Comparative analysis of agrochemical, allelopathic and microbiological characteristics of the soil environment for Actinidia arguta (Siebold et Zucc.) Planch. ex Miq. cultivated in Ukraine and two provinces of China

The objective of this study was to evaluate agrochemical, allelopathic and microbiological characteristics of the soil under Actinidia arguta plants cultivated in Ukraine and two provinces of China. Material and methods. The rhizosphere soil was sampled at 0–15 cm layer under A. arguta plants in the stage of fruit ripening in Ukraine (Kyiv city: North of Ukraine, Forest-Steppe zone, a temperate continental climate) and two provinces of China (Shandong: East China, a temperate monsoon zone; and Heilongjiang: Northeast China, continental monsoon climate). The concentrations of carbon, available forms of macroand micronutrients, phenolic compounds in the soil samples were determined. pH and redox potential of soil were measured. Soil phytotoxicity was studied by direct bioassay method on cress (Lepidium sativum) root growth. Microbiological analyses of soil samples were conducted. Results. The dissimilarities in the concentrations of carbon, macroand micronutrients in the examined soil samples were shown. The reduction conditions (Eh < 400 mV) in the soils under A. аrguta might slow down the humification processes. A similar effect may be caused by mobile forms of organic compounds with allelopathic properties. The redox potential decreased with the increase of pH values. This fact reflects the intensifying of reduction processes. The soil phytotoxicity under A. аrguta reached 20–70 % compared with the control, probably due to the accumulation of phenolic compounds, as well as iron and manganese. In soils under A. аrguta, the relationship between pH, phytotoxicity, and the abundance of main taxonomical and ecotrophic groups of microorganisms was evaluated. Conclusions. Calcic Luvisols from the M.M. Gryshko National Botanical Garden of the NAS of Ukraine (Kyiv city, Ukraine) and Luvic Chernozems from Jiamusi (Heilongjiang province, China) were determined to be the most favorable for A. arguta cultivation. Salic Solonetz from Harbin (Heilongjiang province, China) and Haplic Luvisols from Linyi (Shandong province, China) had the least suitable soil conditions for A. arguta.

In particular, in Ukraine, introductory studies with A. arguta were initiated by M. Kaschenko, a member of the Academy of Sciences of Ukrainian SSR, in the Acclimatization Garden (Kyiv) in the 1920s (Skrypchenko & Latocha, 2017). A. arguta has been successfully cultivated since the 1950s in the M.M. Gryshko National Botanical Garden of the NAS of Ukraine, where its anatomical, morphological and biochemical features, regenerative ability under conditions of introduction are investigated, and also selection work is carried out (Skrypchenko, 2002;Skrypchenko & Latocha, 2017).
Investigations of the soil environment of kiwifruit are fragmentary in contrast to its well-studied biological properties (Richards et al., 2007;Li et al., 2017а;Stefaniak et al., 2017b). This fact motivated us to pay attention to the study of the soil properties under A. arguta in the centers of its introduction (Ukraine) and natural habitat (China). We hypothesized that the relations between agrochemicals, allelochemicals, and soil microbiota determine the success of the introduction and cultivation of A. arguta plants. An analytical assessment of the characteristics of the soil under A. arguta plants in Ukraine and the provinces of China will help to determine the optimal conditions for its cultivation. This approach will provide opportunities for the interchange of A. arguta cultivars of local selection in the future.
The objective of this study was to evaluate agrochemical, allelopathic and microbiological characteristics of the soils under A. arguta plants in Ukraine and two provinces of China.

Material and methods
The rhizosphere soil was sampled at 0-15 cm layer under A. arguta plants in the stage of fruit ripening. This stage completes the generative period of development. It is the most important in the ontogenesis of fruit plants, in particular, of A. arguta.
The analysis was conducted on:  (2015).
Air-dry soil samples were sieved using a 1 mm diameter sieve. Available forms of macro-(N, P, K) and micronutrients (Fe, Mn) were extracted with 1M HCl from air-dry soil (Rinkis & Nollendorf, 1982). The concentrations of carbon and nitrogen in the soil samples were determined as described by Rinkis & Nollendorf (1982). Qualitative and quantitative analysis of P, K, Fe, and Mn was performed using Thermo Scientific iCAP 6300 ICP (Inductively Coupled Plasma) Spectrometer. Phenolic compounds were extracted from the soil by desorption method using an ion exchanger KU-2-8 (H + ) (Grodzinskij et al., 1988). The contact of the soil with the resin (KU-2-8 (H + )) was held in a flat-bottomed flask with a ground stopper in a neutral medium (ethyl alcohol) at a ratio of soil : resin : alcohol -1 : 1 : 2. The contents of the flask were well stirred and allowed to contact for 48 hours. After that, the eluates were separated by centrifugation at 6000 rpm for 20 minutes.

Analysis of the soil environment for Actinidia arguta cultivated in Ukraine and China
After removal of the supernatant liquid, the contents of the centrifuge tubes were washed with ethyl alcohol. Then elution continued for 18 hours. Subsequently, the extraction was carried out in the same sequence twice with aqueous acetone (2 : 1 by volume). The eluates were concentrated on a water bath. The dry residues of alcohol and water-acetone eluates were dissolved in 5 ml of 96 % and 10 ml of 48 % ethanol, respectively. The content of phenolic compounds in the obtained alcohol solutions of two eluates (alcohol and water-acetone) was measured spectrophotometrically at 730 nm wavelength using Folin-Ciocalteu reagent. The total amount of phenolic compounds was expressed as gallic acid equivalent.
Soil phytotoxicity was studied by direct bioassay method on cress (Lepidium sativum L.) root growth (Grodzinskij et al., 1990). The redox potential (Eh) was measured in soil suspension, as a model of soil solution, at the soil to distilled water ratio as 1 : 1 by potentiometric technique (Fiedler et al., 2007;Labuda & Vetchinnikov, 2011).
To determine the ratio between the separate ecotrophic groups, we calculated the mineralization-immobilization coefficient, following the methods of Andreiuk et al. (2001), and the calculation of SOM (soil organic matter) transformation index was based on Mukha (1980).
A one-way analysis of variance (ANOVA) was performed to determine the effect of factors such as pH and phytotoxicity on agrochemical, allelopathic, and microbiological characteristics of the soil. The probability of influence factors was estimated by the significance level (P) and Fisher's test (F). The data presented in the tables and figures are averages and standard deviation of the mean (SD). Five replicates were used in each treatment. Experimental data were statistically analyzed using Statistica 10.0 and Microsoft Excel software.

Results and discussion
The investigation of the soil samples under hardy kiwifruit indicates various carbon concentrations in the different habitats. The lowest value of carbon concentration was detected in Haplic Luvisols from Linyi (Table 1). Salic Solonetz from Harbin contained 2.5 times more carbon than Haplic Luvisols. The carbon concentration was higher in Luvic Chernozems from Jiamusi and Calcic Luvisols from NBG (Kyiv).
Soil with the pH 5.5-6.0 is suggested to be the best for the hardy kiwifruit cultivation (Strik, 2005  As one of the vital nutrients, potassium is essential for the soil water regime. A. arguta was reported to be rich in potassium (Latocha, 2017). Haplic Luvisols from Linyi was characterized by 1.7-3.3 times lower concentration of potassium as compared to the rest of the analyzed soil samples. Moreover, the content of this nutrient was probably affected by the soil texture. Сlay, loam, and heavy sandy-loam soils tend toward higher levels of potassium than sandy and sandy-loam ones.
Relationships between pH and soil-forming environmental factors (climate, parent material, and topography) in Southwestern China were previously observed (Zhang et al., 2019). Soil pH affects the mobility and bioavailability of nutrients, microbiological activity, plant growth, and development (Neina, 2019). Therefore, we analyzed the relationships between soil pH and agrochemical, microbiological and allelopathic characteristics of the studied soils. Results of the analysis of variance (ANOVA) showed that pH factor significantly affected the soil agrochemical characteristics such as the concentrations of phosphorus, iron, and manganese (Table 2). Phosphorus concentration prevailed in Haplic Luvisols from Linyi. At the same time, low pH reduced the availability of several nutrients, particularly phosphorus. The highest level of iron was in Luvic Chernozems from Jiamusi. The maximum concentration of manganese in Haplic Luvisols from Linyi was observed. Low pH values raised the solubility of toxic forms of iron and manganese, which can have an unfavorable impact on plant growth and development.
The biochemical state of the soil was evaluated by the values of the oxidationreduction potential (redox potential or Eh). Soil Eh is dynamic and dependent on many factors, i.e., aeration, temperature, humidity, organic matter, the enzyme activity of microorganisms (Husson, 2013). Redox potential is used as an indicator of the content of biogenic forms and toxins in the soil environment (Husson, 2013).
It was shown that the reduction processes of different intensity levels were dominant in soil samples under A. arguta. The pH factor contributed to the change in the Eh values  Analysis of the soil environment for Actinidia arguta cultivated in Ukraine and China (Table 2). Moreover, the redox potential decreased with the increase of pH values (Fig. 1). This fact reflects the intensifying in reduction processes. Thus, the maximum reduction was recorded in the soil from Harbin, which was characterized by an alkaline reaction. The observed tendency was also described for other types of soil (Husson, 2013). The observed reduction conditions (Eh < 400 mV) in the investigated soils indicated a slowdown in the humification process. It also may reflect the presence of mobile forms of organic compounds that can be involved in allelopathic interactions. Phenolic compounds are considered to be one of the essential classes of allelochemicals. They are widespread in the plant world and have versatile effects on crucial physiological and biochemical processes such as respiration, photosynthesis, growth, and development (Li et al., 2010).
Therefore, we considered it necessary to investigate the concentration of phenolic compounds in the rhizosphere soil of A. arguta. The investigated soils differed in the concentration of phenolic compounds (Fig. 2). Their lowest concentration was determined in the soil from M.M. Gryshko National Botanical Garden. In the soils from Harbin and Linyi, the total concentration of phenolic compounds prevailed. It should be noted that these soil samples were characterized by the lowest carbon content ( Table 1).
The accumulation of free phenolic compounds was due to a violation of the humification process. At the same time, the dominance of intensively reducing conditions in the soil from Harbin contributed to the formation of the highest amount of organic substances with phenolic groups.
The soil phytotoxicity under the plants of A. arguta reached 20-70 % compared to the control (Fig. 3). It was the smallest for Calcic Luvisols from NBG and the largest for Salic Solonetz from Harbin.
Soil phytotoxicity factor showed the most substantial effect on the concentrations of phenolic compounds, iron, and manganese ( Table 3). The effect of the phytotoxicity factor was the greatest concerning the accumulation of phenolic allelochemicals.
The soil microbiota provides the decomposition of the complex organic compounds into the nutrients available for plants (Li et al., 2017b). Consequently, the study of microbiocoenosis allows to understand the direction of microbiological processes and to predict changes in soil conditions, which can be used to create and to improve crop cultivation techniques. In turn, these benefits sustain the conservation and remediation of soil fertility as the prerequisite for good productivity of the whole agro-ecosystem. Chinese researchers observed that soil treatment with beneficial microbiota increased the kiwifruit yield and enhanced the crop resistance for diseases (Li et al., 2017а). Nevertheless, there is no data about the abundance of main taxonomical and ecological trophic groups of microbiota as well as the direction of microbiologic processes in soils under A. arguta. pH factor significantly influenced the abundance of micromycetes (Table 2). Among the samples from the several Chinese provinces, Haplic Luvisols from Linyi was characterized with the highest abundance of micromycetes (Table 4). Therefore, this trend was the consequence of the lowest pH (4.2) of the corresponded plot (Table 1).  Analysis of the soil environment for Actinidia arguta cultivated in Ukraine and China Luvic Chernozems from Jiamusi with weakly acid reaction was rich in soil fungi, and Salic Solonetz from Harbin with weakly alkaline reaction was deficient in them (Fig. 4). Soil samples from NBG outstood with the lowest abundance of this microbiota group, but the higher level of actinomycetes as compare with Chinese samples (Fig. 5). Among the studied groups of microbiota, the abundance of micromycetes was the most sensitive to soil phytotoxicity (Table 3). Ammonifiers showed the least response to soil phytotoxicity.
It was observed the slight difference of ammonifier abundance between the analyzed samples. The soil from Harbin was the poorest, and from NBG was the richest in this group of the microbiota. At the same time, nitrogen   Table 4. The abundance of the main taxonomical and ecotrophic groups of microbiota in soils under Actinidia arguta plants.
immobilizing microbiota was 1.5 times more abundant in Luvic Chernozems from Jiamusi, and 2.0 times -in Calcic Luvisols from NBG, as compared with the rest analyzed soil types. Luvic Chernozems from Jiamusi and Calcic Luvisols from NBG exhibited the amplification of the processes of SOM mineralization. Altogether, the low values of the SOM transformation index can be the result of the input of organic matter in soils on insignificant levels.

Conclusions
The dissimilarities in the concentrations of carbon, macro-and micronutrients, phenolic allelochemicals, Eh values, and abundance of soil microbiota in the examined soil samples were shown.
The results of the analysis of variance (ANOVA) showed that the investigated factors such as pH and phytotoxicity significantly influenced the agrochemical, allelopathic and microbiological characteristics of the soils under A. arguta soil. pH factor affected Analysis of the soil environment for Actinidia arguta cultivated in Ukraine and China Eh, the abundance of micromycetes, the concentrations of phosphorus, iron, and manganese. Soil phytotoxicity factor showed the most potent effect on the concentrations of phenolic compounds, iron, and manganese. The relationship between the phytotoxicity and the abundance of the main taxonomical and ecotrophic groups of microbiota in soils under A. arguta was ascertained. Among the analyzed soil samples, carbon concentration was the highest in Luvic Chernozems from Jiamusi and Calcic Luvisols from NBG. The reduction conditions (Eh < 400 mV) in the soils under A. arguta might slow down the humification processes. A similar effect may be caused by mobile forms of organic compounds with allelopathic properties. The redox potential decreased with the increase of pH values. In the soils from Harbin and Linyi, the total content of phenolic allelochemicals prevailed. Salic Solonetz from Harbin contained the lowest phosphorus concentration among the tested samples.
Meanwhile, the highest level of iron was in Luvic Chernozems from Jiamusi. In Haplic Luvisols from Linyi, the maximum concentration of manganese was observed. Low pH values increase the solubility of toxic forms of iron and manganese, which can adversely affect plant growth and development. The soil phytotoxicity under the plants of A. arguta reached 20-70 % compared to the control.
It was the lowest for Calcic Luvisols from NBG and the largest for Salic Solonetz from Harbin.
Overall, Calcic Luvisols from NBG and Luvic Chernozems from Jiamusi were determined to be the most favorable conditions for the A. arguta cultivation. Salic Solonetz (Harbin) and Haplic Luvisols (Linyi) were less suitable for A. arguta plants. Perspective is further research aimed at developing measures to improve the soil conditions for A. arguta plants.