Jpn. J. Trop. Agr. 51(3) : 84-94, 2007 Effect of Concentrations of Nutrient Solutions in Aeroponic and Drip Irrigation Systems on the Growth of Touki, Angelica acutiloba Kitagawa Ninh Thi PHIP, Hiroshi NOJIMA* and Toru TASHIRO Faculty of Horticulture, Chiba University Abstract •eTouki•f, plants, Angelica acutiloba Kitagawa, are usually cultivated in soil, under which its yield and root quality are unstable. Although fertilizer application exerts a substantial impact on yield, the optimal level has not been known for the cultivation in soil. Therefore, the present study was undertaken to examine the growth of Touki plants with different concentrations of nutrient solution in aeroponic and drip irrigation systems. Four nutrient concentrations, i.e.,100%, 200%, 50%, and 25% of the standard nutrient solution (•gEnshi•hformula) were tested:. In the aeroponic system, where a mist of nutrient solution was sprayed around suspended roots of the plants, the plants were grown from March 15 to June 6, 2005. In the drip irrigation system the plants were grown from May 2 to July 25, 2006. In the aeroponic system, the values of the growth parameters of the Touki plants at 12 weeks after transplanting were higher in the order of 100% > 50% > 200% > 25% of the standard solution. In the drip irrigation system the growth parameters were higher in the order of 100% > 200% > 50% > 25% of the standard solution. The •gEnshi•h nutrient solution of 100% was optimal for the growth of the Touki plants in both systems. The plant growth, especially root growth, was more vigorous in the aeroponic system than in the drip irrigation system. In the drip irrigation system, however, the root/shoot ratio and root C/N ratio were higher, and the development of secondary roots was stimulated. As the secondary roots of Touki plants are mainly used as raw materials for medicine in Viet Nam, the drip irrigation system is recommendable as an advanced culture system. Key Words: Hydroponic culture, Medicinal plants, Mineral nutrition, Touki plant Heavier seeds and seeds having a higher specific Introduction gravity produced more vigorous seedlings. Yomo et al. •e Touki•fplants, Angelica acutiloba Kitagawa, are (1998a) reported that the growth rate of Touki plants in usually cultivated in field soils. The plants often require hydroponic culture was higher than that in conven- 2 years for achieving root maturity in Japan, but one tional soil culture, while the ligustilide content was year in Viet Nam (Pham, 2000). During the growth nearly the same in plants grown both in hydroponic period, the plants are subjected to numerous stresses, culture and soil culture. Yomo et al. (1998b) also such as diseases and insects attacks, which directly reported that Touki plants grown in Kanuma soil affect the productivity and quality. In addition, it is very produced larger roots and exhibited higher values for difficult to determine the optimal quantity of fertilizer the fresh and dry weight than those grown in other for plants grown in soil (Lissner et al., 2003). substrates (e.g. rockwool, river sand, hydroball, etc.). Harvesting of roots, i.e., extracting roots from soil, is Aeroponics is a form of hydroponic system, in extremely laborious and most of the fragile secondary which a mist of nutrient solution is sprayed around roots are lost during the harvest, leading to a roots in a chamber. Aeroponics is effective for substantial loss of potential yield. Low productivity and initiating rooting of cuttings and for extracting low profitability inhibit the expansion of the cultivated ingredients from the roots of medicinal plants area of Touki plants. Therefore, in Viet Nam, 80% of the (Burgess et al., 1998; Pagliarulo et al., 2000; Gontier et total amount of Touki roots is imported from China as al., 2002). Even though aeroponics offers several raw materials for medicinal purposes (National advantages for root crops, such as cleaner roots, soil- Institute of Medicinal Material in Viet Nam, 2000). free materials, compared with soil-based cultivation, In the previous study, Ninh et al. (2006) reported the initial cost for the system and running costs are that selecting seeds based on the weight and specific very high (Soffer, 1985). Accordingly, the aeroponic gravity enhanced the root growth in Touki seedlings. system is often not economically applicable (Jensen Received Oct. 10, 2006 and Collins, 1985). Accepted Mar. 10. 2007 Drip irrigation system is the most popular system * Corresponding author 648 Mastudo, Matsudo city, Chiba 271-8510, Japan used in arid lands, to increase water use efficiency [email protected] (Pruitt et al., 1989; Sezen et al., 2006). Furthermore, Ninh et al.: Effect of nutrient solutions in hydroponic systems on the growth of Touki plant 85 drip irrigation enhances yield because fertilizer is Growth conditions applied directly to active root zones (Hebbar et al., Aeroponic system 2004; Singandhupe et al., 2003). Accordingly, in many Four sets of aeroponic system (Fig. 1A) were instances, drip irrigation creates favorable conditions used, for one treatment each. The aeroponic system in the root zone for root growth. Kanuma soil, a consisted of: (i) an electric timer (H2F-D,OMRON), granular form of volcanic ash soil free of the major (ii) a sub-timer (H3CR-F8N, OMRON), (iii) a pump (C- nutrient elements, as the growth medium is used to P60H, Hitachi), (iv)15 hydro-atomizing spray jets to easily control the desired level of nutrient solution. mist nutrient solution, (v) a tank with 200 L of recycled The main objective of the present study was to nutrient solution, (vi) a micro-clean effluent filtration examine the growth of Touki plants using different system, (vii) drain connectors, and (viii) a chamber concentrations of •gEnshi•h nutrient solution in the (bed). The bed was 3.6 m in length, 0.5m in width and aeroponic system and in Kanuma soil medium in the 0.6m in depth. The vertical walls and the bottom of the drip irrigation system, respectively. bed were covered with a black polythene film to shut light and the top of the bed was covered with 2 cm Materials and methods thick polystyrene foam. The plants were arranged into Plant materials 2 rows in the bed and inserted in holes of 2.5 cm in The experiments were conducted in a greenhouse diameter. Each row contained 18 plants. The plant to located at the Faculty of Horticulture, Chiba University, plant distance in the row was 15cm and the distance Matsudo, Japan. between the two rows was 18 cm. The roots were Touki seedlings (seeds were purchased from hanged in the air and misted with the nutrient solution. Toyama Medicinal Plant Center in Toyama Prefecture, An on-off control system (2 minutes on and 4 minutes Japan) were transferred to pots (6 cm in diameter) off) was installed. To balance the minerals in the filled with the growth media (Tsuchitaro soil) containing nutrient solution, the nutrient solution was exchanged N:P2O5:K2O at rates of 120:1,000: 50 mg/L at pH 6.7. every two weeks during the experiment. Six-month-old seedlings were used for the experi- ments. The aeroponic experiment was carried out from Drip irrigation system March 15 to June 6, 2005 and the drip irrigation Four sets of drip irrigation system (Fig. 1B) were experiment was from May 2 to July 25, 2006. used. The set consisted of : (i) an electric timer (H2F Fertilizer treatments Four treatments with different concentrations of the •gEnshi•h nutrient solution (N:P:K:Ca:Mg) were adopted as follows: (i) standard •gEnshi•h solution (100% standard solution) was composed of 944.6 mg L-1 Ca(NO3)2.4H2O; 808.9 mg L-1 KNO3; 153.4 mg L-1 NH4H2PO4; 492.9 mg L-1 MgSO4, (ii) double concentra- tion of standard solution (200% standard solution), (iii) half a concentration of standard solution (50% standard solution), (iv) a quarter concentration of standard solution (25% standard solution). Electrical conductiv- ity (EC) values of the nutrient solutions were 3.7, 2.5, 1.5 and 0.95 dS/m (i.e. EC of tap water = 0.38 dS/m) for the 200%, 100%, 50% and 25% standard solutions, respectively. The pH was measured with a pH meter Fig,1 Schematic diagrams showing: (A) Sectional view of (Twin pH, Horiba Co., LTD, Japan), and adjusted with the aeroponic system (B) Sectional view of the drip 1N of H2SO4 at 5.5 - 6.0 every day. irrigation system.( In the four treatments, the same micro-nutrient 1) 200 L nutrient solution tank; (2) Pump;(3) Electric concentrations as those of the •gEnshi•h nutrient solution timer; (4) Sub-timer; (5) Electric counter; (6) Digital flowmeter; (7) Foam layer; (8) Plant; (9) Pipe connector were used. and spray jet; (10)Drainage; (11)40 L nutrient solution tank; (12)Pipe connector and emitter 86 Jpn. J. Trop. Agr. 51(3) 2007 D,OMRON), (ii) a sub-timer (H3CR-A, OMRON), (iii) Data analysis an electric counter (H7CX, OMRON), (iv) a pump (C-P60S, Relative growth rate (RGR) and net assimilation Hitachi), (v) a digital flowmeter (DIGMESA FMIG-HO- rate (NAR) was calculated according to equations 1-2 0C4), (vi) 30 emitters with drip tapes to drop the as following: nutrient solution, (vii) a tank with 40 L of nutrient RGR= {ln(W2) - ln(W1) }/(t2 - ti) eqn 1 solution, and 30 potted plants were transplanted in large pots (30 cm height and 16 cm diameter) in a row. NAR = (W2 - W1)•~{ln (LA2) - In (LA1) }/ Kanuma soil (5 mm in diameter; pH, 6.7), was { (LA2 -LA1) X (t2 - ti) } eqn 2 used as substrate to grow Touki plants in the drip irrigation system.