• Journal of Biosystems Engineering
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• v.42 no.4
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• pp.276-282
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• 2017

Purpose: This paper presents the effects of soil drought stress during the growing season and pre-harvest period on tree growth and fruit quality of "Yumi" peach, an early season cultivar. Methods: Soil drought stresses were treated with four levels of -30, -50, -60, and -70 kPa during long term (LT) and short term (ST). For LT treatments, soil water was controlled for nine weeks from May 1 to July 5, which was assumed as the full growing season. For ST treatments, soil water was controlled for four weeks from June 10 to July 5, which was assumed as the pre-harvest season. Tree growth and leaf photosynthesis were measured, and fruit characteristics such as fruit weight and diameter, soluble solid and tannin contents, and harvest date were investigated. Results: Soil water deficit treatments caused a significant reduction in tree growth, leaf photosynthesis, and fruit enlargement. LT water stress over -60 kPa during the full growing season caused significant reduction in tree growth, including shoot length, trunk girth, leaf photosynthesis, and fruit enlargement. ST water stress over -60 kPa during the pre-harvest period also induced significant reduction in leaf photosynthesis and fruit enlargement, while tree growth was not reduced. In terms of fruit quality, water stress over -50 kPa significantly reduced fruit weight, increased soluble solid and tannin contents, and delayed harvest time in both LT and ST treatments. Conclusions: As a result, it is assumed that LT water stress over -60 kPa can reduce both tree growth and fruit enlargement, whereas ST water stress over -50 kPa can reduce fruit enlargement without reducing tree growth. From an agricultural perspective, moderate water deficit like -50 kPa treatments could have positive effects, such increased fruit soluble solid contents along with minimal reduction in fruit size.

• KSBB Journal
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• v.25 no.1
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• pp.103-107
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• 2010

Oil degradation agent was developed with organic sludge and modified peat moss (MPM) to recover oil contaminated soil. Waste sludge discharged from wastewater treatment plant of chemical plant in Ulsan National Industrial Park was used as organic sludge, and MPM was purchased. Organic sludge was adequate to use as growth medium for microorganism, the surface of MPM had porous structure which could enhance the cultivation condition of oil degradation microorganisms. Water contents and TPH variation with time were observed to investigate the degradation capacity of developed degradation agent. Water contents were rapidly decreased with higher contents of MPM, however, in case of TPH, high MPM content decreased the degradation capacity. Therefore, it was recommended that the content of MPM was controlled to below 10% in degradation agent as mixing organic sludge with MPM.

• Journal of the Korean Society of Tobacco Science
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• v.4 no.2
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• pp.3-10
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• 1982

This experiment was conducted to study the effect of soil water potenial on the growth and internal changes of stressed plants. The experimental imposition of soil water potential ( $\Psi$soil) were -0.1 to -0.2, -0.2 to -0.5, -0.5 to -3.0, -3.0 to -10.0 bar respectively. During water stress all growth rates were depressed, and the most sensitive period to water stress was found to be 10 to 25 days after transplanting. The water potential of leaf was declined rapidly within 12 hours after with holding of water. Nitrate reductase activity was decreased progressively as water deficit was built up in tobacco leaves, but the activity of alpha- amylase and super contents were increased. There were differences in peroxidase isozyme patterns between tile control and water stressed plant. New isozymes started to appear as tobacco leaf water potential decreased.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.1
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• pp.153-162
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• 2023

It is important to determine water movement at the growing substrate used in soil-less cultivation for better management of water supply. Numerical simulation is a fast and versatile approach to evaluate highly accurate water distribution. The objective of this study is to simulate the water movement in rockwool as a soil-less medium using HYDRUS-2D. HYDRUS-2D was used to simulate the spatial and temporal water movement in two types of rockwool slabs (Floriculture (FL), high density; Expert (EP), low density). The simulation was performed at two pulse conditions: 10 min ON and 50 min OFF (case A), 20 min ON and 40 min OFF (case B). The total irrigation amounts were the same at both cases. In case A, during the irrigation ON, the water contents at FL increased 1.93-fold faster than the values at EP. Whereas, during the irrigation OFF, the decreasing rate of water contents at FL was almost the same as one at EP. At case B, these values were not changed much from case A. However, the duration of optimum water content (50% - 80%) was 15.0 min and 23.5 min at case A and case B, respectively. Thus, FL and 20 min ON and 40 min OFF (case B) could supply water to rockwool much faster and longer than EP. Once qualitatively validated, this simulation of water movement in rockwool could be used to design an effective optimum irrigation method for vegetables.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.5
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• pp.372-378
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• 2015

Growing crops under different soil textures may affect crop growth and yield because of soil N availability, soil N leaching, and plant N uptake. The objective of this study was to evaluate effects of three different soils (sandy loam, loam, and clay loam) on cucumber (Cucumis sativus L.) yield, nitrogen (N) use efficiency (NUE), and water use efficiency (WUE) by subsurface drip fertigation in the greenhouse. Three different soil textures are sandy loam, loam, and clay loam with 3 replications. The dimension of each lysimeter was $1.0m(W){\times}1.5m(L){\times}1.0m(H)$. Cucumber was transplanted on April $8^{th}$ and Aug $16^{th}$ in 2011. The subsurface drip line and tensiometer was installed at 30 and 20 cm soil depth, respectively. An irrigation with $100mg\;NL^{-1}$ concentration was automatically applied when the tensiometer reading was 10 kPa. Volumetric soil water content for cucumber cultivation was the highest in 30 cm soil depth regardless of soil texture and was lowered when soil depth was deeper. The volumetric soil water contents at soil depths of 10, 30, 50, and 70 cm were the highest at clay loam, followed by loam, and sandy loam. The growth of cucumber at the $50^{th}$ day after transplanting was the lowest at sandy loam. Cucumber fruit yields were similar for all three soil textures. The highest amount of water use at sandy loam was observed. Nitrogen and water use efficiencies for cucumber were higher for clay loam, followed by loam and sandy loam, while the amount of N leaching was the greatest under sandy loam, followed by loam, and clay loam. Overall, growing cucumber on either loam or clay loam is better than sandy loam if subsurface drip fertigation is used in the greenhouse.

• Korean Journal of Environmental Agriculture
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• v.13 no.1
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• pp.10-17
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• 1994

To investigate differences with the polluted sources on Cu contents in soils and paddy rices under water pollutions, soils with the distance, the surface(0-15㎝ depth) and subsurface(15-30㎝ depth) in 1982 and 1990, and rice plants at the soil sampling sites in 1990 were separately sample at Mangyeong River area under the influence of municipal and industrial waste water from Jeonju city. Soil samples were extracted with $4M-HNO_3$ and plant samples were digested with mixture of $HNO_3$ and $HClO_4$ for analyzing Cu, Cd, Zn, Pb by atomic absorption spectrophotometry. Cu contents in soils ranged from 5.20 to 71.70 mg $kg^{-1}$. Average Cu level in 1990 was higher than that in 1982. Variation of Cu content with the distances from the source of waste water in 1990 was more regularly decreased than that in 1982. A significant correlation was observed between Cu contents in leaf sheath of rice plant and Cu, Zn and Pb contents in soils. Cu contents in soil was correlated with Zn and Pb in soil at area affected by waste water, regardless of years and soil depths. Cu contents in brown rice ranged from 0.4 to 10 mg $kg^{-1}$, and it was the lowest in parts of rice plant, and Cu content in panicle axis was 2.3 times higher than that in brown rice.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.593-596
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• 2008

The scour phenomenon involves the erosive potential of flowing water and the relative ability of the soil to resist erosion. The scour phenomenon in cohesive soils is much different from that in non-cohesive soils. Granular soils resist erosion by their buoyant weight and the friction between the particles. The soil particles are dislodged individually from the bed under the action of the eroding fluid. Scour in cohesive soils is much slower and more dependent on soil properties than that in non-cohesive soils. Therefore the analysis models for estimating erosion characteristics of cohesive soils should consider not only flowing water but also the relative ability of the soil to resist erosion. In this study, erosion characteristics for the clay-silt mixed soil will be analyzed as a fundamental study for development of bridge scour analysis and design system considering scour resistance capacity of a soil. For this analysis, the relationship between scour characteristics and soil properties was evaluated through scour rate test with Kaolinite samples remolded using various loading and contents of silt.

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.4
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• pp.365-374
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• 1999

To obtain informations on vertical movements of water and solute in rice paddy field during the growing season, soil water contents and bulk electrical conductivities (${\sigma}_a$) were monitored using Time Domain Reflectometry. Soil water contents with depth showed ${\varepsilon}$-shaped profiles constituting of partly saturated zones at top and bottom layers and unsaturated zones (20-100cm) between them. Analysis by fitting with a van Genuchten-type model showed that soil water contents at 60cm were affected by both water supplied from surface water and groundwater, but at 80cm mainly affected by groundwater. Water percolation at the rate of 2cm $day^{-1}$ rates were, but large fluctuation from 10 to 38cm $day^{-1}$ in C1 layer (60-90cm). Therefore, it can be said that any water or solute entering C1 layer is very rapidly transported to C2 layer, especially during the period of high groundwater table staying, and retarded to a relatively constant percolation rate in C2 layer. This can be manifested by the fact that rapid decrease and steady increase of electrical conductivities at 50 and 110cm depth respectively, were found around that period.

• Proceedings of the KSR Conference
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• 2000.11a
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• pp.410-417
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• 2000

The strength properties of Light-Weighted Soils(LWS) mixed with Expanded Polystrene(E.P.S.) using uniaxial and triaxial tests are studied. Test results show that when the initial water contents of dredged soils are under 135% and the cement contents are above 1%, Light-Weight Soils are in the appropriate strength range of 2.0 lo 4.0kg/$\textrm{cm}^2$. However. E.P.S. contents had a little effects on the strength properties of LWS.

• Journal of the Korean GEO-environmental Society
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• v.12 no.2
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• pp.23-33
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• 2011

In this paper, we got soil-water characteristic curve(SWCC) of Nak-Dong River's sand respectively as relative density 40%, 60%, 80% and content of silt 0%, 10%, 20%, 30%. As a result, the more the sand densify in the same silt content and the more the sand has silt in the same relative density, the change of volume water content was decreased. we have known effect of silt contents for SWCC and verified existing empirical formula of SWCC. As experiment results of soil-water characteristic curves compared to the empirical solutions, the results of van Genuchten(1980) and Fredlund & Xing(1994) were well-matched showing S type curves with experiment results. Especially the empirical solution of Fredlund & Xing showed almost same results of the coefficient of correlation($R^2$) equal to 0.99.