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ISSN : 1598-5504(Print)
ISSN : 2383-8272(Online)
Journal of Agriculture & Life Science Vol.54 No.4 pp.7-15
DOI : https://doi.org/10.14397/jals.2020.54.4.7

Relationship between Soil Properties and Fruit Yield of New Actinidia arguta (Siebold & Zucc.) Planch. ex Miq. Cultivars in South Korea

Si-Young Ha, Ji-Young Jung, Jai-Hyun Park, Jae-Kyung Yang*
Division of Environmental Forest Science/Institute of Agriculture and Life Science, Gyeongsang National University, Jinju, 52828, Korea
*Corresponding author: Jae-Kyung Yang Tel:
+82-55-772-1862 Fax: +82-55-772-1869 E-mail:
jkyang68@gmail.com
March 4, 2020 June 4, 2020 July 15, 2020

Abstract

Soil properties are important environmental conditions affecting fruit quality and yield in new cultivars of Actinidia arguta. The yield of three A. arguta cultivars (cv. Autumn Sense, cv. Chungsan, and cv. Greenball) from Wonju city, South Korea was investigated from 2017 to 2019 and the relationships to soil properties are discussed. The yield of cv. Autumn Sense, cv. Chungsan, and cv. Greenball fruits ranged from 6.8 to 24.5, 14.0 to 29.0, and 10.5 to 38.5 kg/vine. cv. Autumn Sense had the highest soil organic matter content and soil C/N ratio over the three-year period. The yield of A. arguta fruits was positively correlated with soil C/N ratio and could be described by a power model (y = axb ), suggesting that soil C/N ratio plays an important role in limiting the bioavailability and bioaccumulation of organic matter in A. arguta fruits. In addition, C/N ratio in the soil was influenced by the soil available phosphate. However, the threshold of the C/N ratio for A. arguta fruit differed according to cultivar, and especially the lowest threshold was observed in cv. Chungsan. Therefore, the application of an appropriate C/N ratio depending on the cultivar is required for improved fruit yield. Our results present the soil properties required to increase the yield of the new A. arguta cultivars in South Korea.

초록


    Korea Forest Service
    FTIS2017091C101919AB01

    Introduction

    Kiwifruit is the main representative of Actinidia. It is well-known worldwide and is highly appreciated for its delicious taste and health-promoting properties (Ferguson et al., 2003). Actinidia arguta (Actinidiaceae), commonly known as kiwi arguta, baby kiwi, mini kiwi, kiwiberry, or hardy kiwi, is an abundant seasonal fruit in Asia that has recently been introduced in Europe. This exotic species is very interesting and promising given the horticultural advantages it has over kiwifruit, especially its high frost hardiness (down to -30℃ in midwinter) and relatively short vegetation period (Debersaques et al., 2015). A. arguta is indigenous to Siberia, Japan, North East China, and South Korea. It is commercially produced in New Zealand, British Columbia in Canada, and in Oregon, Washington, Pennsylvania, and New York in the USA. South Korean A. arguta was registered for cultivars in 2006, with cv. Autumn Sense registered in 2013, cv. Chungsan in 2014, and cv. Greenball in 2008. The fruit of cv. Autumn Sense, cv. Chungsan, and cv. Greenball weigh 19.9 g, 19.0 g, and 15.9 g, respectively, and the sugar content is 19.5, 19.0, and 20 brix, respectively. cv. Autumn Sense is a deciduous broad-leaved vine plant. The flowering period is early harvest in May and early in September. The fruit is big, and the sugar content is very high, approximately 19–20 brix. cv. Chungsan, harvested in mid-August, has a large fruit with a sugar content of 15–16 brix. The fruits are grape-like with a variety of sweet fruits. Among the A. arguta varieties, cv. Greenball has a maximum sugar content of 20 brix, which is sweeter than seedless green grapes (Shinemuscat) or peaches.

    According to the International Kiwifruit Organization (IKO) a total annual production of about 2.4 million tons is estimated; however, the hardy kiwi accounts for only 0.2–0.3% of the total world production of fresh fruit (Ferguson, 2015). Furthermore, only three species have commercial importance: A. deliciosa (green kiwi), A. chinensis (yellow kiwi), and recently, A. arguta (baby kiwi) (Debersaques and Mekers, 2010). There have been several studies on the yield and size of A. arguta fruit, and recent studies have been conducted on the yield of A. arguta according to the soil properties in each region (Li et al., 2017). SteFaniak et al. (2017) reported that the average number of shoots was significantly influenced by both soil N and cultivar. Costa et al. (1997) also reported increases in number of shoots of kiwifruit when more N was applied. In related studies, Pailly et al. (1995) observed high abundance of kiwi fruit in soils with high concentration of magnesium. Worthington (2001) reported significantly more vitamin C, iron, magnesium, and phosphorus and significantly less nitrates in kiwi fruit from soil with high organic matter content. Montanaro et al. (2009) reported that the organic carbon content of the soil increases the yield of kiwi fruit. However, studies on soil properties and yield of fruit were mostly performed on Ananasnaya and Hayward of Oregon, USA, or Weiki and Geneva of New Zealand.

    The variety in cultivars and expansion in arable farming has highlighted the need for more specific information related to factors that affect A. arguta yield in the region. It is important to evaluate the soil properties promoting high yield in new cultivars because the differences in properties of A. arguta fruit depend on the cultivar.

    In this study we used yield data of A. arguta and sampled soil relatively comprehensively to study soil properties-yield relationships at the field scale. The objective of the study was to test the hypothesis that soil information is useful for explaining variability in yield at an agricultural field scale.

    Materials and Methods

    1. Experimental site

    The experimental site, Wonju city, is located in South Korea (34°27.044′–37°27.054′ N, 126°55.466′–127°53.174′ E). Climate in this area is temperate with an average annual rainfall of 1279–1311 mm and average annual temperature of 10.8–11.6 ℃. Plant materials investigated were 10- to 15-year-old cv. Autumn Sense, cv. Chungsan, and cv. Greenball A. arguta vines. Fig. 1 shows the fruit of each cultivar. Autumn Sense is long and oval, the shoulder area of the neck is square, and the weight is 19.9 g. The clearing is cylindrical and heavy, weighing 15 g. cv. Greenball has a bovine with a round shoulder shape and a fruit size of 10–11 g. Above-ground drip irrigation was used to supply moisture and A. arguta vines were arranged with a spacing of 1 m. All cultivars received similar horticultural practices and disease and insect control measures.

    2. Soil analysis

    Soil temperature and moisture were measured on site using portable measuring instruments. Soil samples (one composite sample per orchard) were collected during the harvest season (September) for three years (2017–2019). Each composite soil sample (500–1000 g per sample) comprised three sub-samples per experimental site collected from a depth of 0–30 cm near the root of the vine. The soil was sampled at three spots per vine and the physical and chemical properties were analyzed using three replicates per spot. Twenty-seven vines per cultivar were randomly selected for sampling. After air drying for 24 h, the soil samples were gently ground, sieved (2 mm), and stored properly for analysis (Peng et al., 2011). The pH and electrical conductivity (EC) were analyzed in a 1:5 (v/v) water extract and measured using a pH meter (HI8418, HANNA, USA) and an EC meter (LQ2-LE, Vernier, China), respectively (European Standard 13037, 1999). All samples were analyzed for total organic matter using the dry combustion method at 540 ℃ (Nelson and Sommers, 1982). Available phosphate was extracted with water or CaCl2 and measured using an UV spectrophotometer at 720 nm. Available Si was extracted with monocalcium phosphateacetic acid and determined using the simple turbidimetric method based on the formation of BaSO4 precipitate in colloid form and measured using an UV spectrophotometer at 700 nm (Zhang et al., 2017). The C and N concentrations were analyzed by Kjeldahl digestion (Bremner and Mulvaney, 1982) using a macro elemental analyzer (vario MACRO cube, USA). The C/N ratio was calculated that the C and N concentrations.

    3. Yield and fruit size of A. arguta fruit

    Yield was measured immediately after harvest in September during 2017 to 2019 and weighed using scales (GL 6000S, G TECH international, South Korea). The yield was measured in a total of 27 vines per cultivar. Data are expressed as kg/vine in fresh weight. Fruit size was determined at harvest (September 2017 to 2019). A total of 20 fruit per vine were collected and analyzed from 27 A. arguta vines per cultivar. The length, width, and thickness of fruit were determined using digital calipers and immediately assayed after being brought to our laboratory.

    4. Statistical analysis

    Mean and standard deviation were calculated using Microsoft Excel (Microsoft, WA, USA). We performed the Pearson's correlation analysis to identify the relationships between the soil properties and yield of cv. Autumn Sense, cv. Chungsan, and cv. Greenball vines. The Pearson’s correlation coefficient matrix was calculated using R 3.4.3 (Systat Software Inc., CA, USA). In this study, the relationship between the A. arguta fruit yield and the coefficients of the best suitable model was also determined. In order to determine the most suitable model for A. arguta fruit yield, Marquardt-Levenberg non-linear optimization method, using the computer program “curve Expert 3.1” was used.

    Results and Discussion

    1. Properties of soil

    In this study we presented the soils into seven properties based on the three cultivar species and their corresponding properties are listed in Table 1. The soils were slightly acid, with pH values of 6.3–6.9 in 2017 and decreased from 2017 to 2019. The optimum soil pH for hardy kiwi Hayward is between 5.5 and 6.0. Vines show poor growth at a soil pH above 7.2 (Strik and Cahn, 2000). It is not known if other species differ in soil pH requirements, especially, the optimal soil pH for the various cultivars of A. arguta has not been reported. Commonly, fruit do not like strong acid soils, because in soils of pH 5.0 or less, serious problems may arise such as excessive solubility of Al and Mn, or low availability of P, Ca, Mg, and Mo (Chapman, 1968). None of the experimental sites had a soil pH of 5.0 or less. Although the soil in all experimental sites in this study was found to be in the correct pH range for kiwi growth, under natural conditions, soils acidify very slowly over a period of hundreds to millions of years (Guo et al., 2010). Therefore, in the future, proper pH adjustment will be required. The EC of the soils ranged from 44.4 to 56.7 μS/cm in 2017 and increased from 2017 to 2019, in contrast to soil pH. EC indicates the amount of soluble salts (cations or anions) in the soil (Friedman, 2005). Therefore, the highest soil EC values in the soil suggests that there is the largest amount of inorganic substances available to the kiwifruit vines at this site. Si content in soil varied greatly, from 30.2 to 86.7 mg/kg, which was similar to the recommended values (mean 30 mg/kg) for kiwi production in China (EMC, Environmental Monitoring of China, 1990). However, some soil samples contained available Si exceeding the Chinese national standard limit for dry land (40 mg/kg with pH 6.5; State Environmental Protection Agency, 1995). Depending on the parent materials, the soils of Autumn Sense had significantly higher available Si (mean 86.7 mg/kg) than that of the other cultivars (mean 34.1 mg/kg and 62.5 mg/kg) (Table 1). The labile fraction of available Si in soil was generally low because Si in soil is mainly present as insoluble arsenate. There were no obvious relationships between the available Si and the available phosphate, suggesting that the amount of available Si is independent of the available phosphate Autumn Sense had the highest soil organic matter content and soil C/N ratio during the study period (2017 to 2019). These findings are consistent with previous results reported in literature (Agbede et al., 2008). Shahzad et. al. (2015) reported that high organic content increases nitrogen loss in soil. Therefore, it is considered that Autumn Sense had relatively high soil C/N ratio as the ratio of nitrogen loss increases owing to the high soil organic matter content. Furthermore, a high soil organic matter content can also indicate an increase in microbial biomass with a positive relationship seen between organic matter content and bacteria and fungus (Frey et al., 1999).

    2. Fruit yield and size properties

    The range in yield of cv. Autumn Sense, cv. Chungsan, and cv. Greenball fruit was 6.8–24.5, 14.0–29.0, and 10.5–38.5, respectively, over the three years (Table 2). In cv. Chungsan, the yield decreased gradually from 2017 to 2019. We found that the same cultivar differed in fruit yield and size; in particular, the difference in yield of fruit per vine was very significant. Thus, our study showed significant differences in fruit size and yield in A. arguta within the same cultivar. It is supposed that environmental factors such as soil properties were responsible.

    3. Effects of soil properties on A. arguta quality (yield, length, width, thickness) characteristics

    The cross-correlation matrix comprised seven soil properties and four fruit properties (Table 3). There was a strong positive correlation between soil pH and soil EC (r = -0.84 and r = 0.65) in cv. Autumn Sense and cv. Greenball. Available Si and available phosphate content in soil were highly positively correlated (r = 0.89) in cv. Autumn Sense. Especially, the correlation between soil pH and soil organic matter content had the highest correlation (r = 0.89) in cv. Autumn Sense. The highest correlation between soil temperature and soil pH (r = 0.88) was in cv. Chungsan. The highest correlation between soil temperature and soil organic matter content (r = 0.90) was observed in cv. Greenball. Soil correlations were found to vary among varieties. Yield of cv. Autumn Sense and cv. Greenball fruit was strongly related with soil C/N ratio (r = 0.55 and r = 0.60, respectively). Yield of cv. Chungsan fruit was strongly related with content of available Si in soil (r = 0.87). The yield of all three cultivars was found to have the highest correlation with fruit length. These relationships between A. arguta fruit yield and soil organic matter, available phosphate, available Si, and C/N ratio were more significant when fit using an exponential model (y = axb) (Fig. 2). In addition, fruit yield was positively correlated with the soil C/N ratio.

    4. A. arguta fruit yield prediction model using C/N ratio of soil

    The Fig. 3 the predicted A. arguta fruit yield using measured yields and associated soil property. At this time, the soil property was taken from the C / N ratio data, which was positively related to the fruit yield in Fig. 2. Evidence from A. arguta harvesters, as well as personal observation, suggests that the relationship between soil C/N ratio and fruit yield is not linear: vine in soil of 5-10 C/N ratio produce relatively more fruit than 10-15 C/N ratio soil. There is no doubt that examples of vine with high C/N ratio soil can produce high yields of more than 35 kg/vine but it appears, both from anecdotal evidence and from the results of this survey that yields do not increase in a linear fashion. A ‘Curve Expert’ package was applied to test this hypothesis. It was found that as C/N ration of soil increases so yield improves relatively slowly. The best fit curve produced a concave curve, describing a non-linear relationship between C/N ratio of soil and fruit yield (Fig. 3). The cv. Autumn sense, cv. Chungsan and cv. Greenball were fitted the Rational Model, Sinusoidal Model and Sinusoidal Model, respectively. cv. Autumn sense was presented that the with this curve formula applied there was an improved correlation coefficient, 0.79, compared with simple (linear) correlation of 0.29. cv. Chungsan was presented that the with this curve formula applied there was an improved correlation coefficient, 0.73, compared with simple (linear) correlation of 0.06. cv. Greenball was presented that the with this curve formula applied there was an improved correlation coefficient, 0.73, compared with simple (linear) correlation of 0.34. The curve of cv. Autumn sense was defined as y= (a+bx)/(1+cx+dx2) where; y=yield; a= 3.432881; b= -0.229637; c= -0.118437; d= 0.003447; x= C/N ratio. The curve of cv. Chungsan was defined as y= a+bcos (cx+d) where; y=yield; a= 20.432038; b= 4.879158; c= 0.658237; d= -4.338481; x= C/N ratio. The curve of cv. Greenball was defined as y= a+bcos (cx+d) where; y=yield; a= 23.714219; b= 9.491199; c= 0.507531; d= -1.729286; x= C/N ratio.

    From these results, the difference in the C/N ratio affecting the A. arguta fruit yield according to the cultivar became clear. In conclusion, different C/N ratio of soil should be applied for A. arguta fruit yield.

    Davidson et al. (1998) reported a similar negative correlation between soil pH and content of available Si in soil in a kiwi orchard. Soil EC is influenced by a combination of physico- chemical properties including organic matter (Corwin and Lesch, 2005). Soil EC was most strongly correlated with soil organic matter content (r = 0.78) in cv. Autumn Sense; this is consistent with the results reported by Vågen et al. (2006). Previous studies have shown that the physical and chemical properties of soil played a role in fruit yield (Wang et al., 2012). Our finding that yield was negatively related to soil EC, is consistent with previous results obtained for kiwi fruit (Awasthi and Nauriyal, 1972;Munshi et al., 1978). Costa et al. (1997) reported that the soil N was strongly correlated with kiwi fruit yield which is consistent with our result that soil C/N ratio and yield are strongly correlated. Mesfine et al. (2005) reported that the increased grain production in corn and soybean was mainly because of increased available phosphate in soil, and we observed a similar relationship in cv. Greenball, although it was a comparatively low positive correlation. Organic matter, available phosphate, available Si, and C/N ratio should be monitored for improved A. arguta fruit yield. Yield in the A. arguta fruits increased notably with increasing soil C/N ratio (Fig. 2) implying that the bioavailability of soil C/N was strongly affected by the ratio of soil C/N. As seen in the Fig. 2, there appears to be a certain threshold value that limits soil C/N bioaccumulation in A. arguta. When the soil C/N ratio was lower than a certain value (at a conservative estimate from Fig. 2), the bioavailable soil C/N would be high owing to the weak competition between soil C/N on roots and on surfaces of oxides (Fitz and Wenzel, 2002), whereas an elevated soil C/N ratio in the soils led to a significant improvement in fruit yield. C/N ratio higher than the threshold value (4.5) in soils would enhance the yield of A. arguta fruits by at least 6-fold. Therefore, the concentrations of the C/N ratio can be considered as a threshold value to predict yield in the A. arguta crop. Among the cultivars of A. arguta, yield was maintained at relatively low levels which were not correlated with the available Si concentrations in soil, except in cv. Chungsan (Table 3 and Fig. 2). This is because most of the soils where the A. arguta was grown have lower available Si concentrations than the threshold values mentioned above (Fig. 1), making Si unavailable to the A. arguta fruit. However, the threshold C/N ratio for A. arguta fruit was different among cultivars, and especially, cv. Chungsan showed the lowest threshold. Therefore, the application of the appropriate C/N ratio depending on the cultivar for improved fruit yield is required.

    This study showed that the yield in the A. arguta fruits from the three cultivars, cv. Autumn Sense, cv. Chungsan, and cv. Greenball, was different, and therefore, these results can be considered as background values for comparison in future studies. The yield in A. arguta fruit depended on soil organic matter, available phosphate, available Si, and C/N ratio. The C/N ratio higher than the threshold value (4.5) in soils would enhance the yield of A. arguta fruits by at least 6-fold. The C/N ratio was found to be influenced by the available phosphate in soil, and the maximum yield of A. arguta was in soils with a temperature range of 20.1–22.6 °C. We hope that this result will be useful information for ensuring optimal soil conditions to promote a high yield in the new cultivars of A. arguta in South Korea.

    Acknowledgements

    This study was carried out with the support from the “R&D Program for Forest Science Technology (Project No. "FTIS 2017091C101919AB01)” provided by the Korea Forest Service (Korea Forestry Promotion Institute).

    Figure

    JALS-54-4-7_F1.gif

    A.arguta cultivar in this experiment (A: Autumn sense; B: Chungsan; C: Greenball).

    JALS-54-4-7_F2.gif

    Relationship between A. arguta yield and soil available phosphate, available Si, organic matter and C/N ratio.

    JALS-54-4-7_F3.gif

    Fruit yield prediction model based on C/N ratio of soil for various cultivar. (A: cv. Autumn sense; B: cv. Chungsan; C: cv. Greenball).

    Table

    Chemical properties of A. arguta orchard produced over a cultivars and year

    Yield and fruit size (length, width and thickness) in response to A.arguta fruit of various cultivar

    Correlation matrix identifying significant relationships between A. arguta fruit yield, A. arguta fruit size and soil properties

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