• Korean Journal of Medicinal Crop Science
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• v.20 no.3
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• pp.177-183
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• 2012

To develop the practical cultivation for paddy field, we investigated the properties of paddy soil, growth characteristics and ginsenoside content of 6-year-old ginseng, Cheonpung variety between poor drainage class (PDC) and imperfect drainage class (IDC). Groundwater level in PDC showed monthly small changes of 20~30 cm, while IDC showed monthly great changes of 28~71 cm depending on rainfall. Soil moisture content in PDC and IDC was 17.2%, 22.5%, respectively. Air temperature in IDC was lower than $0.3^{\circ}C$, while soil temperature was higher than $0.8^{\circ}C$ compare to PDC, respectively. Main soil color of PDC was grayish olive, while IDC was brownish olive. PDC showed yellowish mottles only at underground of 20~40 cm, while IDC showed that at underground of 30~90 cm. IDC showed lower pH, EC, potassium, calcium and magnesium content, but higher organic matter, phosphate, and iron content than that of PDC, respectively. All of EC, organic matter, potassium, calcium, and magnesium content were decreased, but iron content was increased at the subsoil layers of PDC. All of EC, organic matter, phosphorus, and potassium content were decreased, but calcium and magnesium content were increased at the subsoil layers of IDC. Root yield in IDC was more increased by 33% than that of PDC. The moisture content and rusty ratio of ginseng root in IDC were lower than that of PDC. Ginsenoside content in IDC was higher than that of PDC because the ratio of lateral and fine root showing relatively high content of ginsenoside was higher in IDC than that of PDC.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.50-50
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• 2022

Recently, the use of mulching film has increased in soybean cultivation. Polyethylene (PE) films and biodegradable films (BF) have the advantages of improving soil moisture retention, geothermal maintenance, and CO2 maintenance as well providing weed control. Furthermore, BFs are a material that can compensate for the shortcomings of PE because it has the ability to decompose naturally by soil microorganisms, sunlight, and geothermal heat. Many researches have been carrying out studies regarding the development of BFs for these very reasons. This study was conducted better understand which films are optimal for soybean cultivation after evaluations of soybean growth and film characteristics of various BFs. BFs Farmsbio (Farm Hannong), Heulgro Film (Sejin Bio), Vonto Film (Eco-Hansung), two unnamed biodegradable films (Seojin Bio and Taesung), and a PE film were used in this study. For the control plots, no mulching was used. Experimental fields were fertilized according to conventional cultivation methods, tilled, and then covered with either BFs or PE films. After 1 week, soybean (cv. Daechan) seeds were seeded. Germination rate and plant height were measured at weekly intervals after seeding. In addition, pH, EC, and decomposition and light transmittance levels of films were measured during the experimental period. Daily average temperatures and relative humidity in soils was measured during the experimental period. There was no significant difference in germination rates and plant height in both crops grown with BFs and PE films, but crops grown in the control plot had significantly lower germination rates and growth. Soil pH was not significantly different regardless of treatments (BF, PE, and non-mulching) at 14, 28, and 42 days after seeding. In general, the EC contents in the control plots was lower than in crops grown using BFs and PE films. With the exception of some BFs, light transmittance and decomposition levels of films did not, in general, increase up to 70 days after soybean seeding. Since this study is ongoing, we are continually investigating these parameters. The average daily moisture in soil was higher in crops grown with BFs and PE films than in the control plot. However, the daily average soil temperature was not consistent regardless of treatments. Therefore, the BFs used in this study can be used without negative impacts on soybean growth.

• Korean Journal of Environment and Ecology
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• v.29 no.6
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• pp.947-951
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• 2015

This study presents proper irrigation interval for the soil condition of green roof system and the smooth growth of the landscaping herbaceous plants available and reveal the need for irrigation in rooftop conditions. Twenty kinds of greenery plants are tested on ground paved wood panels where rain and wind shielder is installed. Before test, irrigation is conducted fully to experimental plants and then soil moisture in pot is measured after every ten minutes. In conclusion, it is suggested that the irrigation has to be carried out every 4~5 days in order to minimize water and heat stress of plants. Also, irrigation management is an essential prerequisite for good condition and the smooth growth of plants and environmental effects in green roof system.

• Korean Journal of Agricultural and Forest Meteorology
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• v.5 no.4
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• pp.233-237
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• 2003

This study was conducted to provide a rational forest management method for a natural oak (Quercus variavilis) forest stand in the central part of South Korea based on characteristics of growth and water relation parameters. Average volume per hectare was 175.1 ㎥ in the study site of oak stands. Basal area and volume of each direction appeared to increase as the slope direction moves from north to south, but annual mean increment and periodic annual increment of DBH for 10 years showed the lowest value at the southern aspect. Maximum water potentials measured between 12 and 14 o'clock were analyzed by direction and elevation in the oak stands. Water potential of oak decreased as the slope changed from the north to the south aspect and water potential increased at lower elevations. Soil water content for the oak stands tended to decrease as the aspect shifted from north to south. Water potential and soil moisture content were highly correlated. It appears that oaks have a higher moisture requirement at the southern aspect, because of stand density related to intraspecific competition.

• Atmosphere
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• v.23 no.1
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• pp.113-121
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• 2013

The objective of this study is to develop and evaluate the system to produce the real-time ensemble drought prediction data. Ensemble drought prediction consists of 3 processes (meteorological outlook using the multi-initial conditions, hydrological analysis and drought index calculation) therefore, more processing time and data is required than that of single member. For ensemble drought prediction, data process time is optimized and hardware of existing system is upgraded. Ensemble drought data is estimated for year 2012 and to evaluate the accuracy of drought prediction data by using ROC (Relative Operating Characteristics) analysis. We obtained 5 ensembles as optimal number and predicted drought condition for every tenth day i.e. 5th, 15th and 25th of each month. The drought indices used are SPI (Standard Precipitation Index), SRI (Standard Runoff Index), SSI (Standard Soil moisture Index). Drought conditions were determined based on results obtained for each ensemble member. Overall the results showed higher accuracy using ensemble members as compared to single. The ROC score of SRI and SSI showed significant improvement in drought period however SPI was higher in the demise period. The proposed ensemble drought prediction system can be contributed to drought forecasting techniques in Korea.

• Proceedings of the Korean Society of Crop Science Conference
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• 2023.04a
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• pp.79-79
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• 2023

With the development of digital technology, the size of the smart agriculture market at home and abroad is rapidly expanding. It is necessary to establish a foundation for sustainable precision agriculture in order to respond to the aging of rural areas and labor shortages. This study was conducted to establish an automated digital agricultural test bed for soybean production management using data suitable for agricultural environmental conditions in Korea and to demonstrate the field of leading complexes. In order to manage water smartly, we installed a subsurface drip irrigation system in the upland field and an underground water level control system in the paddy field. Based on data collected from sensors, water management was controlled by utilizing an integrated control system. Irrigation was carried out when the soil moisture was less than 20%. For effective water management, soil moisture was measured at the surface, 15cm, and 30cm depth. The main growth characteristics and yield, such as stem length, number of branches, and number of nodes of the main stem, were investigated during the main growth period. During the operation of the test bed, drought appeared during the early vegetative growth period and maturity period, but in the open field smart agriculture test bed, water was automatically supplied, reducing labor by 53% and increasing yield by 2%. A test bed was installed for each field digital farming element technology, and it is planned to verify it once more this year. In the future, we plan to expand the field digital farming technology developed for leading farmers to the field.

• Magazine of the Korean Society of Agricultural Engineers
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• v.27 no.2
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• pp.57-71
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• 1985

The characteristics of compaction and unconfined compressive strength were investigated by mixing with lime to all soils adjusted by given percentages of two kinds of clays to sand to obtain the most effective distribution of grain size and the optimum lime content for soil stabilization. In addition, unconfined compressive strength and durability tested by adding of sodium metasilicate, sodium sulfate, sodium carbonate, sodium gydroxide and magnesium oxide to lime-soil mixture mixed with 8 percent lime to adjusted soil having the mixing percentage of 60 percent of cohesive black clay and 40 percent of sand by weight to get the effect and the optimum content of chemicals. The results obtained were as follows; 1.With the addition of more lime, the optimum moisture content was increased, and the maximum dry density was decreased, whereas the more the amount of clay and the less was the maximum drt density. 2. In the soil having more fine grain size the unconfined compressive strength was larger in the earlier stage of curing period, in accordance with the longer period, the mixing percentages of sand to clay showing the maximum unconfined compressive strength, on the basis of 28-day strength, were 60% : 40% (black clay) and 40% : 60% (brown clay) respectively. 3. The reason why the soil adjusted with black clay was remarkably bigger in the unconfined compressive strength than ones adjusted with brown clay for all specimen of lime-soil mixture was the difference in the kind of clay, the amount of chemical compositions the value of pH. Black clay was mainly composed of halloysite that reacted with lime satisfactorily, whereas the main composition of brown clay was kaolinite that was less effect in the enhance of unconfined compressive strength. Also the difference of unconfined compressive strength was because black clay was larger in the amount of composition of calcium oxide and magnesium oxide in the value of pH affecting directly on the unconfined compressive strength of lime-soil mixture than brown clay. 4. In the lime-soil mixture mixed with 8 percent of lime to soil that mixing percentage of sand to black clay was 60% : 40%, on the standard of 7-day strength, the effect of chemical was arranged in the order of magnesium oxide, sodium carbonate, sodium sulfate, sodium hydroxide and sodium metasilicate. 5. The optimum amount of chemical being applicable to the maximum unconfined compressive strength of lime-chemical-soil mixture was 1 percent by weight for air dry soil in the case of adding sodium carbonated and 0.75 percent on sodium hydroxide, the unconfined compressive strength was increased continuously with increase of the amount of chemical up to 2 percent of chemical content is the lime-chemical-soil mixture added sodium metasilicate, sodium sulfate and magnesium oxide. 6. It was considered that the chemical played and accelerant role of early revelation of strength because the rate of increase of unconfined compressive strength of all of lime-chemical-soil mixtures was largest on the 7-day cured specimen. 7. The effect of test on freezing and thawing after adding suitable amount of chemical on the lime-soil mixture mixed with 8 percent of lime to soil that mixing percentage of sand to black clay was 60% : 40% was arranged in the order of magnesium oxide, sodium carbonate, sodium sulfate, sodium metasilicate and sodium hydroxide.

• Geomechanics and Engineering
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• v.38 no.2
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• pp.205-214
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• 2024

Permafrost refers to the condition where the ground is frozen. It is crucial to review and evaluate the ground's characteristics before construction. In this study, electrical resistivity surveying is chosen as the investigative technique to apply and illustrate the results on the state of permafrost ground and to summarize its applicability. Field experiments are conducted in the Yeoncheon area of South Korea, which has a freezing index of 522.6°C·days. The target area is categorized into two ground conditions: the first where the original ground freezes, and the second involves excavating the original ground up to a depth of 3 meters, backfilling it, and then artificially injecting fluid. Thus, frozen ground conditions are simulated under both natural and artificial circumstances. Electrical resistivity surveys are performed under both above-freezing and sub-zero temperature conditions, with the experiments conducted at sub-zero temperatures revealing relatively more high-resistivity zones due to the temperature conditions. In this area, the distribution of soil moisture content is also investigated using the Time Domain Reflectometry (TDR) technique. It is observed that the ground into which water is artificially injected had a relatively higher moisture content, although the difference is minor. Finally, a 3D map of the target ground is constructed based on the measured electrical resistivity values, and through this, the distribution of porosity, a crucial design parameter, is also depicted. This research demonstrates that the electrical resistivity technique can effectively evaluate the state of frozen and unfrozen ground and further suggests that it can detailed extract the characteristics of the target ground.

• Geomechanics and Engineering
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• v.8 no.1
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• pp.17-31
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• 2015

An experimental program was performed to study the effects of cement stabilization on the geotechnical characteristics of sandy soils. Stabilizing agent included lime Portland cement, and was added in percentages of 2.5, 5 and 7.5% by dry weight of the soils. An analysis of the mechanical behavior of the soil is performed from the interpretation of results from unconfined compression tests and direct shear tests. Cylindrical and cube samples were prepared at optimum moisture content and maximum dry unit weight for unconfined compression and direct shear tests, respectively. Samples were cured for 7, 14 and 28 days after which they were tested. Based on the experimental investigations, the utilization of cemented specimens increased strength parameters, reduced displacement at failure, and changed soil behavior to a noticeable brittle behavior.

• KIEAE Journal
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• v.10 no.4
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• pp.75-80
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• 2010

Generally, ground-source heat pump (GSHP) systems have a higher performance than conventional air-source systems. However, the major fault of GSHP systems is their expensive boring costs. Therefore, it is important issue that to reduce initial cost and ensure stability of system through accurate prediction of the heat extraction and injection rates of the ground heat exchanger. Conventional analysis methods employed by line source theory are used to predict heat transfer rate between ground heat exchanger and soil. Shape of ground heat exchanger was simplified by equivalent diameter model, but these methods do not accurately reflect the heat transfer characteristics according to the heat exchanger geometry. In this study, a numerical model that combines a user subroutine module that calculates circulation water conditions in the ground heat exchanger and FEFLOW program which can simulate heat/moisture transfer in the soil, is developed. Heat transfer performance was evaluated for 3 different types ground heat exchanger(U-tube, Double U-tube, Coaxial).