Effect of stage fertilization on growth and development of tobacco seedlings in floating cultivation
[Objective]Scientific fertilization is one of the key technologies to determine the strength of tobacco seedlings.In view of the lack of precise management of nutrients in various stages of tobacco seedlings in floating cultivation,this study aims to clarify the appropriate nutrient concentration requirements for different growth stages of tobacco seedlings in floating cultivation,which has important theoretical and practical value for precise nutrient management in cultivating strong tobacco seedlings.[Method]Yunyan 87 was used as the experimental material,and the period from sowing to seedling transplantation(five-leaves stage)was categorized into three stages according to the fertilizer application nodes of seedling production:the stage I from sowing to the big cross(0-31 days after sowing);the stage II from the big cross to the four-leaf(32-38 days after sowing);and the stage III from the four-leaf to the five-leaf(39-42 days after sowing).The initial concentration of the nutrient solution was set up in sections.The concentrations of Stage I included 0(CK0),25,50,75,100(CK1),125,150,175,and 200 mg/L;The concentrations of Stage II and III were 150,160,170,180,190,and 200 mg/L,which were based on the appropriate concentration of the previous stage as the initial concentration.Agronomic traits and key physiological indicators of tobacco seedlings at three developmental stages were comprehensively assessed by multi-objective decision-making method.[Result]The growth of tobacco seedlings treated with 150 mg/L at stage I was vigorous.Compared with the CK0 and CK1 treatments,the plant height,stem diameter,maximum leaf length,maximum leaf width,number of primary lateral roots,and dry matter accumulation of tobacco seedlings were increased with various degrees.The increases in total root length,total root volume,total root surface area,and mean root diameter of tobacco seedlings ranged from 20.63%to 69.30%.Specifically,the activity of nitrate reductase and the content of chlorophyll were significantly increased.At stage II,tobacco seedlings treated with 150 mg/L exhibited stronger growth than those treated with 170 mg/L.Although plant height,stem diameter,maximum leaf length,and maximum leaf width were reduced,lateral root number increased by 4.28%and 0.39%,and underground fresh weight and underground dry weight increased by 25.00%and 17.40%respectively.Additionally,total root length and total root surface area increased significantly by 11.46%and 13.54%respectively.Furthermore,the levels of soluble protein content,chlorophyll content,and root vitality exhibited varying degrees of increase in comparison to the other treatments.At stage III,the tobacco seedlings treated with 160 mg/L exhibited vigorous growth.The stem diameter,maximum leaf length,maximum leaf width,root length,and lateral root number increased significantly compared with those treated with 150 mg/L.Additionally,the dry matter accumulation was significantly higher.The total root length,total root surface area,and total root volume showed significant increases of 20.33%,42.79%,and 26.05%respectively.This study found that the total amount of chlorophyll increased by 8.97%,root vigor improved by 10.98%,and nitrate reductase activity increased by 6.41%.[Conclusion]The optimal initial concentration of the nutrient solution for the three stages was 150,150,160 mg/L.
tobaccofloating seedlingsnutrient solution concentrationstage fertilizationseedling cultivationmulti-objective decision making
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