• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.1
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• pp.21-30
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• 1991

In Summer, oxygen-deficient water masses were developed extensively in the closed eutrophic bays such as Chinhae Bay which results in mass mortality of marine organisms and severe decrease the production of the bay every year. Under the circumstances, this study was performed to investigate the oxygen depletion relating to eutrophication, and also to evaluate self-purfication capacity of Buk Bay by dissolved oxygen mass balance in 1988. The mean concentration of total inorganic nitrogen, phosphate phosphorus and chlorophyll-a were $11.06{\mu}g-at/l,\;0.80{\mu}g-at/l\;and\;1.11mg/m^3$ respectively, which were over eutrophication criteria. Oxygen-deficient water mass was formed in July with the minimum concentration of 2.08ml/l(mean) at the bottom of all stations and recovered slowly in August. The decay and reaeration coefficient calculated from dissloved oxygen sag curve were 0.222/day and 0.018ml/l/day, respectively. To maintain above 4ml/l of oxygen to prevent oxygen-deficient water mass, it is recommendable to supply as much as 0.856ml/l/day of dissolved oxygen or should be reduced the same mass loading of BOD from watershed by the construction of wastewater treatment plant.

• Journal of the Korea Organic Resources Recycling Association
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• v.24 no.3
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• pp.91-99
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• 2016

The objective of this study was to investigate characteristics of inorganic components contained in liquid fertilizer produced using fish meal under different condition. Addition of dry yeast to liquid fertilizer resulted in considerable change in pH and electrical conductivity(EC) value compared to other liquid fertilizers which have microorganisms additives. In addition, it was appeared that the dry yeast-added treatment had higher $NH_4-N$ concentration than other treatments. Addition of molasses resulted in low pH compared to the control which has no additives. The EC, concentration $NH_4-N$ and $P_2O_5$ were not significant difference according to addition of molasses. The pH and $NH_4-N$ concentration in liquid fertilizer containing 20% of fish meal was highest after fermentation process, and EC value increased as the content of fish meal increase. When Cucumber was cultivated using liquid fertilizer, there was no difference in growth between fish meal liquid fertilizer treatment and chemical fertilizers treatment. However, there was a difference in yield according to the supply amount of nitrogen during the growing season.

• Korean Journal of Organic Agriculture
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• v.20 no.2
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• pp.231-241
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• 2012

Farming using natural salts for supply of nutrients to crops is increasing recently. It is necessary to evaluate the salt accumulation in soil and the effects on crop growth by treatment of natural salt. This study was conducted at the organic cultivation fields which garlics were planted. The treatments were no natural salts (control) and plots applied 100~600 $kg\;ha^{-1}$ with natural salts. Soil samples were taken from the 0 to 25 cm depth at 12 and 107 day (harvest time) after natural salts application. The results showed that electrical conductivity (EC), exchangeable Na (Exch.$-Na^+$) and Cl- were increased by application of natural salts. But, pH and exchangeable cations ($K^+$, $Ca^{2+}$ and $Mg^{2+}$) had not significantly differences among treatments. In 300 $kg\;ha^{-1}$ plots of natural salt, the level of EC, Exch.$-Na^+$ and $Cl^-$ in top soil (0-5 cm) was were increased more 0.3, 3.7, and 12.7 times than control plot, respectively. EC, Exch.$-Na^+$, and $Cl^-$ were highest in the top 5 cm of soil and decreased with depth at 12 days after natural salts application, but were decreased in the plower layer (0-15cm) at the harvest time because they were leached with natural rain. An increasing the application level of natural salt resulted in increasing of sodium adsorption ratio, exchangeable sodium percentage, and percentage of soil dispersion. The concentration of nutrient uptake such as total nitrogen (T-N), chloride (Cl) in garlic had significant difference between control and plots applied with natural salts The content of T-N of garlic in plots with natural salt application was lower than control plot, but Cl is higher than control plot.

• Applied Biological Chemistry
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• v.24 no.1
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• pp.15-20
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• 1981

Changes of urease activity in plant leaves following foliar application of urea were investigated with soybean, rye, tomato, radish and cabbage which were actively growing in a field. In this experiment, the procedure of the enzyme assay included incubation of the reaction mixture at $60^{\circ}C$ for 3 hr in order to inactivate heat unstable enzmes which may utilize ammonia produced by urease. The leaves with urea application showed somewhat higher urease specific activities for 2-4 days immediately after the foliar spray as compared with controls. The most difference of the specific activies between urea treatment and control was usually observed 2 days after urea application regardless of the plants. The difference of the specific activities disappeared completely 4 or 5 days following urea treatment. Protein contents in the leaves of soybean and tomato were increased for about 5 days after urea treatment, while no significant difference was found with rye, radish and cabbage. Urea application showed slightly lower ammonia concentration in the leaves which had higher urease activities. These results suggest that foliar spray of urea is very effective when nitrogen supply is required for rapid growth.

• Korean Journal of Agricultural and Forest Meteorology
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• v.21 no.4
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• pp.269-276
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• 2019

A semi-greenhouse experiment with field grown soybean (Glycine max L. cv Deawon, Uram, Jinpong, Soyon, Pungsangnamul, and Haewon) was performed in 2018. The experiment was aimed to investigate individual impacts of drought stress on soybean characteristic and seed yield. The three treatments were used in non-water stress (Control) during the soybean growth season, vegetative stage stress (VS), and flowering period stress (FS). Leaf number, LAI, leaf nitrogen concentration, and leaf biomass were decreased by drought at R4. In our study, the number of pods was 33.6% and 40.5% lower, respectively, in control than in VS and FS. In 100 seed weight, was 16.1% and 10.1% lower, respectively, in control than in VS and FS at R8. As a result, seed yield was 39.8% and 45.1% lower, respectively, in control than in VS and FS. Depending on the drought period, Daewon and Haewon showed a large decrease in yield, while Soyon did not change. The results of this study showed that flower and beginning pod setting stage responded more sensitively to the drought period than vegetative stage. Overall, these results demonstrate soybean seed yield formation more sensitive the during the flowing and beginning pod setting stage. We conclude that adequate water supply for pod setting stage, guaranteeing a high seed yield.

• Korean Journal of Environmental Agriculture
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• v.12 no.3
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• pp.247-254
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• 1993

The growth responses of Chinese Cabbage, lettuce, and spinach were evaluated to investigate the feasibility of carbonized rice-hulls as a sanitary cultivation media instead of soil. The carbonized rice-hulls were pretreated with several inorganic acid such as nitric, sulfuric, hydrochloric, and phosphoric acid for neutralization. The neutralization of the carbonated material using nitric, sulfuric, and phosphoric acid did not alter the growth responses of these vegetables compared to those of control plants grown on the normal cultivation soil. Especially, the nitric acid pretreatment resulted in the better growth of these plants than the mixture of soil and compost. This is probably due to the additional supply of the nitrate-nitrogens. However the growth responses of lettuce and spinach on the carbonated materials neutralized with hydrochloric acid were different and appeared to be having symptom which is analogous to the chloride toxicity during the late stage of growing. Although no difference was observed in chemical composition, the contents of protein-nitrogen were higher in the plants grown on the carbonated material compared to those of plant grown on the mixture of soil and compost. Based on our preliminary results, the carbonized and neutralized rice-hulls are very useful bed material for the sanitary cultivation under the controlled environmental condition.

• Korean Journal of Environmental Agriculture
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• v.31 no.1
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• pp.1-8
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• 2012

BACKGROUND: Organic fertilizers in watermelon cultivation are widely used to supply nutrient and organic matter. This study was conducted to investigate the effects of application rate of organic fertilizer on the watermelon growth and soil chemical properties in greenhouse METHODS AND RESULTS: The organic fertilizers used in this experiment were mixed expeller cake (MEC) and mixed organic fertilizer (MOF). The treatments were conducted with 4 levels (1.0 N, 0.7 N, 0.5 N and 0.3 N) on the basis of soil testing nitrogen fertilization (STNF) using MEC or MOF as the basal dressing, and using chemical fertilizers (CF) as the additional dressing on the rest of STNF. These fertilizations were compared to CF 1.0 N (0.3 N as the basal and 0.7 N as the additional dressing) and non fertilization (NF). The leaf area of watermelon in treatment 0.5 N and 0.3 N using MEC or MOF was similar to CF treatment. The absorbed nutrient amounts by leaf, weight and sugar contents of fruit in the 0.5 N and 0.3 N treatments were higher than other treatments. In 0.5 N and 0.3 N treatments using MEC or MOF on the basis of STNF, soil chemical properties such as electrical conductivity (EC), available $P_2O_5$ and exchangeable K concentrations after experiment showed tendency to decreasing or similar level before experiment. CONCLUSION(s): These results suggest that the MEC or MOF application as the basal dressing at the 30~50% level of STNF and CF application as the additional dressing on the rest of STNF be best to maintain adequate nutrient of soil and to increase marketable yield for watermelon.

• Journal of Energy Engineering
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• v.26 no.3
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• pp.105-112
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• 2017

A lot of piping systems have been used from nuclear power systems to water supply systems. The maintenance of the piping systems is needed to ensure proper operation of the piping systems. Failure of the large pipe systems especially such as KDHC(Korea District Heating Corporation) can be a matter directly related to the enterprise productivity and profitability. It can also lead to very important issues in promoting public safety and convenience. Therefore a method of quick and safety repairs have been emerged as the most important problem. In this study, freezing seal isolation method using liquid nitrogen cryogenic refrigerant was developed for the maintenance of a pre insulated heat transport pipe of KDHC with a diameter of 300 mm. In this study, by employing computational analysis techniques we performed the flow and heat transfer analysis for the targeted pre insulated heat transfer pipe and freezing seal jacket(ice-Plug) and have selected for optimal system. The detailed design model based on the results of the computational analysis finally was produced. A laboratory-scale test apparatus were designed and the freezing seal isolation self-test carried out. Also the performance assessment tests in the test bed of KDHC were carried out for on-site application.

• Journal of Korean Society of Forest Science
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• v.89 no.2
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• pp.185-197
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• 2000

This study was carried out to research structure of forest vegetation and site condition, and supply basic data for conservation of pine forest and ecologically sustainable forest management and control in Anmyondo area. The forest of Anmyondo were largely classified as four forest community : Pinus densiflora community, Pinus thunbergii community, Pinus rigida community, and Quercus variabilis community. Organic matter, total nitrogen, and other nutrients in soil of the study area were relatively low, and average soil pH was 4.9. Soil texture was sandy clay or heavy clay and so the aeration and permeability could be poor. In this study site, the methods such as the promotion of germination of pine seeds through removal of forest floor and inducement of natural regeneration through such method as regeneration under shelter wood would be better than the method such as afforestation after clear-cutting for conservation the pine forests. Also, it will be a good method to practice tending for hardwood species in the dominant areas by hardwood species.

• Journal of Wetlands Research
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• v.11 no.1
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• pp.115-121
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• 2009

The hybrid constructed wetland(HCW) as tertiary treatment process of a bio industrial wastewater treatment plant was employed to estimate applications for the reuse of final effluent. Raw wastewater was sequently treated through chemical and biological treatment processes and the biologically treated water was flowed into the HCW. The HCW system was composed of two constructed wetlands connected in series; The one is the aerobic constructed wetland with natural air draft system whose driving force for air supply was the difference between the temperature of the air inside the wetland and the ambient air, and the other is the anaerobic/anoxic constructed wetland. Average influent concentrations of BOD, SS, T-N and T-P in the HCW were 53mg/L, 48mg/L, 34mg/L and 3mg/L, respectively. After being treated at HCW, final effluent concentrations of BOD, SS, T-N and T-P were 2.3mg/L, 1.2mg/L, 7.95mg/L and 0.83mg/L, respectively. Referring to a reuse standard for a sewage wastewater, final effluent could sufficiently be reuse as landscaping, washing or agriculture water. HCW system with the aerobic/anaerobic combined constructed wetland could be achieved a high removal efficiency because each constructed wetland was functionalized to be removed efficiently organics, nitrogen and phosphorus. HCW system could be estimated to be successful application as tertiary treatment process of a various industrial and municipal wastewater.