• Journal of Bio-Environment Control
• /
• v.26 no.4
• /
• pp.424-431
• /
• 2017

This study was conducted to set the optimum nutrient solution concentration by growth stage for new strawberry cultivars 'Berrystar' and 'Jukhyang'(Fragaria ${\times}$ ananassa Duch. cvs. 'Berrystar', 'Jukhyang') grown through hydroponics to improve the quality and yield. Three different EC levels were applied to the nutrient solution. The treatment levels were 0.7, 1.0 and 1.3 times higher than the nutrient concentration standard for 'Seolhyang' based on the 'Manual for strawberry cultivation' of Rural Development Administration. Based on the results, there were no significant differences in growth of 'Berrystar' by EC level. 'Jukhyang' showed the most vigorous growth grown in 1.3 times higher nutrient concentration. While the growth of 'Berrystar' and 'Jukhyang' grown in higher EC level has leaves with more chlorophyll concentration. However the quantum yield of leaves was not affected by the treatments. On the treatment with 1.3 times higher EC level, the weight, length, width and firmness of 'Berrystar' and 'Jukhyang' were significantly high. The sugar contents of the harvest analyzed by HPLC did not differed particularly, but the percentage composition of reducing sugar and non-reducing sugar were presented differently depending on the treatments. Marketable fruit yield increased as nutrient concentration increases. However, there were no large differences by treatments. Meanwhile, 'Jukhyang' showed significant difference by nutrient concentration and had the largest yield for a treatment grown in 1.3 times higher EC level. Based on these results, it is recommended to provide the same nutrient solution concentration level to the nutrient concentration standard of 'Seolhyang' for 'Berrystar', and the 1.3 times higher level for 'Jukhyang'.

• Environmental Analysis Health and Toxicology
• /
• v.25 no.4
• /
• pp.273-278
• /
• 2010

Objectives : This study was aimed to examine the acute toxicity assessment of two new algicides, thiazolidinediones derivatives (TD53 and TD49), which were synthesized to selectively control red tide, to the marine ecosystem. Methods : The assessment employed by a new method using Ulva pertusa Kjellman which has been recently accepted as a standard method of ISO. The toxicity was assessed by calculating the $EC_{50}$ (Effective Concentration of 50%), NOEC (No Observed Effect Concentration) and PNEC (Predicted No Effect Concentration) using acute toxicity data obtained from exposure experiments. $EC_{50}$ value of TD49 and TD53 was examined by 96-hrs exposure together with Solutol as a TD49 dispersing agent and DMSO as a TD53 solvent. Results : $EC_{50}$ value of TD53 was $1.65\;{\mu}M$. From the results, values of NOEC and PNEC were calculated to be $0.63\;{\mu}M$ and 1.65 nM, respectively. DMSO under the range of $0{\sim}10\;{\mu}M$, which is same solvent concentration used in examining TD53, showed no toxic effect. $EC_{50}$ value of TD49 was $0.18\;{\mu}M$ and that of Solutol was $1.70\;{\mu}M$. NOEC and PNEC of TD49 were $0.08\;{\mu}M$ and 0.18 nM, respectively and those for Solutol were $1.25\;{\mu}M$ and 1.25 nM, respectively. Conclusions : From the values of NOEC, PNEC of TD53 and TD49, TD49 showed 9 times stronger toxicity than TD53. On the other hand, DMSO showed no toxicity on the Ulva pertusa Kjellman, but Solutol was found to be a considerable toxicity by itself.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.31 no.4
• /
• pp.461-472
• /
• 2021

Objectives: This study was conducted to determine the differences in EC concentrations according to the type of sampler by measuring and analyzing EC. Methods: Elemental carbon was measured in diesel engine vehicles and at the roadside. Using NIOSH method 5040, a cassette was coupled to 37 mm and 27 mm quartz filters and measurements were performed 21 times. There were 14 types of measurement methods, and polystyrene, polypropylene, and metal samplers were evenly placed inside the movable chamber. Results: The results measured using the 37 mm conductive cassette (closed/open) and the IOM sampler made of conductive materials showed a higher ratio than the other results. When the 37 mm conductive cassette was measured with the lid open, it showed a statistically significantly higher ratio than with other measurement methods (p<0.05). Conclusions: Checking the EC concentration a total of 21 times at each ratio based on the concentration of the 3-stage polystyrene cassette, it was statistically significantly higher when the 37 mm conductive cassette was open. This same cassette also showed a slightly higher EC concentration when closed. It was ascertained that some DEE was collected on the cassette wall surface due to the electrical conductivity of the polystyrene cassette, resulting in sample loss. Since EC is composed of fine particles, it is thought that electrical conductivity may affect its concentration.

• Horticultural Science & Technology
• /
• v.31 no.2
• /
• pp.173-178
• /
• 2013

Experiments were conducted to investigate the optimum concentration of nutrient solution for strawberry 'Maehyang' bred domestically for exportation in hydroponics. Nutrient solutions for strawberry, which was made by Yamazaki, were supplied electrical conductivity (EC) 0.6, 0.8, 1.2, and $1.8dS{\cdot}m^{-1}$ after planting on cocopeat medium during the experiment period. Growth of shoot of strawberries did not show any statistical differences among treatments. Fruit length showed the longest in EC 0.8 and $1.2dS{\cdot}m^{-1}$, followed by 0.6 and $1.8dS{\cdot}m^{-1}$ in the first and third cluster. It showed the shortest in EC $1.8dS{\cdot}m^{-1}$ in the second cluster but there were no significant differences among treatments in the fourth cluster. Fruit diameter did not show significant differences among treatments in the first and second cluster but was the longest in the lowest concentration EC $0.6dS{\cdot}m^{-1}$ in the third cluster. The shortest was in EC $1.8dS{\cdot}m^{-1}$ in the fourth cluster. The heaviest mean fruit weight appeared in EC 0.8 and $1.2dS{\cdot}m^{-1}$, and the lightest was in EC $1.8dS{\cdot}m^{-1}$ in the first cluster and also lightest in EC $1.8dS{\cdot}m^{-1}$ but no significant differences was found among other treatments in the second & third cluster. Also the fruit weight was significantly light in plants grown in EC $1.8dS{\cdot}m^{-1}$ than $0.6dS{\cdot}m^{-1}$ in the fourth cluster. Soluble solids content of fruit was the highest in EC $0.6dS{\cdot}m^{-1}$ in all cluster. As a result, we came to the conclusion that the optimum EC for strawberry 'Maehyang' was EC 0.8 - $1.2dS{\cdot}m^{-1}$ during low temperature season. This result will be utilized as an indicator for strawberry hydroponics.

• Journal of Bio-Environment Control
• /
• v.16 no.2
• /
• pp.108-114
• /
• 2007

This study was conducted to clarify the effects of the different mixing ratios of substrate mixtures based on peat moss and the concentration of nutrient solution on the growth of tomato (Lycopersicon esculentum Mill.) seedlings. Substrates such as peat moss, rice hull, carbonized rice hull, decomposed sawdust, perlite and granular rock wool were mixed and used. The concentration of nutrient solution were adjusted to EC $0.5{\sim}1.5mS/cm$. The volumetric moisture contents became higher as peat moss mixed were much more. Total porosities in all substrate mixtures were over 80%, and pH in substrate mixtures became lower as the volume of peat moss mixed higher. Mixing ratios of substrates suitable for the production of tomato seedlings with the higher quality were peat moss:rice hull:carbonized rice hull:decomposed sawdust:perlite=25:10:25:20:20(v/v). The plant growth was not significant among the different substrate mixtures. However, plant growth such as plant height, leaf area, and total dry weight became significantly increased as EC increasing.

• Korean Journal of Soil Science and Fertilizer
• /
• v.29 no.4
• /
• pp.411-418
• /
• 1996

This experiment was conducted to investigate the effect of electric conductivity (EC) and potassium (K) concentration level in the culture solution on the growth and the air pollution monitoring capability of Perilla frutescens Suwon 16 which was recognized as a possible bioindicator for air pollution. The plants were exposed to $NO_2$, $O_3$, $SO_2$ and $NO_2+SO_2$ within a phytotron at $25^{\circ}C$ (day) or at $20^{\circ}C$(night) with 70% of relative humidity and evaluated the effect of EC and K level on the injury of the plants, The highest dry weights were gained as 16.3 g/plant at 0.5 dS/m of EC and as 32.3 g/plant at 100 and 200mg/l of K concentration, respectively. The diffusive resistances appeared as low values at 0.5 dS/m of EC and at 50, 100mg/l of K concentration. The increasing of the visible injury with increasing the dose of air pollutants could be taken at 0.5. 1.0 ds/m of EC and at 50, 100mg/l of K. The recommendable level of EC and K of the culture solution were 0.5-1.0 dS/m of electric conductivity. 50-100mg/l of K for the plant as an air pollutant biomonitor, when the 7th or 8th leaf was developed.

• The Korean Journal of Pesticide Science
• /
• v.13 no.2
• /
• pp.87-97
• /
• 2009

Octachlorostyrene (OCS) is a persistant and bioaccumulative toxic subtance (PBTs). In this study, acute toxicity tests on algae, daphnia and fish for octachlorostyrene and its isomers were done to determine effective concentration ($EC_{50}$), Lethal concentration ($LC_{50}$), no observed effect concentration (NOEC) or lowest observed effect concentration (LOEC). As a result, NOEC on algae growth inhibition test for octacholorostyrene and 2-, 3-chlorostyrene was determined as $0.50\;mg\;L^{-1}$, and NOEC for 4-chlorostyrene was determined as $0.13\;mg\;L^{-1}$. NOEC on daphnia, acute immobilisation test for octachlorostyrene and 2-, 3-chlorostyrene was determined as $5.00\;mg\;L^{-1}$ and $EC_{50}$ for 4-chlorostyrene was determined as $2.128\;mg\;L^{-1}$. NOEC on Oryzias Latipes, acute toxicity test for octachlorostyrene was determined as $80.0\;mg\;L^{-1}$ and NOEC for 2-, 3-chlorostyrene was determined as $60.0\;mg\;L^{-1}$. $LC_{50}$ for 4-chlorostyrene was determined as $39.0\;mg\;L^{-1}$ (48h) and $22.6\;mg\;L^{-1}$ (96h).

• Korean Journal of Environmental Biology
• /
• v.36 no.4
• /
• pp.517-524
• /
• 2018

The purpose of this study was to investigate the density of thrips, and insecticidal resistance for effective control of Western flower thrips in greenhouse. The presence and density of the thrips was investigated using yellow colored-sticky trap in a cucumber field from May to August in Cheon-an. The results of the investigation revealed the existence of the following thrips species; Frankliniella occidentalis, F. intonsa, Thrips palmi, T. tabaci, Scirtothrips dorsalis, Microcephalothrips abdominalis, and T. nigropilosus. The predominant pest was found to be the western flower thrips. To survey the western flower thrips insecticidal resistance, we established the discriminating concentration (DC), recommended concentration (RC) and $2{\times}$recommended concentration ($2{\times}RC$) of nine insecticides; Emamectin benzoate EC, spinetoram SC, Chlorfenapyr EC, Spinosad SC, Cyantraniliprole EC, Acetamiprid WP, Dinotefuran WG, thiacloprid SC and thiamethoxam SC. The bioassay of about five local populations was conducted using the leaf-dipping method. In all local populations, insecticidal resistance in western flower thrips had not developed in emamectin benzoate EC (RC, $10.8{\mu}L\;L^{-1}$), chlorfenapyr EC (RC, $50.0{\mu}L\;L^{-1}$), spinetoram SC (RC, $25.0mg\;L^{-1}$), and spinosad SC (RC, $50.0mg\;L^{-1}$). However, insecticidal resistance in RC was found to have developed in cyantraniliprole EC (RC, $50.0{\mu}L\;L^{-1}$) and four insecticides of neonicotinoid type. Insecticidal activity of 95% or more was observed in each population when cyantraniliprole EC tested in $2{\times}RC$. However, the neonicotinoid types showed different insecticidal activity in $2{\times}RC$.

• Journal of Bio-Environment Control
• /
• v.12 no.2
• /
• pp.95-100
• /
• 2003

To evaluate the effect of the fertilizer concentration after flowering on growth a31d fruit setting of ornamental pepper (Capsicum annuum L.), plants were fertilized with $100\;mg{\cdot}L^{-1} of N ($EC=0.8\;dS{\cdot}m^{-1}) until flowering, and then with 0 (no fertilizer), 100, 200 or $300\;mg{\cdot}L^{-1} of N (fertilizer solution EC of 0.15, 0.8, 1.45 or $2.10\;dS{\cdot}m^{-1}, respectively) until harvest. Maximum leaf area and shoot dry mass at the end of the growing period were obtained when plants were fertilized with $200\;mg{\cdot}L^{-1} of N. Total fruit number per plant at the end of the growing period was not different when plants were fertilized with 100,200 or 300 mg{\cdot}L^{-1}of N concentration. When plants were fertilized with $200\;mg{\cdot}L^{-1} of N, the number of fruits per plant was decreased significantly as compared to 100, 200 or $300\;mg{\cdot}L^{-1} of N, whereas the percentage of red fruits at the end of the growing period was maximized. Total fruit fresh weight per plant at the end of the growing period was highest with the concentration of $200\;mg{\cdot}L^{-1} of N. The EC of the growing medium remained within 0.8 to $1.2\;dS{\cdot}m^{-1}\;2.0\;to\;3.0dS{\cdot}m^{-1}, or 3.0 to 4.5 dS{\cdot}m^{-1}when fertilizer concentrations were 100, 200 or $300\;mg{\cdot}L^{-1} of N, respectively. Throughout most of the experiment, the pH of the growing medium remained within 5.4 to 6.2, but dropped to 4.9 near the end of the experiment when fertilizer concentration was 200 or 300\;mg{\cdot}L^{-1} of N. Content of most of the nutrients In the leaf was not affected by the different fertilizer concentration. Only aluminum was significantly affected and decreased linearly with increasing fertilizer concentration. The results from this study indicated that optimal fertilizer concentration after flowering for commercial production of ornamental pepper was 100 or $200\;mg{\cdot}L^{-1} of N. At these concentrations, the EC of the growing medium remained approximately within 0.8 to 1.2 and 2 to $3\;dS{\cdot}m^{-1}, respectively. This appears to be the optimal range for vegetative growth or fruit setting of ornamental pepper plants, and indicates that ornamental pepper can be grown with a fairly wide range of fertilizer concentrations.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2000.11a
• /
• pp.40-43
• /
• 2000

Groundwater qualities in Nakdong river region were investigated during 1999 and 2000. Groundwater samples were collected twice from about 150 sites over the region. The EC and TDS obtained in first survey (October, 1999) show rather high values than those in second survey(April, 2000) and this seems to be caused by groundwater temperature. There is obvious positive correlation between EC and TDS. For the study area, the following equation can be written : TDS(mg/l) = <0.64~0.70> x EC($mutextrm{s}$/cm). As the concentration of major ions increases in natural condition, there is a tendency that the ratio of TDS and EC has consistent value. This observation suggests that TDS measurement can be replaced by EC measurement in the some ranges.