• Korean Journal of Soil Science and Fertilizer
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• v.31 no.3
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• pp.291-300
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• 1998

A study was carried out to evaluate the effect of different salts and their Quantities on the fluctuation and rhizosphere colonization of soil microorganisms. The results obtained are as follows. The electrical conductivities(ECs) of $KNO_3$, $K_2HPO_4$, KCl and $K_2SO_4$ showed negative correlations to the number of gram positive bacteria and gram negative bacteria : the number of bacteria was significantly decreased in the KCl or $KNO_3$ treated group compared to the $K_2HPO_4$ or $K_2SO_4$ treated group. The highest microorganism density of gram negative bacteria, gram positive bacteria and Fusarium sp. in balanced salts-treated soil was observed at $0.5dS\;m^{-1}$, $2.1dS\;m^{-1}$ and $8.0dS\;m^{-1}$ of EC, respectively. The ratio of bacteria to fungi ratio in balanced salts-treated soil substantially decreased as the EC of soil increased. Ten and thirty days after soil treatment with balanced salts, the ratio of bacteria to fungi decreased to 757-1571 and 89-215, respectively. Root colonization density of Fluorescent Pseudomonas in cucumber and tomato significantly decreased as the EC of soil increased, whereas that of Fusarium sp. increased.

• Journal of Bio-Environment Control
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• v.17 no.4
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• pp.252-260
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• 2008

This study was conducted to observe the characteristics of mineral nutrient uptake of single-node cutting rose 'Versilla' and to determine optimal nutrient solution control method for soilless culture of 'Versilla' in a closed hydroponic system. Nutrient solution was managed by five different control methods: macro- and micro-element control in aeroponic system (M&M), macroelement control in aeroponic system (M), nutrient solution supplement in aeroponic system (S); electrical conductivity (EC) control in aeroponic system(EC-A); EC control in deep flow technique system(EC-D). The concentration of $NO_3$-N exceeds optimal range whereas P and Mg decreased at the later stage of plant growth with the EC control method, EC-A and EC-D. The overall mineral nutrient content increased with S. On the other hand the nutrient content at the root environment was maintained optimal with M&M and M. The nutrient solution control methods had significantly effect on the cut-flower quality. In the M&M and M, flower length, fresh weight and root activity were higher than those with the other mineral nutrients control methods. The maximal efficiency of photochemistry (Fv/Fm) was higher for M&M, M and S than that with EC-A and EC-D. Based on the above results, it is highly recommended to control nutrient solution by mineral nutrient control methods (M&M and M) in a closed hydroponic system for single-node cutting rose, 'Versillia'.

• Journal of Bio-Environment Control
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• v.8 no.2
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• pp.115-124
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• 1999

This study was conducted to determine the optimum root zone environment condition and proper nutrient management system for lettuce in hydroponics. For the root zone environment condition, several level of pH and electrical conductivity (EC) were treated respectively. Though all the level of pH 4 to pH 8, except pH 3, performed better growth without any visible physiological disorder, the optimum pH of the nutrient solution for lettuce production was pH 5.5 to 6.0. The optimum ionic strength of the solution was EC 1.2 to 1.6 mS $cm^{-1}$ / because higher nutrient level caused tip burn symptom by calcium deficiency. Considering the above results, it is concluded that lettuce can be efficiently mass-produced through the optimum root zone environment.

• Journal of Bio-Environment Control
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• v.26 no.4
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• pp.418-423
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• 2017

In hydroponics, the nutrient solution is supplied considering the water and nutrient uptake characteristics of crops. However, as the ionic uptake characteristics are changed as a result of the weather conditions or the growth response of the crops, the root zone can not be maintained in optimal condition. In addition, the coir substrate has been used mainly for the tomato cultivation in place of the inorganic substrate, there are few studies on long-term cultivation using coir substrate. Therefore, this study was conducted to investigate the effect of EC level of irrigation solution on tomato growth and inorganic ions of root zone in soilless culture using coir. Coir substrate mixed with 5 : 5 chip and dust was used. EC level of irrigation solution was 1.0, 1.5, 2.0, and $3.0dS{\cdot}m^{-1}$. At the initial stage, $NO_3-N$, P, Ca and Mg in the drainage were lower than the irrigation level at 1.0 and $1.5dS{\cdot}m^{-1}$. However, EC $2.0dS{\cdot}m^{-1}$ or higher, all the ions except P were highly concentrated in the drainage. The average fruit weight was not significantly different between 1.0 and $1.5dS{\cdot}m^{-1}$ until 3th cluster, but from the next cluster, the higher the EC level, the smaller the weight. The number of fruit and yield to 6th cluster was the highest at $1.5dS{\cdot}m^{-1}$. From the next cluster, The yield was decreased with the higher EC level. At the early stage of growth, BER occurred only in EC $3.0dS{\cdot}m^{-1}$, but increased in all treatments with increasing irradiation. The incidence rate of EC $3.0dS{\cdot}m^{-1}$ was higher than that of the lower EC level treatment.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 2002.04a
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• pp.1-2
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• 2002

토마토의 품질을 향상시키기 위한 처리들이 대부분 수량감소를 동반하는데 수량감소를 최소화하면서 품질을 개선할 수 있는 방법을 구명하기 위하여 해수를 처리하여 토마토의 품질을 향상시킬 수 있는 가능성을 검토하였다. 해수에는 Na와 Cl 이온이 80% 이상을 차지하고, EC가 높기 때문에 NaCl을 대체할 수 있을 뿐만 아니라 근권에 EC를 효과적으로 높일 수 있을 것으로 판단되어 수행하였다. (중략)

• Microbiology and Biotechnology Letters
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• v.35 no.1
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• pp.58-65
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• 2007

The role of soil microorganisms, specifically rhizobacteria, in the development of rhizoremediation techniques is important to speed up the process and to increase the rate of mobilization or absorption of heavy metals to the plant. In this study, Methylobacterium sp. SY-NiR1 was isolated from the rhizosphere soils of plants in oil and heavy metal-contaminated soil. Based on its pink pigmented colony, rod-shape cells, and belonging in $\alpha-Proteobacteria$, Methylobacterium sp. SY-NiR1 is considered a pink-pigmented facultative methylotroph. SY-NiR1 had the ability to produce indole acetic acid which is one of phytohormones. This bacterium showed resistance against multiple heavy metals such as Cd, Cr, Cu, Pb, Ni, Zn, and the order of its resistance based on $EC_{50}$ was Zn > Ni > Cu > Pb > Cd > Cr. Therefore, Methylobacterium sp. SY-NiR1 can stimulate seed germination and plant growth in soil contaminated with heavy metals.

• Journal of Bio-Environment Control
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• v.21 no.4
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• pp.348-353
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• 2012

This study was conducted to figure out the possibility of non-drainage in muskmelon (Cucumis melo L.) hydroponics culture. Plants were grown under 3 different levels of drainage, standard (20~40%, SD), minimum (5~10%, MD), and non-drainage (ND). Throughout cultivation periods, constant water content and electrolyte conductivity changes in root zone were observed in SD in the range of 60~70% and $1.5{\sim}2.5dS{\cdot}m^{-1}$, respectively. ND treatment caused the fluctuation in water content and electrolyte conductivity of root zone and its change ranges were 30~50% in water content and $2{\sim}6dS{\cdot}m^{-1}$ in electrolyte conductivity, but ND treatment did not decrease fruit quality. Even if fruit fresh weight was slightly lower in ND with 1,863 g, than in SD with 1,990 g, the fruit weight in ND meets standard market size, 1,800~2,000 g. Higher soluble solids content was observed in fruit in ND than in SD and MD. Total amount of drainage per plant was 27,718, 15,769 and 2,346 mL in SD, MD and ND, respectively. SD showed $83.2m^3$ drainage, 34.5% drainage of irrigation amount whereas required total irrigation amount in ND was very low with $7m^3$.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 1998.05a
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• pp.158-161
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• 1998

고품질 청정채소에 대한 소비자의 선호가 높아지고 있어 신선채소의 규격생산, 주년 대량생산이 가능한 양액재배 방식을 근간으로 한 식물공장이 21세기 새로운 원예작물 생산시스템으로 대두되고 있다. 이들 생산시스템의 최적환경이 구명되어 있지 않은 실정으로 채소의 품질과 비용면에서 효율성 제고의 필요성이 제시되고 있다. (중략)

• Journal of Soil and Groundwater Environment
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• v.16 no.5
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• pp.9-17
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• 2011

Positive effect of multiple-PGPR (Plan Growth Promoting Rhizobacteria), isolated from heavy metal contaminated soil, on the germination of Barnyard grass (Echinochloa crus-galli var. frumentacea) was quantitatively estimated in 5 heavy metal (Cd, As, Ni, Cu, and Pb) contaminated liquid medium. The $EC_{50}$ value for respective heavy metal was estimated by TSK (Trimmed Speraman-Karber) model based on germination rate. The results showed overall increase in $EC_{50}$ with PGPR inoculation. The $EC_{50}$ value increased 1.4% from 96.0 mg/L (control) to 97.4 mg/L (PGPR-treated) in As contaminated medium. In Ni contaminated medium, the $EC_{50}$ value increased 31.9% from 148.0 mg/L (control) to 195.2 mg/L (PGPR-treated), while the $EC_{50}$ showed 4.8% increase from 63.4 mg/L (control) to 66.5 mg/L (PGPR-treated) in Cu medium. Overall seedling growth was stronger in the PGPR treated seeds than that in the control, but positive effect on seedling growth was not conspicuous. At effective concentration of 100 mg/L, the average seedling length of the PGPR treatment in As, Cd, Cu, and Ni medium, respectively, was 1.13, 0.14, 0.40, and 0.06 cm longer than that in the control. However, the increase of seedling growth was statistically insignificant (p < 0.05). These results suggest that inoculation of the isolated-PGPR exerts positive effects on seed germination by reducing heavy metal toxicity and can be an effective tool for application of phytoremediation on heavy metal contaminated soils.

• Korean journal of applied entomology
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• v.51 no.2
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• pp.153-156
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• 2012

Surveys were conducted on the occurrence of nematodes in the root systems of 1-3-year old Cymbidium hybida Swartz cultivated for export in Korea. The most frequently detected plant-parasitic nematode was Ditylenchus sp. with 4.7, 43.7, and 49.7/200 cc growth medium in 1, 2, and 3 year-old cymbidiums, respectively. And the densities of non-parasitic nematodes, dorylaimids, were 35.3, 70.5, and 155.8/200 cc growth medium in 1, 2, and 3-year-old cymbidiums, respectively. Three-year-old cymbidiums collected from Siheung, Ansan, and Gimpo had low densities of Aphelenchus sp. and Aphelenchoides sp. with under 40 individuals/pot, and the dorylaimid densities were 56-824/pot. To evaluate the effects of nematicides on Ditylenchus sp. in cymbidium, Emamectin benzoate EC, Fosthiazate SL, and Cadusafos CS were tested at two farms in Ansan and Gimpo. Emamectin benzoate EC showed control effects of 75.7 and 89.5%, whereas Fosthiazate SL and Cadusafos CS showed 27.2 and 65.3% and 30.1 and 90.5% control effects in the tests.