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Abstract [Objectives] This study was conducted to further explore the yield increasing potential of Codonopsis pilosula， and to seek seedlings suitable for efficient production of C. pilosula.
[Methods] The effects of C. pilosula seedlings of different sizes on root yield and commercial quality under different cultivation densities were studied.
[Results] The fourthgrade seedlings had the least input， the highest yield of 6 948 kg/hm2， the largest outputtoinput ratio at 18.3， the highest root weight proportion of the secondgrade product at 58.1%， and the lowest root weight proportion of the firstgrade product at 17.6%. Considering the yield， quality and economic benefits comprehensively， the treatment of the fourthgrade seedlings （seedling diameter≤4 mm） is the best choice， and the suitable plant spacing is 8 cm×22 cm.
[Conclusions] The study provided a reference basis for the cost saving and efficiency improvement of C. pilosula production.
Key words Seedling; Codonopsis pilosula; Yield; Commercial quality; Effect
Codonopsis pilosula produced in Changzhi is Ludang， which comes from the name of the producing area （Changzhi was called Shangdang County in the Qin Dynasty， and changed to Luzhou in the Northern Zhou Dynasty）. Ludang is an authentic medicinal material in Shanxi. In terms of plant taxonomy， it belongs to Codonopsis in Campanulaceae， and is produced in Changzhi， Licheng， Pingshun， Lingchuan， Huguan， Wutai and other places in Shanxi. C. codonopsis is a commonly used tonic medicine， which has the effects of strengthening spleen and tonifying lung， and nourishing blood and promoting the secretion of saliva or body fluid[1].
Some Chinese scholars such as Ji et al.[2]， Cai et al.[3]and Huang et al.[4]have done research work on the cultivation， chemical composition， processing and other aspects of C. codonopsis. However， there have been few studies on the effects of seedling grades on the growth and yield of C. codonopsis. It is only cultivated and processed according to traditional experience in various producing areas， and it is difficult to control the yield of C. codonopsis. At present， the seedlings of varieties that had been studied include Astragalus membranaceus[5]， Gentiana macrophylla， Paris polyphylla， Paeonia suffruticosa Andr.， Ophiopogon japonicus （Linn. f.） KerGawl and C. codonopsis. Guan Qingxia from Gansu Province conducted a graded cultivation test on C. codonopsis seedlings in 2004， but the seedling diameter range was small， and comparison was not performed under different cultivation densities. In order to further explore the yield increasing potential of C. codonopsis， and to seek the seedling grade suitable for efficient production of C. codonopsis， the yield increasing potential of C. codonopsis seedlings of different grades was further verified under the same cultivation conditions. This study will provide a reference for cost saving and efficiency improvement of C. codonopsis production.
Materials and Methods
General situation of the research area
The research area is located in Pingshun County， Changzhi City， Shanxi Province. It has a warm temperate semihumid continental monsoon climate， with an altitude of 1 100 m， an average annual temperature of 9 ℃， and an annual precipitation of 900 mm. The frost period is from early November to mid April， and the frostfree period is 150 d. The soil is brownblack loam.
Experimental design
This experiment investigated such two factors as seedling grade and density. The seedlings were classified into five grades： A， B， C， D， and E. and the density H had five gradients： 8 cm×22 cm， 12 cm×30 cm， 10 cm×25 cm， and 7.5 cm×25 cm， 6 cm×20 cm. The seedlings were transplanted on April 15. A was the firstgrade seedlings， with a seedling diameter≥8 mm and an average root length of 20 cm; B was the secondgrade seedlings with a seedling diameter≥6 mm and an average root length of 18 cm; C was the thirdgrade seedlings with a seedling diameter of 4-6 mm and an average root length of 15 cm; D was the fourthgrade seedlings with a seedling diameter≤4 mm and an average root length of 14 cm; and E was the nongraded seedlings with a seedling diameter of 5 mm and an average root length of 15 cm.The plots had an area of 30 cm×6 cm each， and were randomly arranged without repetition.
Experimental methods
The cultivation management was the same as conventional management. The plants were collected uniformly on October 12， 2018. For each plot， the sampling area was 0.5 m2; the total weight of fresh roots was measured， and the number of plants was recorded; and 10 plants were randomly selected to measure root length and root thickness， followed by the calculation of the average values. After drying naturally， the total dry weight was measured， and the plant number of the samples in the plot was recorded; and after grading the samples according to different commodity grades， the root weight was measured and the plant number were recorded as well for each grade. The root length was measured with a ruler in accordance with the main root length. The root diameter was measured with a vernier caliper 1 cm away from the reed head. And the root weight was measured with an electronic scale. The drying rate was calculated according to following equation： Drying rate （%）=Dry weight of medicinal material/Fresh weight of medicinal material×100%. Statistical analysis of data
The statistical analysis softwares， WPS 2019 and SPSS19.0 were used to perform variance analysis and correlation analysis on the experimental data， and charting was performed in Excel.
Results and Analysis
Effects of seedling grades on the growth of C. codonopsis
The measurement results showed that the growth of the firstgrade seedlings was significantly weaker than that of the second and thirdgrade seedlings， and was weaker than the control as well. It can be seen in Table 1 that under the same cultivation density， as the diameter of C. codonopsis seedlings increased， the weight of single plant decreased. The weight of the roots of single firstgrade seedling decreased by 12.7% compared with that before planting， while that of single fourthgrade seedling increased by 91.8%. Under different planting densities， as the diameter of C. codonopsis seedlings increased， the singleplant weight decreased first and then increased， and the single plant weights of treatments B， C and D increased significantly compared with those before planting， with the weight gain rates of 33.3%， 77.1% and 89.4%， respectively， while the weight of single plant in treatment A decreased， with a weight gain rate of -10.0%.
Effects of seedling grades on the yield of C. codonopsis
Yield measurement results showed that under the same cultivation density， the yield increased first and then decreased with the seedling grade. And the yield of the fourthgrade seedling increased most， followed by the secondgrade seedlings taking second place， and the firstgrade seedlings yielded the lowest. Under different cultivation densities， the yield decreased with the increase of seedling diameter. The yield of treatment D was the highest at 7 860 kg， followed by that of treatment C， and the yield of treatment A was the lowest at 2 775 kg. Under different cultivation densities， the yield decreased with the increase of seedling diameter， showing the highest value of 7 860 kg in treatment D， followed by treatment C， and the lowest value of 2 775 kg in treatment A.
Investigation and analysis on production input and output of C. codonopsis under different seedling grade
Under the same cultivation density， with the diameter of C. codonopsis seedlings increasing， the seedling weight per unit area increased， the seedling input increased， the yield of medicinal materials decreased， the output of medicinal materials decreased， and the outputinput ratio decreased thereby. The firstgrade seedlings per hectare exhibited a largest seedling weight of 6 253.5kg， and the input per hectare of seedlings was 62 532 yuan， but the yield of medicinal materials was the lowest at 5 550 kg， which lead to the lowest output of 83 239.5 yuan， and the outputinput ratio was the smallest at 1.3. The seedling weight per unit area for the fourthgrade seedlings was the smallest at 568.5 kg， but its output of medicinal materials was the highest at 104 218.5 yuan， leading to the largest outputinput ratio of 18.3. Under different cultivation densities， the largest outputinput ratio was 14.1 in treatment D which had the largest dry weight of 19 080kg/hm2. The drying rate was the largest in treatment A2， followed by treatment B2. Commercial quality of C. codonopsis
The C. codonopsis seedlings of different sizes exhibited significantly higher root weight and plant number proportions for the secondgrade product than for the firstgrade and thirdgrade products. The root weight of the secondgrade product accounted for 58.1%， and the firstgrade product exhibited a minimum of 17.6%. The secondgrade product also showed the highest plant number proportion of 53.9%， and the firstgrade product had the lowest value at 9.2%.
With the increase of seedling size， the root weight proportion of the secondgrade product decreased first and then increased， while the root weight proportion of the thirdgrade product increased and then decreased. The fourthgrade seedlings showed the highest root weight proportion of the secondgrade product at 72%， while thirdgrade seedling exhibited the lowest values at 41%. As to the plant number proportion of the secondgrade product， the highest and lowest values were also observed for the fourthgrade seedlings （75%） and thirdgrade seedling （45.5%）， respectively.
Under the same cultivation density， the output value of C. codonopsis first increased and then decreased as the diameter of C. codonopsis seedlings increased. The output value of the secondgrade seedlings was the largest at 39 709.5 yuan， and that of the fourthgrade seedling was the smallest， which was related to the small cultivation density. Under different cultivation density conditions， with the diameter of C. codonopsis seedlings increasing， the output value first decreased and then increased. The firstgrade seedlings showed the largest output value at the density of 12 cm ×30 cm， which was 61 350 yuan， which increased by 24 369 yuan compared with the output value of the control， with an increasing rate of 65.9%. Secondly， the output value of the fourthgrade seedlings at the density of 6 cm×20 cm was 53 434.5 yuan， which increased by 16 453.5 yuan compared with the control， with an increasing rate of 26.9%.
Conclusions and Discussion
Yang et al.[6]showed that C. codonopsi seedlings were divided into four grades： the first grade with a fresh weight of single seedling of 2.9-7.8 g， a seedling length of 23.2-36.0 cm and a seedling diameter of 0.46-0.71 mm， the second grade with a fresh weight of single seedling of 1.5-2.8 g， a seedling length of 22.6-26.3 cm and a seedling diameter of 0.35-0.50 mm， the third grade with a fresh weight of single seedling of 0.9-1.4 g， a seedling length of 18.6-22.5 cm and a seedling diameter of 0.28-0.35mm， and the fourth grade with a fresh weight of single seedling of 0.2-0.8 g， a seedling length of 6.0-18.0 cm and a seedling diameter of 0.18-0.27 mm. It is suggested that in production practice， good quality and highgrade seedlings should be selected， and first and secondgrade seedlings should be used in standardized cultivation. This is consistent with the results of this study， and the diameter of the secondgrade seedlings is consistent with the diameter of the fourthgrade seedlings in this study. Wang et al.[7]showed that the firstgrade seedlings of C. codonopsi had the fastest emergence and the highest yield， which were significantly higher than the second and thirdgrade seedlings （P<0.05）; and the smaller the seedlings， the faster the growth rate. This study concluded that the weight gain rate of the thirdgrade seedlings was large， while that of the firstgrade seedlings decreased instead. The yield of the fourthgrade seedlings was the highest， which is conform to the diameter of the firstgrade seedlings in the study of Wang et al.[7]. Some scholars have graded seedlings of medicinal plants such as Glycyrrhiza uralensis Fisch[8]， P. polyphylla[9]， Dendrobium nobile Lindl[10]， Aquilaria sinensis[11]and C. codonopsi[12]. The seedling length and seedling thickness were used as grading indicators to grade C. codonopsi seedlings in this study， and the yield of medicinal materials and the commercial output value were compared. From the point of view of commercial output value， the firstgrade seedlings for planting achieved the largest commercial output value of 61 350 yuan， followed by the fourthgrade seedling treatment （53 434.5 yuan）. Choosing the firstgrade seedlings for planting can achieve higher economic benefits， and the suitable row spacing for cultivation is 12 cm×30 cm. From the perspective of the outputinput ratio of medicinal materials， under the conditions of equal density and high density cultivation， the outputinput ratio of the fourthgrade seedlings was the largest， accompanied with the largest weight gain rate， and the suitable row spacing for cultivation is 8 cm×22 cm. Considering the yield， quality and economicbenefits comprehensively， the fourthgrade seedling treatment is the best choice， and the suitable plant spacing is 8 cm × 22 cm. Determining the level and planting density of C. codonopsi while saving costs and increasing production to maximize the economic output value of C. codonopsi industry is of great significance for the development of C. codonopsi industry and the utilization of environmental resources.
References
[1] Chinese Pharmacopoeia Commission. Chinese Pharmacopoeia[M]. Beijing： China Medical Science and Technology Press， 2015： 281-282. （in Chinese）
[2] JI Y， QI J， CAI W， et al. Effects of different densities and cultivation methods on Codonopsis pilosula seed yield and its composition[J]. Journal of Chinese Medicinal Materials，2015，38（12），2473-2475. （in Chinese）
[3] CAI ZP， WANG HX， WANG GX， et al. Effects of different seedling raising models on the quality of Codonopsis pilosula seedlings in Weiyuan， Gansu[J]. Journal of Chinese Medicinal Materials 2017， 40（04）： 779-781. （in Chinese）
[4] HUANG YY， ZHANG Y， KANG LP， et al. Research progress on chemical constituents and their pharmacological activities of plant from Codonopsis[J]. Chinese Traditional and Herbal Drugs， 2018， （1）： 1169-1170. （in Chinese）
[5] GUAN QX， LI CD. Effect of Astragalus membranaceus seedlings at different levels[J]. Agricultural ScienceTechnology and Information 2015， （15）： 65-66. （in Chinese） [6] YANG FD， LUO WR， CUI ZJ， et al. Codonopsis pilosula seedlings grading standards[J]. Lishizhen Medicine and Materia Medica Research2017， 28（02）： 452-454. （in Chinese）
[7] WANG HZ， LIAN ZX， LU GD， et al. The relationship between the grade of Codonopsis pilosula seedlings and the yield and quality of medicinal materials[J]. China Journal of Chinese Materia Medica 2016， 41（21）： 3950-3955. （in Chinese）
[8] HOU J， YAN LB， ZHAO GL， et al. The relationship between Glycyrrhiza uralensis seedling grade and plant biological chain accumulation， medicinal material yield and quality[J]. Journal of Chinese Medicinal Materials， 2015， 38（2）： 221. （in Chinese）
[9] CHEN C， KANG PD， TANG WW， et al. Growth of different grades of Paris polyphylla var. yunnanensis （Franch.） Hand.Mass[J]. Journal of Yunnan University of Traditional Chinese Medicine， 2009， 32（5）： 52. （in Chinese）
[10] PAN CM， HUANG CC， ZHENG FH， et al. Study on grading standard of Aquilaria sinensis seedlings[J]. Journal of Guangzhou University of Traditional Chinese Medicine，2012，29（ 2） ： 180. （in Chinese）
[11] TANG L， ZHANG LX， WANG YQ， et al. Research of seedling quality grading of Dendrobium nobile[J]. Journal of Chinese Medicinal Materials， 2012， 35（1）： 12. （in Chinese）
[12] LI RJ， CHEN Y， GUO FX， et al. Study on the quality grading standards of Codonopsis pilosula var. modesta （Nannf.） L. T. Shen[J]. China Journal of Chinese Materia Medica， 2012， 37（20）： 3041. （in Chinese）
[Methods] The effects of C. pilosula seedlings of different sizes on root yield and commercial quality under different cultivation densities were studied.
[Results] The fourthgrade seedlings had the least input， the highest yield of 6 948 kg/hm2， the largest outputtoinput ratio at 18.3， the highest root weight proportion of the secondgrade product at 58.1%， and the lowest root weight proportion of the firstgrade product at 17.6%. Considering the yield， quality and economic benefits comprehensively， the treatment of the fourthgrade seedlings （seedling diameter≤4 mm） is the best choice， and the suitable plant spacing is 8 cm×22 cm.
[Conclusions] The study provided a reference basis for the cost saving and efficiency improvement of C. pilosula production.
Key words Seedling; Codonopsis pilosula; Yield; Commercial quality; Effect
Codonopsis pilosula produced in Changzhi is Ludang， which comes from the name of the producing area （Changzhi was called Shangdang County in the Qin Dynasty， and changed to Luzhou in the Northern Zhou Dynasty）. Ludang is an authentic medicinal material in Shanxi. In terms of plant taxonomy， it belongs to Codonopsis in Campanulaceae， and is produced in Changzhi， Licheng， Pingshun， Lingchuan， Huguan， Wutai and other places in Shanxi. C. codonopsis is a commonly used tonic medicine， which has the effects of strengthening spleen and tonifying lung， and nourishing blood and promoting the secretion of saliva or body fluid[1].
Some Chinese scholars such as Ji et al.[2]， Cai et al.[3]and Huang et al.[4]have done research work on the cultivation， chemical composition， processing and other aspects of C. codonopsis. However， there have been few studies on the effects of seedling grades on the growth and yield of C. codonopsis. It is only cultivated and processed according to traditional experience in various producing areas， and it is difficult to control the yield of C. codonopsis. At present， the seedlings of varieties that had been studied include Astragalus membranaceus[5]， Gentiana macrophylla， Paris polyphylla， Paeonia suffruticosa Andr.， Ophiopogon japonicus （Linn. f.） KerGawl and C. codonopsis. Guan Qingxia from Gansu Province conducted a graded cultivation test on C. codonopsis seedlings in 2004， but the seedling diameter range was small， and comparison was not performed under different cultivation densities. In order to further explore the yield increasing potential of C. codonopsis， and to seek the seedling grade suitable for efficient production of C. codonopsis， the yield increasing potential of C. codonopsis seedlings of different grades was further verified under the same cultivation conditions. This study will provide a reference for cost saving and efficiency improvement of C. codonopsis production.
Materials and Methods
General situation of the research area
The research area is located in Pingshun County， Changzhi City， Shanxi Province. It has a warm temperate semihumid continental monsoon climate， with an altitude of 1 100 m， an average annual temperature of 9 ℃， and an annual precipitation of 900 mm. The frost period is from early November to mid April， and the frostfree period is 150 d. The soil is brownblack loam.
Experimental design
This experiment investigated such two factors as seedling grade and density. The seedlings were classified into five grades： A， B， C， D， and E. and the density H had five gradients： 8 cm×22 cm， 12 cm×30 cm， 10 cm×25 cm， and 7.5 cm×25 cm， 6 cm×20 cm. The seedlings were transplanted on April 15. A was the firstgrade seedlings， with a seedling diameter≥8 mm and an average root length of 20 cm; B was the secondgrade seedlings with a seedling diameter≥6 mm and an average root length of 18 cm; C was the thirdgrade seedlings with a seedling diameter of 4-6 mm and an average root length of 15 cm; D was the fourthgrade seedlings with a seedling diameter≤4 mm and an average root length of 14 cm; and E was the nongraded seedlings with a seedling diameter of 5 mm and an average root length of 15 cm.The plots had an area of 30 cm×6 cm each， and were randomly arranged without repetition.
Experimental methods
The cultivation management was the same as conventional management. The plants were collected uniformly on October 12， 2018. For each plot， the sampling area was 0.5 m2; the total weight of fresh roots was measured， and the number of plants was recorded; and 10 plants were randomly selected to measure root length and root thickness， followed by the calculation of the average values. After drying naturally， the total dry weight was measured， and the plant number of the samples in the plot was recorded; and after grading the samples according to different commodity grades， the root weight was measured and the plant number were recorded as well for each grade. The root length was measured with a ruler in accordance with the main root length. The root diameter was measured with a vernier caliper 1 cm away from the reed head. And the root weight was measured with an electronic scale. The drying rate was calculated according to following equation： Drying rate （%）=Dry weight of medicinal material/Fresh weight of medicinal material×100%. Statistical analysis of data
The statistical analysis softwares， WPS 2019 and SPSS19.0 were used to perform variance analysis and correlation analysis on the experimental data， and charting was performed in Excel.
Results and Analysis
Effects of seedling grades on the growth of C. codonopsis
The measurement results showed that the growth of the firstgrade seedlings was significantly weaker than that of the second and thirdgrade seedlings， and was weaker than the control as well. It can be seen in Table 1 that under the same cultivation density， as the diameter of C. codonopsis seedlings increased， the weight of single plant decreased. The weight of the roots of single firstgrade seedling decreased by 12.7% compared with that before planting， while that of single fourthgrade seedling increased by 91.8%. Under different planting densities， as the diameter of C. codonopsis seedlings increased， the singleplant weight decreased first and then increased， and the single plant weights of treatments B， C and D increased significantly compared with those before planting， with the weight gain rates of 33.3%， 77.1% and 89.4%， respectively， while the weight of single plant in treatment A decreased， with a weight gain rate of -10.0%.
Effects of seedling grades on the yield of C. codonopsis
Yield measurement results showed that under the same cultivation density， the yield increased first and then decreased with the seedling grade. And the yield of the fourthgrade seedling increased most， followed by the secondgrade seedlings taking second place， and the firstgrade seedlings yielded the lowest. Under different cultivation densities， the yield decreased with the increase of seedling diameter. The yield of treatment D was the highest at 7 860 kg， followed by that of treatment C， and the yield of treatment A was the lowest at 2 775 kg. Under different cultivation densities， the yield decreased with the increase of seedling diameter， showing the highest value of 7 860 kg in treatment D， followed by treatment C， and the lowest value of 2 775 kg in treatment A.
Investigation and analysis on production input and output of C. codonopsis under different seedling grade
Under the same cultivation density， with the diameter of C. codonopsis seedlings increasing， the seedling weight per unit area increased， the seedling input increased， the yield of medicinal materials decreased， the output of medicinal materials decreased， and the outputinput ratio decreased thereby. The firstgrade seedlings per hectare exhibited a largest seedling weight of 6 253.5kg， and the input per hectare of seedlings was 62 532 yuan， but the yield of medicinal materials was the lowest at 5 550 kg， which lead to the lowest output of 83 239.5 yuan， and the outputinput ratio was the smallest at 1.3. The seedling weight per unit area for the fourthgrade seedlings was the smallest at 568.5 kg， but its output of medicinal materials was the highest at 104 218.5 yuan， leading to the largest outputinput ratio of 18.3. Under different cultivation densities， the largest outputinput ratio was 14.1 in treatment D which had the largest dry weight of 19 080kg/hm2. The drying rate was the largest in treatment A2， followed by treatment B2. Commercial quality of C. codonopsis
The C. codonopsis seedlings of different sizes exhibited significantly higher root weight and plant number proportions for the secondgrade product than for the firstgrade and thirdgrade products. The root weight of the secondgrade product accounted for 58.1%， and the firstgrade product exhibited a minimum of 17.6%. The secondgrade product also showed the highest plant number proportion of 53.9%， and the firstgrade product had the lowest value at 9.2%.
With the increase of seedling size， the root weight proportion of the secondgrade product decreased first and then increased， while the root weight proportion of the thirdgrade product increased and then decreased. The fourthgrade seedlings showed the highest root weight proportion of the secondgrade product at 72%， while thirdgrade seedling exhibited the lowest values at 41%. As to the plant number proportion of the secondgrade product， the highest and lowest values were also observed for the fourthgrade seedlings （75%） and thirdgrade seedling （45.5%）， respectively.
Under the same cultivation density， the output value of C. codonopsis first increased and then decreased as the diameter of C. codonopsis seedlings increased. The output value of the secondgrade seedlings was the largest at 39 709.5 yuan， and that of the fourthgrade seedling was the smallest， which was related to the small cultivation density. Under different cultivation density conditions， with the diameter of C. codonopsis seedlings increasing， the output value first decreased and then increased. The firstgrade seedlings showed the largest output value at the density of 12 cm ×30 cm， which was 61 350 yuan， which increased by 24 369 yuan compared with the output value of the control， with an increasing rate of 65.9%. Secondly， the output value of the fourthgrade seedlings at the density of 6 cm×20 cm was 53 434.5 yuan， which increased by 16 453.5 yuan compared with the control， with an increasing rate of 26.9%.
Conclusions and Discussion
Yang et al.[6]showed that C. codonopsi seedlings were divided into four grades： the first grade with a fresh weight of single seedling of 2.9-7.8 g， a seedling length of 23.2-36.0 cm and a seedling diameter of 0.46-0.71 mm， the second grade with a fresh weight of single seedling of 1.5-2.8 g， a seedling length of 22.6-26.3 cm and a seedling diameter of 0.35-0.50 mm， the third grade with a fresh weight of single seedling of 0.9-1.4 g， a seedling length of 18.6-22.5 cm and a seedling diameter of 0.28-0.35mm， and the fourth grade with a fresh weight of single seedling of 0.2-0.8 g， a seedling length of 6.0-18.0 cm and a seedling diameter of 0.18-0.27 mm. It is suggested that in production practice， good quality and highgrade seedlings should be selected， and first and secondgrade seedlings should be used in standardized cultivation. This is consistent with the results of this study， and the diameter of the secondgrade seedlings is consistent with the diameter of the fourthgrade seedlings in this study. Wang et al.[7]showed that the firstgrade seedlings of C. codonopsi had the fastest emergence and the highest yield， which were significantly higher than the second and thirdgrade seedlings （P<0.05）; and the smaller the seedlings， the faster the growth rate. This study concluded that the weight gain rate of the thirdgrade seedlings was large， while that of the firstgrade seedlings decreased instead. The yield of the fourthgrade seedlings was the highest， which is conform to the diameter of the firstgrade seedlings in the study of Wang et al.[7]. Some scholars have graded seedlings of medicinal plants such as Glycyrrhiza uralensis Fisch[8]， P. polyphylla[9]， Dendrobium nobile Lindl[10]， Aquilaria sinensis[11]and C. codonopsi[12]. The seedling length and seedling thickness were used as grading indicators to grade C. codonopsi seedlings in this study， and the yield of medicinal materials and the commercial output value were compared. From the point of view of commercial output value， the firstgrade seedlings for planting achieved the largest commercial output value of 61 350 yuan， followed by the fourthgrade seedling treatment （53 434.5 yuan）. Choosing the firstgrade seedlings for planting can achieve higher economic benefits， and the suitable row spacing for cultivation is 12 cm×30 cm. From the perspective of the outputinput ratio of medicinal materials， under the conditions of equal density and high density cultivation， the outputinput ratio of the fourthgrade seedlings was the largest， accompanied with the largest weight gain rate， and the suitable row spacing for cultivation is 8 cm×22 cm. Considering the yield， quality and economicbenefits comprehensively， the fourthgrade seedling treatment is the best choice， and the suitable plant spacing is 8 cm × 22 cm. Determining the level and planting density of C. codonopsi while saving costs and increasing production to maximize the economic output value of C. codonopsi industry is of great significance for the development of C. codonopsi industry and the utilization of environmental resources.
References
[1] Chinese Pharmacopoeia Commission. Chinese Pharmacopoeia[M]. Beijing： China Medical Science and Technology Press， 2015： 281-282. （in Chinese）
[2] JI Y， QI J， CAI W， et al. Effects of different densities and cultivation methods on Codonopsis pilosula seed yield and its composition[J]. Journal of Chinese Medicinal Materials，2015，38（12），2473-2475. （in Chinese）
[3] CAI ZP， WANG HX， WANG GX， et al. Effects of different seedling raising models on the quality of Codonopsis pilosula seedlings in Weiyuan， Gansu[J]. Journal of Chinese Medicinal Materials 2017， 40（04）： 779-781. （in Chinese）
[4] HUANG YY， ZHANG Y， KANG LP， et al. Research progress on chemical constituents and their pharmacological activities of plant from Codonopsis[J]. Chinese Traditional and Herbal Drugs， 2018， （1）： 1169-1170. （in Chinese）
[5] GUAN QX， LI CD. Effect of Astragalus membranaceus seedlings at different levels[J]. Agricultural ScienceTechnology and Information 2015， （15）： 65-66. （in Chinese） [6] YANG FD， LUO WR， CUI ZJ， et al. Codonopsis pilosula seedlings grading standards[J]. Lishizhen Medicine and Materia Medica Research2017， 28（02）： 452-454. （in Chinese）
[7] WANG HZ， LIAN ZX， LU GD， et al. The relationship between the grade of Codonopsis pilosula seedlings and the yield and quality of medicinal materials[J]. China Journal of Chinese Materia Medica 2016， 41（21）： 3950-3955. （in Chinese）
[8] HOU J， YAN LB， ZHAO GL， et al. The relationship between Glycyrrhiza uralensis seedling grade and plant biological chain accumulation， medicinal material yield and quality[J]. Journal of Chinese Medicinal Materials， 2015， 38（2）： 221. （in Chinese）
[9] CHEN C， KANG PD， TANG WW， et al. Growth of different grades of Paris polyphylla var. yunnanensis （Franch.） Hand.Mass[J]. Journal of Yunnan University of Traditional Chinese Medicine， 2009， 32（5）： 52. （in Chinese）
[10] PAN CM， HUANG CC， ZHENG FH， et al. Study on grading standard of Aquilaria sinensis seedlings[J]. Journal of Guangzhou University of Traditional Chinese Medicine，2012，29（ 2） ： 180. （in Chinese）
[11] TANG L， ZHANG LX， WANG YQ， et al. Research of seedling quality grading of Dendrobium nobile[J]. Journal of Chinese Medicinal Materials， 2012， 35（1）： 12. （in Chinese）
[12] LI RJ， CHEN Y， GUO FX， et al. Study on the quality grading standards of Codonopsis pilosula var. modesta （Nannf.） L. T. Shen[J]. China Journal of Chinese Materia Medica， 2012， 37（20）： 3041. （in Chinese）