Journal of Agricultural Science and Food Research
Open Access

Productivity of Leafy Green Vegetable Kale in Soilless Cultivation Conditions

Daryadar M^*, Mairapetyan KH, Tovmasyan AH, Aleksanyan JS, Tadevosyan AH, Kalachyan LH, Stepanyan BT, Galstyan HM and Asatryan AZ ^*Correspondence: Daryadar M, GS Davtyan Institute of Hydroponics Problems, National Academy of Science of the Republic of Armenia, Armenia, Tel: +37410527031, Email:

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Introduction

Vegetables take big place in human's food being inseparable part of meals. They have important role in regulation of human's nervous system, digestive and other organs activity; as well they increase organism’s resistance. Especially such said salad vegetables that are used in raw condition without cooking have great value. During recent years non-traditional cultivated plants that already have large demand in consumer market have conquered their specific place in the range of vegetable cultivated plants. The range of such cultivated plants includes the Brussels sprout, pak choi, broccoli and etc. from the cabbage family, which are considered as delicacy cultivated plants, differing from the other kinds of cabbage with their nutritional properties.

Taking into account above mentioned, valuable prospective leafy green vegetable kale was firstly introduced into Armenia by us and it was purposed to study the growing possibility and productivity of this cultivated plant in soilless culture conditions (hydroponics), as well as to detect optimal conditions to receive quality, ecologically more safe plant raw material in the Institute of Hydroponics Problems (IHP).

Experiments were done in experimental modules of water stream hydroponics of IH, as well as in conditions of classical hydroponics (CH) and soil culture.

Materials and Methods

Kale is a biennial vegetable that belongs to the Brassicaceae family. It has green or violet curly leaves that do not form cabbage head [1,2]. Kale is nearer to the wild cabbage with its properties and chemical content. In food there are used mainly its leaves. The plant blooms and gives seed in the next year [3-7].

Kale contains huge amount of proteins equal to meet products (4.3%), all 9 essential amino acids (Val, His, Leu, Lys, Trp and etc.) and 11 non-essential amino acids. In fresh kale leaves the amino acids glutamic acid, proline and aspartic acid are dominant in total amino acid content (12%, 12% and 10%, respectively) [8,9]. The amount of Leu, Lys, Val, Arg and Ala is between 6-8% of total amino acid content and the amount of Tyr, Phe, Thr, His, Ser and Gly is between 3-5% of it. The sulphur containing amino acids cystine (1.6%) and Met (2%) have the lowest proportion [10]. It is rich also with fatty acid omega 3, vitamins (A, C, K, PP, B and etc.), easily digestible Ca (120-150 mg), Mg (34-47 mg) and other mineral substances (K, P, Na, Fe, Zn, Se, Mn, Cu and etc.) [11,12]. Due to content of lutein existed in plant it protects human eye from sun’s ultraviolet rays. Frequent use of this plant in diet protects human organism from a number of diseases, particularly from cardiovascular, gastrointestinal, eye (glaucoma) diseases, diabetes, malignant tumors and etc. [6]. Kale contains 45 different kinds of flavonoids (sulphoraphane, indole-3-carbinol and etc.) that provide the antioxidant and anti-inflammatory properties of this plant, too [9,13-15]. They increase organism’s immunity, decrease the cholesterol level in blood. Regulating glucose level it promotes the decrease of weight. High amount of calcium, contained in the plant (2 times more than in milk) influences on the bone cells generation and regeneration, by that preventing rickets, osteoporosis, teeth fragility. At present kale is widely spread in USA, Western Europe, Japan and in several other countries [16].

The experiments were done in conditions of water stream (cylindrical, gully, continuous), classical hydroponics on the volcanic red slag substrate with the 3-15 mm diameter and in conditions of soil culture with 8 plant/m2 density. Plants’ nutrition was done with Davtyan 0.75 N nutrition solution [4]. In water stream hydroponics the nutrition solution was pumped periodically, irreversibly like a jet during a day about 6-20 times (dependent on climate conditions) with 10-15 second duration to the root-bearing stratum of each plant. The amount of one-time giving solution was 20-50 ml. Plants were nourished 1-3 times during a day in CH and once during 3-4 days in soil culture, maintaining all adopted agro-technical rules (soil aeration, weeds removal, periodic watering, fertilization and etc.) [12]. Leaves harvest was done during June-October.

During vegetation biometric measurements, also bio-pharmacochemical analyses were done. In plant raw material the content of extractive substances, tannins and humidity was determined according SPh XI, flavonoids were identified according Borisov, and vitamin C was estimated according Yermakov [2,17-19]. Techno genic RN (radionuclides) in samples was determined through radiochemical methods with small UMF-1500 background radiometer [14]. The concentration limit values (ACL) have been given according state standards of Russian Federation [8,18] that have been officially accepted also in Republic of Armenia. Received results were statistically analyzed according Dospekhov [5].

Results and Discussion

From the analysis of the data presented in the Table 1 it was revealed that during vegetation in all variants, except continuous hydroponics, maximal output of fresh plant raw material was ensured in July during first harvest. Besides, kale raw material received using different hydroponic systems 1.5-1.8 times exceeded soil culture, at the same time gully and classical hydroponic systems 1.1-1.3 times surpass the experimented other hydroponic variants with the yield, plant height and stem thickness (Figure 1).

Table 1: Fresh mass of kale during vegetation in hydroponics and soil, g/plant.

Figure 1: Biometric data of kale in hydroponics and in soil.

In all hydroponic variants, except continuous hydroponics the maximal accumulation of fresh plant raw material (1.6-2.9 times) was observed in July. It is important to mention that it was noticeably high (2.8-7.0 times) in soil control during first month.

It is necessary to emphasize that growth conditions have significant influence on the pharmaco-chemical indices of plant raw material (Table 2). The increase of extractive substances content (1.2-1.5 times) was stated in all water stream hydroponic modules and relatively high content of flavonoids was established in gully system (10-35%). In hydroponics the content of tannins was fluctuated between 2.0-2.2% that conceded insignificantly the same index of soil (2.4%). It was revealed also the influence of cultivation conditions on the biosynthesis of vitamin C: cylindrical and continuous hydroponic systems exceeded 1.3-1.5 times the conditions of gully, classical hydroponics and soil by the content of vitamin C (Table 2). Due to high crop capacity of hydroponic plants the difference between plants of hydroponic systems and soil is significant from the point of mentioned indices: in the case of extractive substances the difference is 1.7-2.3 times, for flavonoids it is 1.2-2.0 times, in the case of tannins it is 1.2-1.6 times and for vitamin C it is 1.8-2.2 times.

Table 2: The pharmacochemical indices of kale in hydroponics and in soil.

Plant cultivation conditions influenced specifically on the RN accumulation in plant raw material (Table 3). Thus, plants in water stream hydroponics conceded by the content of ⁹⁰Sr and ¹³⁷Cs plants grown as in classical hydroponics (1.2-1.3 and 1.1-1.2 times), as in soil (1.8-2.0 and 1.4-1.5 times) conditions.

Table 3: The content of ⁹⁰Sr, ¹³⁷Cs in kale's plant raw material and RN relative indices in hydroponics and in soil.

In different hydroponic systems the content of ⁹⁰Sr in kale's plant raw material exceeded the content of ¹³⁷Cs in all 1.1-1.2 times and in soil culture it exceeded 1.5 times.

Probably, RN has entered into kale as through the roots from the nutrient solution or irrigation water and soil, as through over ground organs by the out of root way from the air basin (atmospheric precipitations, hydro and aerosols, dust).

Calculation showed that the values of observed ratios (OR) of ⁹⁰Sr-¹³⁷Cs pair for kale in systems of nutrient solution-plant and soil-plant were 0.07-0.08 in hydroponics and 2.1 in soil. That is OR<1, which means that from the nutrient solution the cultivated plants absorbed more intensively ¹³⁷Cs in hydroponics and ⁹⁰Sr in soil (Table 3). It was confirmed through the values of RN accumulation coefficients (OC) of cultivated plants. . For the kale in hydroponics ¹³⁷Cs AC>⁹⁰Sr AC 12.2-13.8 times, and in soil ⁹⁰Sr AC>¹³⁷Cs AC 2 times.

Conclusion

Kale cultivated in different hydroponic systems exceeded with fresh plant raw material and with a number of biochemical indices (vitamin C, extractive substances, flavonoids and tannins) and conceded with radiochemical indicators to the same indicators of soil culture. Modern water stream hydroponic way is radio ecologically more safe biotechnological way for plant raw material production, than classical hydroponics and soil culture. Despite of the cultivation conditions the content of controlled techno genic RN (⁹⁰Sr, ¹³⁷Cs) in kale’s plant raw material did not exceed ACL. Kale production with modeling of the innovation technology of modern water stream hydroponics on hectares may satisfy the demand of our Republic.

References

1. Abbey L, Pham TH, Annan N, Leke-Aladekoba A, Thomas RH (2018) Chemical composition of kale as influenced by dry vermicast, potassium humate and volcanic minerals. Food Res Int 107: 726-737.
2. Borisov MI, Belikov VV, Isakov TI (1975) Quantitative content of flavonoids in such plants as e L., Galium L. Vegetative resources. Biolog J Armenia 9: 351-358.
3. http://academics.hamilton.edu/foodforthought/our_research_files/cabbage_cauliflower_kale.pdf.
4. Davtyan GS (1969) Hydroponics as an industrial achievement of agrochemical science. Publishing House SA of Armenian SSR, Armenia.
5. Dospechov BA (1985) Field experiment method. Agropromizdat, Moscow, Russia.
6. Giacoppo S, Galuppo M, Iori R, De-Nicola GR, Cassata G, et al. (2013) Protective role of (RS)-glucoraphanin bioactivated with myrosinase in an experimental model of multiple sclerosis. CNS Neurosci Ther 19: 577-584
7. https://aggie-horticulture.tamu.edu/archives/parsons/publications/vegetabletravelers/kale.html
8. Ministry of Health of RF (2002) Hygienic requests to the safety and food value of food products. Sanitary-epidemiological rules and norms.
9. Kuntz S, Kunz C (2014) Extracts from Brassica oleracea L. convar. acephala var. sabellica inhibit TNF-a stimulated neutrophil adhesion in vitro under flow conditions. Food Funct Jun 5: 1082-1090.
10. Lisiewska Z, Kmiecik W, Korus A (2008) The amino acid composition of kale (Brassica oleracea L. var. acephala), fresh and after culinary and technological processing. Food Chem 108: 642-648.
11. Mairapetyan SK, Davtyan GS (2007) Institute of Hydroponics Problems of NAS RA in 60 years Communications of IHP NAS RA, Yerevan, pp: 3-16.
12. Mairapetyan SK (1989) Culture of essential oil plants in open-air hydroponics. Publishing House AS of Arm SSR, Yerevan, Armenia.
13. Olsen H, Aaby K, Borge GI (2009) Characterization and quantification of flavonoids and hydroxycinnamic acids in curly kale (Brassica oleracea L. Convar. acephala Var. sabellica) by HPLC-DAD-ESI-MSn. J Agric Food Chem Apr 57: 2816-2825.
14. Pavlotskaya F (1966) Methods of identification of Sr-90 and other long-lived isotopes in soil. Physical-Chemical Methods of Soil Study.
15. Sikora E, Bodziarczyk I (2012) Composition and antioxidant activity of kale (Brassica oleracea L. var. acephala) raw and cooked. Acta Sci Pol Technol Aliment 11: 239-248.
16. Kim SY, Yoon S, Kwon DM, Park KY, Kim YCL (2008) Kale Juice Improves Coronary Artery Disease Risk Factors in Hypercholesterolemia Men. Biomed Environ Sci 21: 91-97.
17. State Pharmacopaea of USSR (1990) Current state and strategy for the future.
18. Supplement of Technical Regulations of Fresh Fruit Vegetable-1913-N Decision (2006) RA Government of Armenia.
19. Yermakov A, Arasimovich A, Smirnov-Ikonnokova M, Murri I (1952) Methods of plants biochemical study.