• Horticultural Science & Technology
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• v.33 no.6
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• pp.854-859
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• 2015

This experiment was performed to develop a model for nutrition ion concentration and EC in regard to change in pH from 4.0 to 8.0 in nutrient solution. The pH changes according to the variation of $HPO_4{^{-2}}$ and $H_2PO_4{^-}$ in the nutrient solution while variation of EC increased from pH 4.0 to 5.0, stabilized from pH 5.0 to 7.0 and increased again from pH 7.0 to 8.0. For the variance of major elements in the nutrient solution, K, Ca, N and P increased while pH was higher, especially the variables for K and P were increased largely. On the other hand, variables of Mg and S were stable. Based on analysis of the ion balance model of nutrient solution, the cation increased than anion over rising the variation of pH while balance point of ion moved from a-side to d-side. In addition, the imbalance increased while it moved away from the EC centerline as variance of pH increased. It was larger than effect of EC variance to correction values of equivalence ratios of K and Ca about variation of $HPO_4{^{-2}}$ and $H_2PO_4{^-}$ while as variance of pH increased, K decreased but Ca increased. These showed the result that variance of pH about correction values of equivalence ratios of K and Ca gave a second-degree polynomial model rating of 0.97. Through this research, it was identified the pH variable model about variance among pH, ion and EC according to gradient of phosphate.

• Research in Plant Disease
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• v.24 no.1
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• pp.26-32
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• 2018

Fusarium wilt on strawberry plants caused by Fusarium oxysporum f. sp. fragariae (Fof) is a major disease in Korea. The prevalence of this disease is increasing, especially in hydroponic cultivation in strawberry field. This study assessed the effect of nutrition solution pH and electrical conductivity (EC) on Fusarium wilt in vitro and in field trials. pH levels of 5.0, 5.5, 6.0, 6.5, 7.0, and 7.5 were assayed in vitro and in field trials. EC levels at 0, 0.5, 0.8, 1.0, and $1.5dS{\cdot}m^{-1}$ were assayed in field trials. Mycelial growth of Fof increased with increasing pH and was highest at $25^{\circ}C$ pH 7 and lowest at $20^{\circ}C$, pH 5.0 in vitro. The incidence of Fusarium wilt was lowest in the pH 6.5 treatment and highest in the pH 5 treatment in field trials. At higher pH levels, the EC decreased in the drain solution and the potassium content of strawberry leaves increased. In the EC assay, the severity of Fusarium wilt and nitrogen content of leaves increased as the EC increased. These results indicate that Fusarium wilt is related to pH and EC in hydroponic culture of strawberry plants.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.1
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• pp.77-85
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• 1995

To develop a simple test for evaluation crop tolerance to acid rain disks of recently matured leaves of 12 crops（rice, corn, barley, wheat, soybean, adzuki bean, Chinese cabbage, radish, lettuce, spinach, and tomato） were soaked in simulated acid rain（SAR） solutions for 1, 2, 3, and 4 hours. Changes in pH and electrical conductivity（EC） of leaf soaked solutions and changes in the color of the soaked leaves were observed. The pH and EC of leaf soaked solutions differed depending on the pH of SAR, crops, and soaking time. Among the crops differences in pH of leaf soaked solutions were most stable and significant for 1∼4 hour soaking in pH 4.0 SAR solution, but those of EC were for 1∼4 hour solaking in pH 5.0 SAR soultions. Color of leaves soaked in pH 2.0 SAR solutions was changed significantly, but not in the pH 3.0 or higher SAR solutions. Vis-ual damages of intact leaves caused by spray of pH 2.0 SAR solution in the greenhouse was posi-tively correlated with pH changes in pH 4.0 SAR solution, but not with EC changes in pH 5.0 SAR solution or color changes of leaves soaked in pH 2.0 soulution. The pH of solution was posi-tively correlated with Ca and Mg concentrations of the solutions and EC was positively correlated with K, Ca, and Mg.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.6
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• pp.555-562
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• 2010

For the rapid and reliable detection of toxic compounds in water, a novel toxicity detection methodology based on sulfur-oxidizing bacteria (SOB) has been developed. The methodology exploits the ability of SOB to oxidize elemental sulfur to sulfuric acid in the presence of oxygen. The reaction results in an increase in electrical conductivity (EC) and a decrease in pH. Using a synthetic stream water (EC=0.12 mS/cm and pH=7.2), the baseline steady-state EC and pH values were 0.5~1.2 mS/cm and ~2.5 over 7 days of testing at HRT 30 minutes. When nitrite compounds were added to the system, the effluent EC decreased and the pH increased due to the inhibition of the SOB. Optimum HRT was 30 min and this HRT could be decresed by using smaller sulfur particles.

• Journal of Bio-Environment Control
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• v.4 no.2
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• pp.203-210
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• 1995

Using the programmable logic controller (PLC), a kind of microcomputer, a facility to control EC and pH automatically in nutriculture of tomato was developed. A program for the automatic control of nutriculture was written in ladder diagram language. EC and pH levels of nutrition solution could be maintained at 1.70-1.72 and 6.1-6.5, respectively, during the entire growing period. Better fruits and higher yield were obtained in automatic control plot than in the control plot. Inorganic elements in plant were higher in the former than in the latter.

• Korean Journal of Soil Science and Fertilizer
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• v.38 no.5
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• pp.247-252
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• 2005

Soil pH is an intensity factor of releasing hydrogen ion which is buffered by aluminum. It depends on pH buffer capacity of Al whether soil pH is governed directly by cations or not. A study was conducted to elucidate the pattern of pH changes by soil EC. Fertilizer and three kinds of organic manures composed of cow and pig and fowl dropping and one kind of rice straw compost were added independently into upland sandy loam soil. This treated soils and four upland soils under plastic film house having different levels in electrical conductivity (EC) were incubated with field capacity at $30^{\circ}C$ for 5, 10, 20 and 40 days. Soil pH varied directly as the cations contained in organic materials according to degree of saturating pH buffer capacity (pBC) of sandy loam soil. pH of the soils under plastic film house was lowered by soil EC due to governing by overplus of cation beyond pBC.

• Horticultural Science & Technology
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• v.16 no.3
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• pp.352-354
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• 1998

A soilless culture system with the precise control of nutrient solution was developed and the time changes of ionic contribution to EC reading was analyzed. The measuring device designed was able to wash electrodes cleanly and to measure the pH and EC of nutrient solution stably in the box. The nutrient supply system using metering device was also able to control the EC and pH within ${\pm}0.05mS/cm$ and ${\pm}0.05$, respectively. Under the EC control, activity coefficients of all ions decreased with time as ionic concentrations of $SO_4$, Mg and Ca increased due to the selective nutrient absorption by plants. Time changes of ionic contribution to EC reading could be calculated using equivalent ionic conductivities and activity coefficients obtained by numerical analysis.

• Journal of Korean Society of Forest Science
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• v.86 no.1
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• pp.56-68
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• 1997

This study was carried out to evaluate the capacity of environment purification of forest and to reveal formation processes of stream water quality by evaluating water quality variations in forest hydrological processes. Water quantity, pH, electric conductivity(EC), dissolved oxygen(DO), and dissolved matter concentrations were monitored in open rainfall, throughfall, stemflow, litter flow and short-term stream flow for one unit storm, and also for those were monitored in long-term stream flow in Palgong, Yongsung, and Daedong catchments. The results were summarized as follows; 1. pH and DO values of stream flow were increased as the flux increased but EC values were decreased. 2. pH values of stemflow and throughfall were decreased with the lapse of rainfall time with lower values than open rainfall. Arid EC values were higher in initial rainfall period but lower gradually with the lapse of time than open rainfall. In litter flow, pH values were lower than open rainfall but EC values were higher. In stream flow, pH values of stream flow showed a high level in initial rainfall period and decreased remarkably with the lapse of time, but it recovered after the rainfall stopped. And however, the values of EC showed almost reverse tendency. DO values of litter flow and stream flow were decreased gradually with the lapse of time in litter flow and stream flow but there were no any tendency in open rainfall, stemflow and throughfall. 3. pH values of stemflow and throughfall in Quercus acutissima were higher than in Pinus densiflora, but EC values were lower. Total amount of canons in stemflow was higher in Pinus densiflora than in Quercus acutissima. 4. pH, DO, EC and total amount of cation values in hydrological processes were in the order of; litter flow

• Journal of the Korean Society of Groundwater Environment
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• v.7 no.3
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• pp.125-132
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• 2000

pH, EC and TDS are basic components in the investigation of groundwater quality, and are very important to the preliminary assessment of groundwater quality. These three chemical components investigated at the Youngsan and Sumjin river basins in 1998 suggest that the groundwater quality is generally good in these basins. Linear regression analysis shows that TDS versus EC has an linear correlation, but EC versus pH, and TDS versus pH have nearly no correlation. The relation of TDS and EC is 1.0 mg/1=1.52 $mu\textrm{S}$/cm, and it is the quality of natural water. In geostatistical analysis. three kinds of data are stationary random functions and they have exponential variograms. According to the isopleth maps of the groundwater quality, the groundwater quality of the Youngsan river basin is more contaminated than that of the Sumjin river basin. The isopleth maps of TDS and EC show very similar patterns because of the strong correlation between TDS and EC. The minimum and maximum values of the groundwater quality data are not reflected on the isopleth maps because kriging produces smooth distributions with minimum estimation variances.

• Journal of Korean Society of Forest Science
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• v.90 no.4
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• pp.413-419
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• 2001

This study investigated pH values and EC changes of rainfall and stemflow were investigated for 5 tree species such as Pinus koraiensis, P. densiflora, Larix leptolepis, Quercus variabilis and Q. mongolica in the Experiment Forests, College of Forest Science, Kangwon National University. The results were as follows; 1. Mean month pH values of stemflow were much lower than those of rainfall. Among tree species, pH values of the coniferous such as P. densiflora, P. koraiensis and L. leptolepis were lower those of the deciduous such as Q. mongolica and Q. variabilis. Mean month pH values of stemflow ranged from 3.23 to 5.03 (average : 4.23) for P. koraiensis, 3.57 to 5.16 (average : 4.36) for P. densiflora, 3.41 to 6.69 (average : 4.45) for L. leptolepis, 3.86 to 6.11 (average : 4.70) for Q. variabilis and 4.39 to 6.13 (average : 5.18) for Q. mongolica. 2. Mean month EC of the coniferous species was 1.5 to 2 times higher than that of the deciduous species. Mean month EC of stemflow for P. koraiensis, P. densiflora, L. leptolepis, Q. variabilis and Q. mongolica was ranged from 29.0 to $946.5{\mu}S/cm$(average : $258.5{\mu}S/cm$), 18.6 to $907.5{\mu}S/cm$(average : $220.3{\mu}S/cm$), 27.0 to $918.0{\mu}S/cm$(average : $216.2{\mu}S/cm$), 16.5 to $301.6{\mu}S/cm$(average : $125.4{\mu}S/cm$) and $25.2{\sim}225.7{\mu}S/cm$(average : $101.5{\mu}S/cm$), respectively. 3. Average pH values and EC were highly variable according to season. Average pH values appeared lower in spring than those in summer and autumn, but EC appeared higher in spring than those lower in summer and autumn. 4. According to precipitation, there was little difference in and pH values of stemflow the coniferous and the deciduous showed low pH valuess in the case of less than 50mm precipitation. However, EC of stemflow showed a difference depending on the precipitation, and EC of the coniferous and the deciduous was high more than $100{\mu}S/cm$ at the precipitation of less than 50mm.