• Journal of Bio-Environment Control
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• v.25 no.1
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• pp.63-70
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• 2016

Water drainage from the open hydroponics often causes significant environmental pollution due to agrochemicals and loss of water and nutrients. The objectives of this study were to show the potential application of an irrigation schedule based on threshold values of volumetric substrate water content for tomato (Solanum lycopersicum L. 'Samsamgu') cultivation in a commercial hydroponic farm during spring to summer cultivation. This study was performed for minimizing effluent from coir substrate hydroponics using a frequency domain reflectometry (FDR) sensor-automated irrigation, as compared with an integrated solar-radiation (IR) and conventional timer-irrigation (TIMER) after transplanting. In results, no significant difference in daily irrigation volume was found among the treatments until 88 days after transplant (DAT). However, during the 88 to 107 DAT, the daily irrigation volume was in the order of IR (2125 mL) > TIMER (2063 mL) > FDR (1983 mL), and during the 108 to 120 DAT, it was in the order of IR (2000 mL) > TIMER (1664 mL) > FDR (1500 mL). The lowest drainage volume was observed in the FDR treatment with the order of IR (12~19%) > TIMER (4~12%) > FDR (0~7%) during the entire growing period. A lower irrigation volume in the FDR treatment after 88 DAT may be due to the sensor's detecting capacity for less water absorption by plant after completing fruit maturity with apical pruning and removal of lower leaves, while a higher irrigation volume in the IR treatment may be due to gradual increase in integrated solar-radiation amount as closer to summer season. There was no significant difference in plant growth and fruit yield among the treatments; however, a 11% and 18% of higher soluble sugar content was observed in the FDR than that of TIMER and IR treatment. respectively.

• Journal of the Korean Institute of Landscape Architecture
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• v.14 no.1
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• pp.1-13
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• 1986

The purpose of this study is to investigate the effect of temperature control by a shade tree and the lawn area. In this investigation, we find out that artificial-lawn, concerte, and exposed soil are more higher temperature than covered with plant materials. The results of the measurement may to summerized as follows; 1) Low-temperature effects of zoysia japonica is more controlled by condition of growth than leaf length of grass. Surface temperature make 0.7$^{\circ}C$ difference between long grass (15cm), and short grass (5cm), but make 5$^{\circ}C$ difference between good growth grass (230/10$\textrm{cm}^2$) and bad growth grass (80/10$\textrm{cm}^2$). 2) The surface temperature of the lawn area is 40.5$^{\circ}C$ lower on a maxinum than that of the artificial lawn (July 28, 1985). During the day of summer, shade area under the shade tree is 0.9$^{\circ}C$ lower then lawn area surface temperature, 6.9$^{\circ}C$ lower than bad growth lawn, 10.3$^{\circ}C$ lower than exposed soil, and 18$^{\circ}C$ lower than concrete surface temperature. 3) Natural irrigation effect on the surface temperature fluctuation. But this effect is changed by compositions of ground materials and time-lapse. 4) Sunny day is more effective than cloud day. 5) In summer season, surface temperature make a difference compare to temperature of 0.5-1.5m height from ground : Surface temperature is 3.4$^{\circ}C$ lower at the lawn area (11 a.m.), 4.2$^{\circ}C$ lower at the shade area the shade tree, 12.7$^{\circ}C$ higher at the concrete area (3p.m.), 38.8$^{\circ}C$ higher at the artificial lawn (2p.m.) 6) According to compositions of ground materials and season have specific vertical temperature distribution curve. 7) In summer season, temperature distribution of 0.5-1.5m hight at the shade tree is 4.8-5.7$^{\circ}C$ lower than concrete area (noon-3p.m.)

• Korean Journal of Environmental Agriculture
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• v.21 no.4
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• pp.243-247
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• 2002

Irrigation water quality along Donjin river watershed was monitored to find a possible pollutant, for maintaining water quality to achieve food safety through water quality preservation of river. As a pollution indicators, such as Biological Oxygen Demand(BOD), Chemical Oxygen Demand(COD), Total Nitrogen(T-N), and Total Phosphate(T-P) in Dongjin river were examined from May to November in 2001. The results were as follows : The BOD level of Dongjin river ranged from 2.84 to 6.45 mg/L, which would be in a II$\sim$IV grade of the potable water criteria by Ministry of Environment. Averaged BOD level of downstream DJ6(After Jeongupcheon confluence) was 4.07 mg/L. The average COD level of Dongjin river ranged from 11.20 to 32.96 mg/L. COD level of DJ6 rapidly increased rapidly after the junction of Dongjin river and Jungupcheon because it showed the latter had relatively high pollution level. T-N content were significantly high in all sites of Dongjin river ranged through 4.16 to 5.84 mg/L. T-P examined high concentration than another thing point by 0.19 mg/L after Jeongupcheon confluence as BOD and COD. COD of main stream was expressed high concentration to dry season after rainy season. In case of T-P, pollution degree of dry season before rainy season appeared and examined that quality of water was worsened go by dry season after rainy season. The water quality of Dongjin river was deteriorated with inflow of Jungupcheon polluted by municipal and industrial sites near Jungup city.

• Horticultural Science & Technology
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• v.32 no.1
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• pp.18-25
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• 2014

This study was conducted to investigated effects of water relation of mulching and trickle irrigation on the external and internal fruit quality in Satsuma mandarin grafted on trifoliate orange rootstock in a orchard assigned to randomly three groups; whole period of Tyvex mulching (TM), Tyvex mulching with trickle irrigation once a week from October 22 to harvesting season (WM) and non-mulching treatment (NM). The average soil moisture content in the TM was lower than the WM during the time of trickle irrigation from Oct. 21 to Nov. 28. The leaf water potential was at the level of ${\Psi}max$ of -1.5 to -2.5 MPa during whole period of Tyvex mulching treatment but gradually increased at the point of supplement of water. The water and osmotic potential in juice vesicle was decreased by drought but increased again in response to the supply of water in WM. The total soluble solids (TSS) in fruit juice was increased by drought stress, but diminished in response to supply of water after drought. The content of titratible acidity was increased by drought stress but gradually decreased due to supplement of water after drought, reached it at the level of 1%. It was suggested that the accumulation of the total soluble solids compensates the degree of active osmoregulation and the decrease in content of acidity accounts for the fast respiration and water uptake resulted of the water after drought.

• Journal of Korean Society of Forest Science
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• v.97 no.1
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• pp.53-60
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• 2008

This study was carried out to investigate the optimum management system during a overwintering for the production of Pinus densiflora container 2-0 seedlings. The experiment performed between 2005~2006 in a polyethylene film house (PE house) located at Yeoju-Gun in Kyungki-Do. During the winter in the PE house, the difference in maximum day temperature and minimum day temperature was large, and the difference in temperature was detected between the container keeping locations. During the winter season, the maximum day temperatures at the seedling bench in January and February were $32.8^{\circ}C$ and$36.6^{\circ}C$, respectively, whereas those at the ground in January and February were $16.0^{\circ}C$ and $24.4^{\circ}C$, respectively. Water contents of container seedlings was reduced gradually from the beginning the experiment, and reduced rapidly from February to March, and increased rapidly from April. Container seedlings showed different death rate according to the extending of the irrigation cycle. Death rate by one week and two weeks of irrigation cycle was 4.8% and 6.5%, and 38.5% and 49.4% of death rate occurred by three and four weeks of irrigation cycle, respectively. It is suggested that the proper irrigation cycle for P. densiflora 2-0 container seedlings during overwintering is two weeks. When containers placed directly on the ground, the root of container seedlings went out through the drainage of the container, and grew out in the soil. These roots were cut while moving the container to the bench in spring.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.830-833
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• 2004

Hydraulic structures have been constructed with low cost concrete so as to increase the investment efficiency. But, it has caused to produce structures having excess internal voids inside concrete. As the construction of agricultural irrigation and drainage project is concentrated on off-farming season and scattered in wider area, variation of quality of structures is big and it caused increase of internal voids. Due to that reason, hazardous substance is passing rather freely through the voids causing occur of crack and accordingly life time of structures is getting shortened. It is necessary to make a thesis of design criteria for design strength to increase life time, range of variation of quality, strength of ready-mixed concrete proper to design strength, and water-cement ratio and air content.

• KCID journal
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• v.14 no.2
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• pp.181-193
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• 2007

The characteristics of non-point source pollutant loads in middle-stream of Nakdong River Were studied through analysis of pollutant loads of 8 sub-watersheds divided based on administrative district. The pollutant concentration of each sub-watershed was collected from Nakdong-River Water Research Institute and Daegu Regional Environmental Office, respectively. Pollution items analysed in this study were BOD, SS, T-N and T-P. High degree of non-point pollution was observed from Gumi, Goryeong, Gyeongsan, Daegu and Sungju, and pollution was usually increased during rainy season. This result indicates that a given pollution condition within the watershed can be more sensitive than location factor to the level of water quality. The main sources of non-point pollution were population and livestock, as well as landuse factor, and were found to significantly contribute to the water pollution. Alternative solutions for controlling pollution sources, therefore, should be provided to meet target levels of water quality in this region.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.137-140
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• 2004

Hydraulic structures have been constructed with low cost concrete so as to increase the investment efficiency. As the construction of agricultural irrigation and drainage project is concentrated on off-farming season and come to construction less than 28-day strength in quality control. As we are aware the major thrust construction of short period is now in hydraulic structures rather then the large- scale. This paper will propose the relationship between the 7-day and 28-day compressive strength of concrete be investigated. Test will be carried out on nine different concrete mixes and 180 core drilled form the hydraulic structures with 7-day and 28-day compressive strengths ranging approximately from 24 to 30Mpa.

• Korean Journal of Environmental Agriculture
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• v.16 no.4
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• pp.394-398
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• 1997

Changes of nutrient material and heavy metals of irrigation water and natural supplies by irrigation water into 1.0ha of paddy field during the rice cultivation was investigated pH of irrigation water ranged 6.458.34 and electrical conductivity showed $110{\mu}S/cm$ in the first irrigation period and commonly showed $90{\mu}S/cm$. The content of T-N, NH4-N and $NO_3-N$were 3.09~12.36, 0.17~1.34 and 2.70~10.72mg/L respectively. The content of T-P was 0.09~0.22mg/L and ortho-P was not detected. The content of $Ca^{++},\;Mg^{++},\;Na^+\;and\;K^+$ showed 0.89~5.12, 1.12~2.76, 1.74~4.52 and 1.34~4.18mg/L regardless of irrigation season respectively. Only Cu and Zn of heavy metals were detected 0.001~0.009 and 0.007~0.091mg/L, but Pb, Cd, Cr and Ni were not detected When supplied $4,250m^3$ of an irrigation water into 1.0㏊ of paddy field, natural supplies of nutrient materials were 29.67㎏ of T-N, 1.80㎏ of $NH_4-N$, 24.57kg of NO3-N and 0.51kg of T-P. Also $Ca^{++},\;Mg^{++},\;Na^+,\;K^+,\;Cl^-\;and\;SO_4\;^{2-}$ were supplied 9.42, 7.09, 13.34, 9.08, 40.27 and 41.38kg respectively. Only Cu and Zn of heavy metals were supplied 0.017kg of Cu and 0.133kg of Zn, Pb, Cd, Cr and Ni were not supplied

• Korean Journal of Environmental Agriculture
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• v.18 no.1
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• pp.6-7
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• 1999

The water quality at Mankyeong River was surveyed 13 sites of main stream for 6 months from April to September in 1995 and 1997. The monthly average value of $NH_4-N$, $SO_4^{2-}$ and $Cl^-$ showed the highest peak in April while that of $NO_3-N$ showed the highest peak in August. The monthly average value of COD showed the highest peak in September at high temperature season. Concentrations of $NH_4-N$ and $SO_4^{2-}$ in Mankyeong River stream exceeded the standard water quality criteria in many sites. The water quality of Mankyeong River stream was not suitable for the irrigation source excepted the sites such as Hari, Gosan stream and Soyang stream. The floodgate of Mokcheon, Yocheon, Jeonju and Samcheon stream were rapidly polluted by the sewage of city, otherwise the Iksan stream was rapidly polluted by the sewage of swine. The sum of ionic concentrations in Mankyeong River stream was the highest at floodgate of Yocheon by influence of the sewage from city and industry. The order of the major anions and cations concentration in Mankyeong River stream were $SO_4^{2-}$ > $Cl^-$ > $NO_3-N$ > $SO_4^{3-}$ and $Na^+$ > $Ca^{2+}$ > $NH_4^+$ > $Mg^{2+}$ > $K^+$, respectively.