Research Article

Korean Journal of Plant Resources. 31 December 2018. 660-666
https://doi.org/10.7732/kjpr.2018.31.6.660

ABSTRACT


MAIN

  • Introduction

  • Materials and Methods

  •   Soil sampling and processing

  •   Soil pH and E.C (Electronic Conductivity)

  •   Available P2O5 and O.M (Organic Matter)

  •   Determination of T-N (Total Nitrogen)

  •   Exchangeable cations (K, Ca, Mg, Na)

  •   Statistical analysis

  • Results

  •   Soil chemistry by cultivation years

  •   Soil chemistry by transplanting of P. grandiflorum

  •   Soil chemistry by occurrence of root rot disease of P. grandiflorum

  • Discussion

Introduction

Platycodon grandiflorum, a perennial plant belonging to Campanulaceae, is native to all parts of Korea and is a wild vegetable which represents the only genus and species in the world (Park and Chae, 1996; Lee et al; 1999; Jeon et al., 2013). Moreover P. grandiflorum contains proteins, lipids, sugars, ash, iron, saponin, inulin and phytosterin. It is a very useful crop for medicinal purposes because it is known to exhibit various pharmacological actions such as expectorant, antitussive, antibacterial, hypotensive and hypoglycemic (Cho, 1984; Lee et al., 2010; Lee et al., 2014).

In recent years, the production of P. grandiflorum has increased from 6,112 tons in 2012 to 6,665 tons in 2016 (Forest Service, 2016). In order to produce P. grandiflorum with excellent pharmacological properties, long term cultivation is used for medicinal purposes but generally, it is known that transplanting and managing the crops for 3 years is being done to prevent root rot disease which occurs in long term cultivation (Lee et al., 1999; Kim and Cho, 2011).

For farmers who cultivate P. grandiflorum for medicinal purposes, long term cultivation through transplanting is continuously being carried out but it is difficult to select the land with the same conditions with land as used before transplanting. When fertilization and management of the cultivated land is carried out through farmer's practice, the yield and quality tend to be uneven and the important active ingredient content in the P. grandiflorum is affected (Jung et al., 1996; Lee et al., 2010). In addition, while the damage of root rot disease is great at a certain time when cultivation for 3 years, research on specific occurrence causes of the disease is still incomplete.

The purpose of this study is utilize the basic data for the reduction of the root rot disease and determine the soil environmental conditions for the long term cultivation of P. grandiflorum which is highly utilize as a medicinal resource through the investigation of chemical properties of the cultivated field compare and analyze the changes in various years.

Materials and Methods

Soil sampling and processing

In order to analyze the soil chemical properties where P. grandiflorum is cultivated by long term, one farm which does this practice for medicinal purposes, was selected and a total of 12 soil samples were collected from 3 fields, located in Okcheon gun, Chungbuk province in August 2017. Soil samples were collected from the soil of about 3 ㎝ from the root surface except for the topsoil layer (20 ㎝) (Fig. 2A). The collected soil samples were mixed with air-dried in the shade for two weeks and used as a soil chemical analysis sample using test sieve (No.10, 2 ㎜).

Soil pH and E.C (Electronic Conductivity)

Soil analysis was carried out three times on the basis of the Rural Development Administration soil chemical analysis (NIAST, 2000). Soil pH (soil acidity) and E.C were measured in 1:5 soil to water suspensions by electrode method (Orion 3 star, Thermo) (Fig. 2C).

Available P2O5 and O.M (Organic Matter)

Available P2O5 analysis was performed using the Lancaster method (UV2550PC, Pekinelmer) and Tyurin method were used for the analysis of available P2O5 and O.M (organic matter).

Determination of T-N (Total Nitrogen)

The Kjeldahl method (Bremner, 1965) was performed for total nitrogen (T-N) analysis by nitrogen auto analyser (K-350, Buchi distillation unit) (Fig. 2B). Soil was digested and distilled, NH4+ collected in the 2% boric acid solution was quantitatively titrated with acid.

Exchangeable cations (K, Ca, Mg, Na)

Exchangeable cations (K, Ca, Mg, Na) were analyzed using ICP (ICPE-9000, Shimadzu) after extraction using 1N-NH4OAc solution.

Statistical analysis

Statistical analysis was performed using Duncan's Multiple Range Test (DMRT) at 5% significance level for each comparison item using SAS (9.1 ver., SAS Institute Inc.) program.

Results

Soil chemistry by cultivation years

The soil chemistry was investigated in order to analyze the characteristics of the soil environment according to the long term cultivation of P. grandiflorum in the area of Samnam myeon, Okcheon gun, Chungbuk province in August 2017 (Fig. 1). The first site where the soil samples were collected, was cultivated it for 5 years (Samnam ri, Okcheon gun, Chungbuk province, 36° 17'51.2 "N, 127° 44'54.1" E), the second site was cultivated for 2 and 5 years (Gungchon ri, Okcheon gun, Chungbuk province, 36° 18'22.5 "N, 127° 45'23.9 "E) and third site was cultivated for 6, 11 and 15 years (Soseo ri, Okcheon gun, Chungbuk province, 36° 18'49.6" N 127° 46'10.2 "E) (Table 1).

http://static.apub.kr/journalsite/sites/kjpr/2018-031-06/N0820310609/images/kjpr_31_06_09_F1.jpg
Fig. 1.

Soil sampling cites for soil properties analysis at P. grandiflorum from 3 fields of Okcheon-gun, Chungbuk province. (A) Soil samples of cultivated for 5 years (non transplanted) collected from Samnam, Okcheon-gun. (B) Soil samples of cultivated for 2 years (non transplanted) and 5 years (transplanted) collected from Gwongchon, Okcheon-gun. (C) Soil samples of cultivated for 6 years (transplanted), 11 years (transplanted) and 15 years (transplanted) collected from Soseo, Okcheon-gun.

http://static.apub.kr/journalsite/sites/kjpr/2018-031-06/N0820310609/images/kjpr_31_06_09_F2.jpg
Fig. 2.

(A) 12 soil samples were collected from the root surface except for the topsoil layer (20 ㎝). Soil analysis was carried out on the basis of the Rural Development Administration soil chemical analysis. (B) Determination of T-N (Total Nitrogen) was performed by nitrogen auto analyzer (K-350, Buchi distillation unit). (C) Soil pH and E.C (Electronic Conductivity) were performed by electrode method (Orion 3 star, Thermo).

Table 1. List of soil samples collected from Okcheon-gun, Chungbuk province

Region No. Sample Number of
cultivated year
Trans-planting Variety
Samnam, Okcheon 1 5Y-NT-HZ 2 × Etteum
5Y-NT-DY
Gwongchon, Okcheon 2 2Y-NT-H 5 ×
2Y-NT-D
3 5Y-T-HX 5
5Y-T-D
Soseo, Okcheon 4 6Y-T-H 6
6Y-T-D
5 11Y-T-H 11
11Y-T-D
6 15Y-T-H 15
15Y-T-D
Z-Y: Cultivation year, NT: Non transplanted field, H: Healthy plant.
YD: Diseased plant.
XT: Transplanted field.

The results of soil environment survey according to year number of cultivations years were shown in Table 2. Generally, the pH was 4 to 6, indicating an acid to slightly acidic distribution. 2Y-NT-H was the lowest at 4.61 and 5Y-T-H was the highest at 6.35. In the case of E.C and T-N, the pH was similar but there was no significant difference according to the number of cultivation years. O.M content was the highest at 25.04 g/㎏ in the 5Y-T-H and it was similar to 25 g/㎏ on average O.M content at cultivated area of P. grandiflorum in Korea. But other soil samples were lower than average O.M content (Jung et al., 1996). The average available P2O5 content in the P. grandiflorum field was 577 ㎎/㎏ and the content of available P2O5 was slightly lower than the average value.

Table 2. Soil properties as cultivated year of P. grandiflorum

Sample pH
(1:5)
E.C
(dS/m)
O.M
(g/㎏)
T-N
(㎎/㎏)
Avail. P2O5
(㎎/㎏)
Exch. Cations (cmolc/㎏)
K Ca Mg Na C.E.C
2Y-NT-H 4.61ez 0.18a 20.59b 688a 229c 0.34a 6.56a 1.17ab 0.45a 10.86a
5Y-T-H 6.35a 0.24a 25.04a 866a 246c 0.20ab 5.91a 1.10ab 0.29b 5.65b
6Y-T-H 5.77a 0.20a 22.65ab 927a 503a 0.30ab 6.62a 1.20a 0.34ab 9.04ab
11Y-T-H 4.79d 0.13a 21.53b 907a 491a 0.28ab 6.11a 1.01b 0.29b 11.38a
15Y-T-H 5.25b 0.18a 20.10b 781a 438b 0.27b 6.41a 1.09ab 0.28b 9.02ab
zMeans followed by same letter in column are not significantly different at the 5% level according to DMRT (Duncan’s multiple range test).

As a result of C.E.C survey, 11Y-T-H was the highest at 11.38 cmol/㎏ and the 5Y-T-H was the lowest at 5.65 cmol/㎏.

The increase of C.E.C in the soil can be used to understand the degree of exchangeable cation capacity, so that the content of the exchangeable cation K, Ca, Mg and Na are also affected. In this study, the content exchangeable cations K, Ca, Mg and Na decreased with the decrease of C.E.C from 2 years cultivated field to 5 years cultivated field, and it was confirmed that content of exchangeable cations also increased with the increase of C.E.C in 6 years cultivated field.

Jung et al. (1996) reported that average contents of exchangeable cation K, Ca and Mg were 0.43, 4.5, and 0.8 cmol/㎏ in survey about soil chemistry of the cultivated area of the medicinal plants in Korea. When the results of the contents of exchangeable cation of the cultivated soil of field examined in this study were compared, the exchangeable cation K content was in the range of 0.27~0.34 cmol/㎏, which was lower than the reference value in the previously cited-study, while the exchangeable Ca and Mg contents were 5.91~6.62 cmolc/㎏ and 1.01~1.20 cmolc/㎏, respectively, the content of which were higher than the reference result.

Soil chemistry by transplanting of P. grandiflorum

Soil chemical properties as affected by transplanting P. grandiflorum were analyzed on 5Y-NT-H (cultivated for 5 years, non transplanted) and 5Y-T-H (cultivated for 5 years, transplanted) (Table 3).

Table 3. Soil properties of trans planting for 5 years of cultivation of P. grandiflorum

Sample pH
(1:5)
E.C
(dS/m)
O.M
(g/㎏)
T-N
(㎎/㎏)
Avail. P2O5
(㎎/㎏)
Exch. Cations (cmolc/㎏)
K Ca Mg Na C.E.C
5Y-NT-H 5.01bz 0.14b 26.02a 794a 58b 0.23b 5.91a 0.91a 0.20b 8.47a
5Y-T-H 6.35a 0.24a 25.04a 866a 246a 0.20a 5.91a 1.10a 0.29a 5.65b
zMeans followed by same letter in column not are significantly different at the 5% level according to DMRT (Duncan’s multiple range test).

O.M content, T-N, and exchangeable Ca content were not significantly different depending on transplanting in cultivated P. grandiflorum for 5 years. However, in the case of C.E.C, it was confirmed that 5Y-NT-H was 5.65 cmolc/㎏ and 5Y-T-H was 8.47 cmolc/㎏. In the case of available P2O5 content, 5Y-NT-H was 82 ㎎/㎏, which was significantly different from 246 ㎎/㎏ of 5Y-T-H. This has shown that it is possible to overcome the available P2O5 decrease in soil condition for the growth of the P. grandiflorum through transplanting like the results of soil properties by cultural years of P. grandiflorum. However, it is considered necessary to prepare for the reduction or loss of available P2O5 which may occur during long term cultivation. Since cultivation of P. grandiflorum is continuously performed at the same place, it will have a great influence on the maintenance of available P2O5 in the soil.

Soil chemistry by occurrence of root rot disease of P. grandiflorum

In order to compare the soil chemical properties by as affected by the occurrence of root rot disease in cultivated years, soil chemical characteristics were analyzed on healthy plant and diseased plant in all cultivated years in study (Table 4).

In the case of E.C, the result of 2Y-NT-H (cultivated for 2 years, healthy plant) was 0.18 dS/m while for 2-NT-D (cultivated for 2 years, diseased plant) it was 0.11 dS/m. The T-N contents of 2Y-NT-H was 688 ㎎/㎏ and 2Y-NT-D was 977 ㎎/㎏, significant difference was confirmed between the two soils, but there was no significant difference in the other analysis items. It is thought that this is due to the fact that the cultural period of P. grandiflorum is short and the consumption of the chemical composition of the soil is not large. In the case of pH, in all cultural years, soils of healthy plant and diseased plant were distributed in the acidic range with 2Y-T-H as the most acidic at pH 4.61. It was also found that the soil pH of a cultivated land with diseased plants was lower than the soil pH of where healthy plants were grown in all cultivated years in study.

Table 4. Soil properties affected by root rot disease of P. grandiflorum

Sample pH
(1:5)
E.C
(dS/m)
O.M
(g/㎏)
T-N
(㎎/㎏)
Avail. P2O5
(㎎/㎏)
Exch. Cations (cmolc/㎏)
K Ca Mg Na C.E.C
2Y-NT-H 4.61az 0.18a 20.59a 688b 229a 0.34a 6.56a 1.17a 0.45a 10.86a
2Y-NT-D 4.63a 0.11b 22.20a 977a 244a 0.32a 6.06a 1.10a 0.36a 9.90a
5Y-NT-H 5.01b 0.14b 26.02b 794b 58b 0.23b 5.91a 0.91b 0.20a 8.47a
5Y-NT-D 6.04a 0.35a 32.87a 1048a 112a 0.27a 6.07a 1.04a 0.25a 7.37b
5Y-T-H 6.35a 0.24a 25.04a 866a 246a 0.28b 5.94a 1.10b 0.29a 5.65b
5Y-T-D 6.49a 0.26a 18.80b 688b 172b 0.33a 6.61a 1.23a 0.31a 7.29a
6Y-T-H 5.77b 0.20a 22.65a 927b 503a 0.30b 6.62a 1.20a 0.34a 9.03a
6Y-T-D 5.92a 0.23a 22.80a 1105a 519a 0.35a 6.19a 1.19a 0.45a 6.98b
11Y-T-H 4.79b 0.13b 21.53a 907a 491a 0.28a 6.11a 1.01a 0.28a 11.38a
11Y-T-D 5.31a 0.16a 21.52a 757b 387b 0.26a 5.76b 0.93a 0.21a 8.16a
15Y-T-H 5.25b 0.18b 20.10b 781b 438a 0.27a 6.41a 1.09a 0.28a 9.02a
15Y-T-D 5.55a 0.21a 22.38a 904a 450a 0.30a 5.91a 1.15a 0.30a 8.07a
zMeans followed by same letter in column not are significantly different at the 5% level according to DMRT (Duncan’s multiple range test).

Generally, E.C was found to be higher in diseased plant soil except the one cultivated for 2 years. However, significance was recognized only in healthy plant and diseased plant soil of cultivated for 5 years, 11 years and 15 years areas. In particular, the excess of the exchangeable cation Na affects the E.C increase but in this study, it was confirmed that the exchangeable cation Na content was higher in the exchangeable cation Na content of diseased plant soil than healthy plant soil in all cultural years, but the significance was not recognized.

O.M contents were highest in 5Y-NT-D at 32.87 ㎎/㎏ and O.M of healthy plant and diseased soil of all cultural years was similar to the average O.M content of 25 g/㎏ and correlation with O.M by occurrence root rot in P. grandiflorum was not found (Jung et al., 1996).

In the case of T-N and available P2O5 content, diseased plant soil was higher than healthy plant soil in most cultural years except for those cultivated for 5 years and 11 years, transplanted but T-N was significant. Available P2O5 was not significant.

The contents of exchangeable cation K and Na of diseased plant soil were slightly higher than healthy plant soil but exchangeable cation K was significant only in soils of cultivated for 5 years in both non transplanted and transplanted and soils of cultivated for 6 years, transplanted. In the case of the exchangeable cation Na, no significant difference was found depending on occurrence root rot disease in all cultural years. The exchangeable cation Ca and Mg contents were higher in healthy plant soils than diseased plant soils but exchangeable cation Ca was found to be significant only in soils of cultivated for 11 years, and the exchangeable cation Mg was found to be significant only in transplanted and non transplanted soils of cultivated for 5 years.

C.E.C of diseased plant soils was found to be lower in cultivated years except for those cultivated for 5 years, transplanted soils than healthy plant soils but significance was shown only in cultivated for 5 years transplants and non transplanted soils and in cultivated for 6 transplants and non transplanted soils.

Discussion

Soil chemical properties of 12 soil samples from Okcheon, Chungbuk province were analyzed in August, 2017 in order to determine the soil environmental conditions for stable the long term cultivation and reduction root rot disease of P. grandiflorum which is known as a medicinal resource. The soil pH was distributed within the range of 4.61 to 5.25 at all of cultivated years. E.C (Electric Conductivity) and T-N (Total Nitrogen) at all cultivation years were not significant. Available P2O5 was higher than the 405 ㎎/㎏, average for medicinal crops and 320 ㎎/㎏, the average for P. grandiflorum in Korea as cultivation years. C.E.C (Cation Exchange Capacity) was inconsistent for each cultivation year. In particularly, it was validated that the content of exchangeable cations K, Ca, Ma, and Na in this experiment was similar to that of C.E.C according to the cultivation years, because C.E.C had a high correlation with the exchangeable cations. Soil chemistry by transplanting of P. grandiflorum in this study, showed the distinct difference at available P2O5. 5-NT-H (cultivated 5 years and non-transplanted) had 58 ㎎/㎏, while 5Y-T-H (cultivated 5 years and transplanted) had 246 mg/kg. Thus, measures were required to prevent the loss of available P2O5 when cultivation of P. grandiflorum. In soil chemistry by occurrence root rot disease of P. grandiflorum, the soil pH was found to be lower (acidic) in diseased soils than healthy soils at all cultivation years. E.C was confirmed to be was higher in diseased soils than healthy soils except for the one cultivated for 2 years with a relatively stable soil environment. O.M (Organic Matter) content was distributed within the range of 18.80 g/㎏ to 25.04 g/㎏ found to be within the average (25 g/㎏) of P. grandiflorum in Korea, but correlation between O.M and disease occurrence could not be determined. The contents of T-N and available P2O5 were higher in diseased soil except for the one cultivated for 5 years and 11 years but T-N was significant only. The exchangeable cation K and Na tended to be higher in diseased soils rather than that in healthy soils, but soils of cultivated for 5 years (transplanted and non transplanted) and 6 years (transplanted) were significant only. The exchangeable cation Ca and Mg contents were higher in healthy soils than in diseased soils and the contents were also higher than average (25 g/㎏) of P. grandiflorum in Korea. The C.E.C of the soil was lower than that of healthy soils in all of the years except for the one which was cultivated for 5 years (transplanted). As a result, it is also expected to be necessary to prepare for the reduction of nutrient holding capacity as continuous cropping and transplant of P. grandiflorum for stable long term cultivation of the one.

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