• Journal of Bio-Environment Control
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• v.11 no.4
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• pp.168-174
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• 2002

A new circulating hydroponic system was invented for oriental melons grown in the greenhouse. For developing nutrient solution management techniques, we examined the changes of nutrient contents of circulating solution in three different types of new hydroponic systems. The yield and fruit quality of oriental melons in Hydroponics were better than those in soil culture. The substrate culture was appropriate fer hydroponics of oriental melons, and NFT was turned to be the opposite due to the physiological disorder during hot seasons. Yamazaki's melon solution with EC 2.0dS.m$^{[-10]}$ was the most appropriate for oriental melons. The new circulating hydroponic system seemed to be appropriate for oriental melons because of the stable EC, pH and the macro- and micro-element contents. NO$_3$-N, Ca and Mg contents in the circulating solution kept a good balance in all types of hydroponics. However, p content, compared to other types, decreased by the degree of 1 me.L$^{[-10]}$ in perlite medium. K content showed irregular status in perlite but showed the stable status in cocopeat. Generally, microelements, except Mo, showed stable absorption in the substrate culture. However, in NET, most of the elements showed irregular absorption except B and Mn. Microelement absorption, especially Cu, Zn and Mo, decreased during hot seasons.

• Journal of Bio-Environment Control
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• v.7 no.1
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• pp.71-77
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• 1998

The root-zone environment is an important factor to the plant growth and it is closely related to the thermal characteristics of the root media. In this study thermal characteristics of root media with ambient environmental conditions were analyzed. The temperatures of nutrient solution as well as inside air of culture bed were measured in Nutrient Film Technique(NFT) and Deep Flow Technique(DFT) systems, and also the temperatures of root media measured in aggregate culture systems , The temperature of nutrient solution of NFT system with as low as 3$\ell$/min of flow rate was 3$^{\circ}C$ higher than that with 5 $\ell$/min of flow rate in the daytime, and the temperature of inside air was 2$^{\circ}C$ higher at night. And the temperature of nutrient solution of DFT system with as low as 0.8 cm of water level was 1-2$^{\circ}C$ higher than that with 1 8 cm in the daytime, and the temperature of inside air was almost same at night. The root-zone temperatures in the perlite and rockwool granulate systems with film mulching were 3$^{\circ}C$ higher than those without film mulching in the daytime. However, the rockwool slab system with film mulching showed the same trend as rockwool granulate system, but relatively higher temperature than any other medium because of the exposure of media surface to the ambient air. Additionally the temperature below the plant was measured 3$^{\circ}C$ lower than that between plants.

• Journal of Bio-Environment Control
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• v.13 no.4
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• pp.240-244
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• 2004

This study was conducted to evaluate the effect of different surfactants on the fertilizer reduction and increase of the mineral nutrients uptake of lettuce (Latuca sativa L. 'Hanbatchungchima') in deep flow technique culture. The measured items from lettuce leaves expanded fully were growth, photosynthetic and transpiration rate, and mineral nutrient content K, Ca and Mg, respectively. The highest growth were observed at $0.3mg{\cdot}L^{-1}$ polyvinyl alcohol (PV4-95) treatment, including lettuce grown in the half strength of nutrient solution. The highest photosynthetic rate, transpiration rate and mineral nutrient content were observed at $0.3mg{\cdot}L^{-1}$ calcium lignosulfate (CLS) treatment. Therefore, high-quality leaf lettuce production could be achieved by apply proper surfactants PVA-95 and CLS, which can cut down the total amount of fertilizer and increase uptake of mineral nutrients.

• Korean Journal of Environmental Agriculture
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• v.14 no.2
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• pp.246-249
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• 1995

This study was conducted to establish the optimal ratio of $NO_3^-$ and $NH_4^+$ for the nutrient culture of Gerbera hybrida Hort. The results were summarized as follows; 1. The growth of 'Volga' was best in 8 : 2($NO_3^-$ : $NH_4^+$) solution, while that of 'Mirage' was in 9 : 1 ratio. 2. The maximum quantity of cut flowers could be harvested in the 8 : 2 solution in 'Volga', whereas in 9: 1 solution in 'Mirage', but the differences between 9 : 1 and 8 : 2 were not significantly great. 3. In 'Volga', the qualities of cut flowers were not different among 10 : 0, 9 : 1 and 8 : 2, while those in 'Mirage' were not different among all treatments. 4. It turned out that the optimum ratio of $NO_3^-$ and $NH_4^+$ for the nutrient culture of gerbera in the farm house was 8 : 2, irrespective of cultivas.

• Korean Journal of Environmental Agriculture
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• v.20 no.1
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• pp.28-33
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• 2001

Lettuces were grown hydroponically in three different nutrient solutions, normal and 30 or 50 mM $KNO_3-added$ nutrient solutions, and the electrical conductivities of the nutrient solutions were 1.0, 4.5, and 6.5 dS/m, respectively. Lettuces grown in the $KNO_3-added$ nutrient solutions showed a decrease in the germination ratio and the lower indices of growth, such as plant height, stem diameter, leaf length, and leaf width. Microsomes were prepared from the roots of lettuce and characteristics of microsomal ATPases were investigated. The activities of microsomal ATPases grown in the 30 mM and 50 mM $KNO_3-added$ nutrient solutions were higher than that grown in the normal nutrient solution. The highest activities of microsomal ATPases were observed at pH 7.0 in all culture conditions. The activities of microsomal ATPases were increased in a reaction buffer solution containing high concentration of $K^+$, whereas they were decreased in a reaction buffer containing $Na^+$. The stimulating effect of $K^+$ in the reaction buffer was greater on the microsomal ATPases of lettuces grown in the $KNO_3-added$ nutrient solutions than that grown in the normal nutrient solution. These results imply that the activities of microsomal ATPases in the root tissue are increased as increasing the $KNO_3$ concentration in the hydroponical nutrient solution.

• Journal of Animal Environmental Science
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• v.15 no.1
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• pp.51-58
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• 2009

The compost leachate was dark-colored solution that leaches out of the bottom of the compost pile. The compost leachate was rich in nutrients and can potentially used in plant culture. In the organic production, commercial liquid fertilizer was used to insure the availability of nutrients during the formation of the yield. The cost of supplemental liquid fertilizer could be reduced by developing a fertilizer based on animal fertilizer. This experiment was conducted to investigate the effect of different combination of compost leachate and conventional inorganic solution in hydroponic culture for lettuce growth. Six different treatments were applied. The compost leachate(CL) and nutrient solution(NS) were mixed by six different mixing ratios of 0:100, 20:80, 40:60, 60:40%, 80:20 and 100%:0% based on nitrogen content. The chemical nutrient solution was the solution of National Horticulture Research Station for the growth of leaf lettuce. The concentration of nutrient solution was adjusted 1.5 mS/cm in EC. The compost leachate was low in phosphorus(P), calcium(Ca), magnesium(Mg), but rich in potassium(K). The plant height of lettuce treated with CL 20+NS 80% was similar with 100% NS of control plot. Plant height was highest in the plot of CL 20+NS 80%. The treatment of 100% compost leachate was lowest in the growth characteristics of leaf lettuce. Number of leaf was very low in 100% compost leachate compared with plot of chemical nutrient solution. In the beginning of growth stage, SPAD value was reduced in plot treated with CL100%, but CL20+NS80% plot was higher compared to 100% compost leachate. SPAD value of leaf lettuce leaves was decreased as the amount of CL was increased. The dry weight of lettuce were 107.4, 104.2g in plot of NS 100% and CL 20%+NS80%, respectively. The leaf number and plant weight were decreased at high application plots of compost leachate. The leaf lettuce showed lowest in the plot treated with 100% compost leachate, and the growth of lettuce severely decreased after application of 100% CL treatment. The results showed that compost leachate can be use as liquid fertilizer for the organic hydroponic production. The mixture solution of 20% of compost leachate and 80% of nutrient solution could be used as a nutrition solution in hydroponic culture of leaf lettuce. Our studies have shown that is possible to produce using compost leachate, although growth is slower than when using a conventional inorganic hydroponic solution.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 2004.11a
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• pp.39-42
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• 2004

• Journal of Bio-Environment Control
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• v.4 no.2
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• pp.181-187
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• 1995

This study was conducted to investigate the effect of NH$_4$H$_2$PO$_4$ on pH of the nutrient solution using municipal tap water during hydroponic culture of crisp lettuce (Lactuca sativa var. capitata) seedlings. The composition of starter solution was different from that of supplementary solution. The pH in the nutrient solution was suddenly declined and recovered as the supplementary solution was supplied. The pH of nutrient solution was increased with high temperature and, on the contrary, the EC of nutrient solution was decreased. It shows that plant absorbed nutrients more than water in given solution when the temperature and light was high. After supplying supplementary solution in 1st and End experiment, pH was slowly increased to 7 in NH$_4$H$_2$PO$_4$ 0.25me/$\ell$, but maintained 6.4-6.5 in NH$_4$H$_2$PO$_4$ 3me/$\ell$ and 6me/$\ell$. In 3rd experiment, pH was slowly increased from 6.7 to 7.4 in NH$_4$H$_2$PO$_4$ 0.25me/$\ell$, but decreased from 6-6.5 to 5-5.5 in NH$_4$H$_2$PO$_4$ 3me/$\ell$ and 6me/$\ell$. So it is suggested that the concentration between 0.25 me/$\ell$ and 3 me/$\ell$ by concentration base or the amount of NH$_4$H$_2$PO$_4$ between 1me/6 $\ell$ and 7me/6 $\ell$ by total quantity in solution is appropriate for stabilizing pH in the nutrient solution. Also this experiment suggests that hand operated measurements must be cautious due to the change of pH and EC within a 24-hour cycle.

• Journal of Bio-Environment Control
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• v.14 no.3
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• pp.203-211
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• 2005

The experiment was conducted to investigate the nutrition absorption pattern in the growth stages and develope the optimal nutrient solution hydroponically grown the tomato in closed substrate culture system with the nutrient solution of National Horticultural Research Station in Japan into 1/2S, 1 S, and 2S. When plant was grown in 1/2 S, the growth and yield were high and the pH and EC in the rooting zone were stable. Suitable composition of nutrient solution for tomato was $NO_3-N$ 7.1, $PO_{4}$-P 2.1, K 4.0, Ca 3.1, Mg 1.2, and $SO_{4}-S\;1.2\;me{\cdot}L^{-1}$ in the early growth stage and $NO_3-N$ 6.5, $PO_4-P$ 2.3, K 3.4, Ca 3.1, Mg 1.1, and $SO_4-S\;1.1\;me{\cdot}L^{-1}$ in the late growth stage by calculating a rate of nutrient and water uptake. To estimate the suitability for the nutrient solution of tomato in a development of optimum nutrient solution of tomato developed by Wonkwang university in korea (WU), plant was grown in perlite substrate supplied with different solution and strengths(S) by research station for greenhouse vegetable and floricultuin in the Netherlands (Proefstation voor tuinbouw onder glas te Naaldwijk; PTG) of 1/2 S, 1 S and 2 S, respectively, The growth was good at the PTG and WU of 2 S in early growth stage, and at the WU 2S in late growth stage. The highest yield of tomato obtained in the WU of 2 S, although blossom-end rot was appeared in all treatments. pH and EC in root zone of WU of 2 S were stable during the early and late growth stage. Therefore when plant was grown in WU of 2 S, N and P content in the nutrient solution need to low, according N and P content of their leaves were high in WU of 2 S.

• Horticultural Science & Technology
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• v.29 no.1
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• pp.29-35
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• 2011

Individual ion concentrations and ionic contributions to EC reading in the circulated nutrient solution are the important factors to be considered for stable EC-based closed-loop soilless culture. This study was conducted to determine appropriate ion-analysis intervals of the circulated nutrient solutions based on ion concentration, ion balance, and ion electrical conductivity under different renewal intervals in EC-based nutrient control systems for sweet peppers (Capsicum annum L. 'Fiesta') in early growth stage. Average node numbers of the plants were 13 and 18 when the experiment started and finished, respectively, and three plants were grown in each rockwool slab. Four different renewal intervals of circulated nutrient solutions such as 1, 2, 3, and 4 weeks were used as treatment. Nutrient solutions were supplied to the plants based on integrated radiation. Drainage was collected into drain tanks after irrigation ended in the day and then mixed with fresh water until the EC reaches 2.69 $dS{\cdot}m^{-1}$. The replenished nutrient solution was supplied to the plants in the next day. Ion concentrations of the individual ions periodically analyzed in the circulated nutrient solutions showed no significant differences among the treatments during the experimental period. Ion concentrations of $K^+$, $Ca^{2+}$, $Mg^{2+}$, $Na^+$, $NO_3{^-}$, ${SO_4}^{2-}$, ${PO_4}^{3-}$, and $Cl^-$ varied within 5-8, 11-14, 2.0-2.7, 0.5-0.6, 14-19, 4-5, 1-4, and 0.3-0.5 $meq{\cdot}L^{-1}$, respectively. Ion balance showed a consistent tendency over all the treatments and especially $K^+$ : $Ca^{2+}$ and ${SO_4}^{2-}$ : ${PO_4}^{3-}$ played great roles in the cation and anion balances in the nutrient solutions, respectively. Activity coefficients of ions such as $K^+$, $NO_3{^-}$, and $H_2PO_4{^-}$ varied within 0.8-0.9 and those of $Ca^{2+}$, $Mg^{2+}$, ${SO_4}^{2-}$ varied within 0.5-0.6, showing little changes with time. Ionic contributions of $K^+$ and $NO_3{^-}$ to EC reading were the greatest followed by $Ca^{2+}$, ${SO_4}^{2-}$, and $Mg^{2+}$ in the order. From the results, we thought that allowable ranges in ion concentration, ion balance, and subsequent individual ionic contributions to EC reading would be obtained within 4-week renewal interval of nutrient solution in EC-based closed-loop soilless culture for sweet pepper plants.