• Horticultural Science & Technology
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• v.33 no.6
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• pp.845-853
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• 2015

The objective of this study was to predict the timing of nitrogen (N) demand through analyzing chlorophyll fluorescence (ChlF), soil-plant analysis development (SPAD), and normalized difference vegetation index (NDVI), which are positively correlated with foliar N concentration in star cluster (Pentas lanceolata). The plants were grown in potting soil under optimal conditions for 30 d, followed by weekly irrigation with five concentrations (0, 4, 8, 16, and 24 mM) of N for an additional 30 d. These five N application levels corresponded to leaf N concentrations of 2.62, 3.48, 4.00, 4.23, and 4.69%, respectively. We measured 13 morphological and physiological parameters, as well as the responses of these parameters to various N-fertilizer treatments. The general increases in Dickson's quality index (DQI), above-ground dry weight (DW), total DW, flowering rate, ${\Delta}F/Fm$', and qP in response to treatment with 0 to 8 mM N were similar to those of SPAD, NDVI, and Fv/Fm. Consistent and strong correlations ($R^2$= 0.60 to 0.85) were observed between leaf N concentration (%) and SPAD, NDVI, ${\Delta}F/Fm$', and above-ground DW. Validation of leaf S PAD, NDVI, and ${\Delta}F/Fm$' revealed that these vegetation indices are accurate predictors of leaf N concentration that can be used for non-destructive estimation of the proper timing for N-solution irrigation of P. lanceolata. Moreover, irrigation with 8 mM N-fertilizer i s recommended w hen leaf N concentration, SPAD, NVDI, and ${\Delta}F/Fm$' ratios are reduced from their saturation values of 4.00, 50.68, 0.64, and 0.137%, respectively.

• Korean Journal of Soil Science and Fertilizer
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• v.30 no.4
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• pp.314-327
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• 1997

A 2-dimensional soil water flow model was developed to describe the migration of soil moisture in drip-irrigated root zone employing cylindrical coordinate system. Several natural phenomena were incorporated into the model such as transpiration, various types of evaporation, and ponding due to the increase in irrigation rate. Model was solved numerically by finite difference method. The model was verified in several ways leading to the conclusion that it can describe the soil moisture migration in drip-irrigated root zone fairly well. From sensitivity analysis, vertical migration of soil moisture was found to move faster than the horizontal one, which indicates the vertical location just under the dripping point are adequate for measuring points of soil moisture. The pot shape of soil moisture in irrigated zone was proved to be caused by evaporation at the soil surface. Also, it was found that the hydraulic conductivity has greatly influential to the soil moisture migration, and that the soil moisture continues to migrate vertically after irrigation stops.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.45 no.1
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• pp.26-31
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• 2000

This study was carried out to obtain the basic information for breeding cold-tolerant rice varieties with high yield-productivity through wide crosses between indica and japonica rice. Genetic analysis was conducted using 55 F$_1$s obtained from half-diallel crosses among eleven cultivars of various origin including indica and japonica rice. Screening for cold tolerance was done with cold-water irrigation after transplanting until ripening stage. Both general combining ability (GCA) and specific combining ability (SCA) effects were highly significant in all characters associated with dry matter accumulation at 30 and 50days after cold-water irrigation (DAC). The variance of GCA was much larger than that of SCA in plant height, shoot dry weight per plant (DWP), crop growth rate (CGR) and cold-water response index (CRI) of these characters except CRI of shoot dry weight per plant. The DWP, CGR and CRI of these characters of Gaochan 102, Tong88-7 and TR22183 were markedly higher than those of the others. GCA effects of these varieties on DWP, CGR and their CRI were also higher than those of the others, indicating that they are useful as promising parents for breeding cold-tolerant varieties. Analysis of genetic parameters for 11$\times$11 half-diallel F$_1$s revealed that inter-locus gene interaction were concerned in the expression of plant height at 50 DAC, CRI of DWP at 50 DAC, and CRI of CGR, and that intra-locus gene interaction for plant height and the other characters were partial dominance and over-dominance, respectively. Narrow-sense heritability (h$^2$$_{N}$) was the highest in plant height as 0.729, and the lowest in CRI of DWP at 30 DAC as 0.048, suggesting that selection for cold tolerance will be quite effective in case that the selection criterion is the performance itself.f.

• Journal of Radiation Protection and Research
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• v.29 no.2
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• pp.117-127
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• 2004

A dynamic compartment model was developed to evaluate the transport of accidently released radionuclides onto rice-fields. In the model, the surface water compartment and shoot-base absorption were introduced to account for the effect of irrigation, which is essential to a rice cultivation. The soil mixing by plough and irrigation before transplanting rice was also considered, and the rate of root-uptake and shoot-base absorption were modeled in terms of the function of biomass. In order to test the validation of the model, it was applied to the analysis of some simulated $^{137}Cs$ deposition experiments that were performed while cultivating rice in a greenhouse using soils sampled from rice-fields around Kori, Yonggwang and Ulchin nuclear power plants. The model prediction was generally agreed within about one order of magnitude with experimental data.

• Korean Journal of Ecology and Environment
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• v.47 no.spc
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• pp.19-30
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• 2014

Microcystins (MCs) produced by cyanobacteria are severe hepatotoxins for mammalian and protein phosphatase inhibitors. Irrigation water for grain and vegetables is often contaminated with cyanobacteria and microcystin during warm seasons. We assessed the effects of various concentrations (0, 0.01 to $10{\mu}gmL^{-1}$) of microcystin-LR (MC-LR) and microcystin-RR (MC-RR) exposure on Oryza sativa (rice) and Brassica oleraces var. italica (broccoli). The $EC_{50}$ of leaves and roots of rice was 0.9 and $1.1{\mu}gMC-LRmL^{-1}$, respectively. The no observed effect level (NOEL) of rice was less than $0.1{\mu}gmL^{-1}$ ($100{\mu}gL^{-1}$). The $EC_{50}$ of the stems and roots of broccoli was 8.7 and $7.2{\mu}gMC-RRmL^{-1}$, respectively. There was no difference in the germination rate of broccoli among microcystin-RR concentrations. After exposure to 0, 0.01 to $10{\mu}gmL^{-1}$ MC-RR for seven days, 14, 89 and 154 ng mg-1 (dry weight) MC-RR accumulated in B. oleracea. These $EC_{50}$ values showed that microcystin-LR and -RR affected the growth of rice and broccoli. These findings suggest that MC is carried into terrestrial ecosystems via irrigation, and that the biota of higher ecological niches can be influenced by MC through bioaccumulation. Therefore, a guideline for MC concentrations in irrigation water should be set using the NOEL.

• Proceedings of the Korean Society of Crop Science Conference
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• 2005.04a
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• pp.98-99
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• 2005

• KCID journal
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• v.4 no.2
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• pp.25-37
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• 1997

Flow rate and selected water quality of 2 small rural streams located in Kangwon-do, Korea, were monitored and land use of the watersheds was investigated to describe the trend of stream water quality for 2 years. Water qualities were analyzed with respec

• Journal of Bio-Environment Control
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• v.18 no.4
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• pp.309-315
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• 2009

Maintenance of adequate soil water content during the period of crop growth is necessary to support optimum plant growth and yields. A better understanding of soil water movement for precision irrigation would allow efficient supply of water to crops, thereby resulting in minimization of water drainage and contamination of ground water. This research reports on the characterization of spatial and temporal variations in water contents through three different textured soils, such as loam, sandy loam, and loamy sand, when water is applied on the soil surface using an one-line drip irrigation system and the soils are dried after the irrigation stops, respectively. Water contents through each soil profile were continuously monitored using three Sentek probes, each consisting of three capacitance sensors at 10, 20, and 30cm depths. Spatial variability in water content for each soil type was strongly influenced by soil textural class. There were big differences in wetting pattern and the rate of downward movement between loam and sandy loam soils, showing that the loam soil had a wider wetting pattern and a slower rate of downward movement than did the sandy loam soil. The wetting pattern in loamy sand soil was not apparent due to a low variability in water content (< 10%) by a lower-water holding capacity as compared to those measured in the loam and sandy loam soils, implying that the rate of water drainage below a depth of 30cm was high. When soils were dried, there were highly exponential relationships between water content and time elapsed after irrigation stops ($r^2$${\geq}$0.98). It was estimated that equilibrium moisture contents for loam, sandy loam, and loamy sand soils would be 17.6%, 6.2%, and 4.2%, respectively.

• Journal of Wetlands Research
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• v.23 no.4
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• pp.287-295
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• 2021

As facilities such as dam reservoir wetlands and agricultural irrigation reservoir wetlands are built, sedimentation occurs over time through erosion, sedimentation transport, and sediment deposition. Sedimentation issues are very important for the maintenance of reservoir wetlands because long-term sedimentation of sediments affects flood and drought control functions. However, research on resignation has been estimated mainly by empirical formulas due to the lack of available data. The purpose of this study was to calculate and compare the sediment deposition rate by developing a multiple regression model along with actual data and empirical formulas. In addition, it was attempted to identify potential causes of collapse by applying it to 64 reservoir wetlands that suffered flood damage due to the long rainy season in 2020 due to reservoir wetland sedimentation and aging. For the target reservoir, 10 locations including the GaGog reservoir located in Miryang city, Gyeongsangnam province in South Korea, where there is actual survey information, were selected. A multiple regression model was developed in consideration of physical and climatic characteristics, and a total of four empirical formulas and sediment deposition rate were calculated. Using this, the error of the sediment deposition rate was compared. As a result of calculating the sediment deposition rate using the multiple regression model, the error was the lowest from 0.21(m³km²/yr) to 2.13(m³km²/yr). Therefore, based on the sediment deposition rate estimated by the multi-regression model, the change in the available capacity of reservoir wetlands was analyzed, and the effective storage capacity was found to have decreased from 0.21(%) to 16.56(%). In addition, the sediment deposition rate of the reservoir where the overflow damage occurred was relatively higher than that of the reservoir where the piping damage occurred. In other words, accumulating sediment deposition rate at the bottom of the reservoir would result in a lack of acceptable effective water capacity and reduced reservoir flood and drought control capabilities, resulting in reservoir collapse damage.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.2
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• pp.87-93
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• 2009

The labyrinth weir can be defined that the plane shape of overflow part is not straight line and is a kind of weir having overflow length increased by changing its plane shape. Recently, the labyrinth weir can be widely applied to various hydraulic facilities such as dam spillway, irrigation facilities, and canal structures by increasing precipitation. This study was performed to analyze the hydraulic characteristics according to triangle labyrinth weir using hydraulic model experiments and finally estimate the discharge coefficients for triangle labyrinth weirs. The formulae of discharge coefficient provided in this study, which make it feasible to calculate the overflow rate by a coefficient of correlation. sum of residuals, MAPE(Mean Absolute Percentage Error), are expected to be widely applied to design of hydraulic facilities such as dam spillway and irrigation system.