowing rate can cultivate strong seedlings with long seedling age,so as to alleviate the shortage of rice wheat stubble.The application of seedling strengthening agent +90g/plate sowing rate is recommended,and the seedling quality of this treatment is at the best level at the stage of long seedling age.2.The results showed that the rice yield of all seedling strengthening agents was higher than that of CK.The highest yield of 90g/plate+a(doxorubicin)was obtained at 20 days of seedling age.The yield of B(mixian·metalaxyl)and C(miaozhuangfeng)was higher than that of a(doxorubicin·doxorubicin)and CK at 25 and 30 days of seedling age.The reason for high yield was that B and C seedling strengthening agents effectively improved the quality of seedlings.After the improvement of seedling quality,the number of spikelets increased by 2.7%～4.6%,while keeping the 1000 grain weight equal or slightly increased.Among them,C treatment could significantly improve the seed setting rate,increased by 1.43%.The main reason of high yield can be obtained by seedling strengthening agent and seeding rate is that it can effectively improve seedling quality in early stage,turn green and live trees quickly when transplanting,accumulate a large amount of material,reduce the occurrence of ineffective tillers and improve the ear rate.The yield of rice decreased with the extension of seedling age.After the improvement of seedling quality,the yield of B and C treatments could reach the level of 20d+120g/plate CK.In this experiment,with the extension of seedling age,the effective panicle,seed setting rate and 1000 grain weight decreased by 1.31～3.77,respectively(×104 hm-2),0.18%～0.56%,0.13～0.24g。The possible reason is that long seedling age shortened the field growth period,grain filling period and dry matter accumulation,which eventually led to yield reduction.In terms of sowing rate,the average yield of 90g/plate was 0.56t hm-2 higher than that of 120g/plate.Therefore,it is suggested that 90g/PAN+B or 90g/PAN+C can weaken the yield decline caused by low seedling quality,increase the elasticity of seedling age,prolong the suitable planting period,and alleviate the contradiction of stubble.3.This experiment shows that enhancing seedling quality can improve rice quality.Compared with CK,all seedling strengthening agents could increase brown rice rate,milled rice rate and head rice rate by 0.47%～0.98%,0.43%～0.70%and 1.45%～3.44%,respectively,which improved rice quality;The chalkiness area,chalkiness rate and chalkiness degree were significantly reduced by 3.57%～17.85%,1.05%～2.27%,1.13%～6.86%on average,and the appearance quality was increased;Compared with CK,the protein content,amylose content and gel consistency increased by 0.42%～1.17%,0.44%～1.17%and 0.62%～1.51%respectively.With the increase of seedling age and seeding rate,the processing quality,appearance quality and nutritional quality of rice decreased.The rice quality of Miao Zhuang Feng was better in the treatment of Seedling strengthening agent... |
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