• The Korean Journal of Malacology
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• v.19 no.2
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• pp.161-169
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• 2003

Seawater and sediment quality analysed was calculated to examinate the present environmental characteristics and pollution load was also calculated to evaluate the effect of farming area on the coastal environment. The measurements for seawater quality demonstrate the coastal environment has relatively eutrophicated with significantly decreased DO (0.2-8.5 mg/l) and elevated COD (9.6-31.2 mg/l) in summer. It was also evident that the water quality in Jindong Bay has been influenced by residues tide from Masan Bay with high metal concentration in August of 2002. Annual total pollution load (land and farm-driven) was estimated at 37,316 ton (SS) /yr: 9,809 ton/yr (26.3%) of land-driven load, 23,576 ton/yr (63.2%) of coastal sedimentation and 3,932 ton/yr (10.5%) of feces of cultural organisms. When all ark shell seedling farms are permitted species conversion to ascidian farm, the pollution load would increase by 196%, which may be another source for accelerating the eutrophication of the environment in Jindong Bay.

• Journal of Biosystems Engineering
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• v.6 no.1
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• pp.15-27
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• 1981

In order to investigate on the field performance of 3.5PS power tiller and to obtain the optimum using conditions of it, this experiment has been carried on the plowing operation, the rotary harrowing operation and the ridging operation that compared 3.5PS power tiller(KC-450) with the existing 5PS(DT-40) and 8PS(DT-85) power tiller. It has been performed at Suck Jung-Dong, Ansung Country, from March to October in 1980. The results of this field test were obtained as follows; 1. The plowing performance of KC-450 tiller was found to be 125min/10a that was lower than that of DT-85 tiller by 26min/10a in the effective plowing speed 0.9m/sec. 2. The field efficiency of KC-450 tiller was the highest among the power tillers as to be 82 persent that was higher than that of DT-85 tiller by 5 persent in the effective plowing speed 1m/sec. 3. The rotary harrowing performances of DT-40 tiller and DT-85 tiller were higher than that of KC-450 tiller in the rotary harrowing operation of the same speed, and the field efficiency of KC-450 tiller and DT-40 tiller were higher than that of DT-85 tiller in the rotary harrowing operation. 4. The ridging Performance of testing power tillers were nearly equality in the ridging operation of the same speed, and the field efficiency of testing tillers were higher KC-450 tiller than DT-40 tiller, DT-40 tiller than DT-85 tiller. 5. The work performance of power tiller increased with increase in the size of field area. Work performance and field efficiency of KC-450 tiller were higher than other tillers below 8a in field size 6. DT -85 tiller was more useful in deep plowing depth. But below 8a in field size KC-450 tiller was more easily operated and its field efficiency was higher 7. KC-450 tiller should be more useful to operate in the small size field or in the small scale farming and for the cultivation of vegetables, gardening plants, medicinal herb and tobacco plants, or for the cultivation in vinyl house.

• Korean Journal of Agricultural and Forest Meteorology
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• v.20 no.2
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• pp.175-182
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• 2018

Knowledge of the optimum cultivation period for Chinese cabbage would help growers especially in spring in Korea. Growth and yield of Chinese cabbage in a temperature gradient chamber was evaluated for the growing periods of 64 days from three set of transplanting dates including March 6, March 20, and April 3 in 2017. Air temperature in the chamber was elevated step-by-step, by $2^{\circ}C$ above the ambient temperature. This increment was divided into three phases; i.e. low (ambient+$2^{\circ}C$, A), medium (ambient+$4^{\circ}C$, B), and high temperature (ambient+$6^{\circ}C$, C). The fresh weight of Chinese cabbage was greater under B and C conditions in the first period and A in the second period, which indicated that GDDs affected the fresh weight considerably. However, leaf growth (number, area, length, and width) did not differ by GDDs. Bolting appeared under A condition in the first period, which was caused by low temperature in the early growth stage. Soft rot was developed under C condition in the second period and all temperature conditions in the third period, which resulted from high temperature in the late stage. Fresh weight increased when GDDs ranged from 587 to 729. However, it decreased when GDDs > 729. The maximum expected yield (16.3 MT/10a) was attained for the growing period of 64 days from transplanting date during which GDDs reached 601. The GDDs for optimum cultivation ranged from 478-724 under which the yield was about 95% (15.5 MT/10a) of maximum fresh weight. Such an optimum condition for GDDs was validated at five main cultivation regions including Jindo, Haenam, Naju, Seosan, and Pyeongtaek in Korea. In these regions, GDDs ranged from 619-719. This suggested that the optimum GDDs for Chinese cabbage cultivation would range from 478-724, which would give the useful information to expect the cultivation periods for ensuring maximum yield.

• Journal of Animal Environmental Science
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• v.17 no.2
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• pp.123-130
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• 2011

This study was carried out to examine the effect of cattle manure and chemical fertilizer application on productivity and nutritive value of silage corn in the reclaimed paddy field of Sukmoon at Dangjin Province in Korea. The cultivars of silage corn used in this experiment were Kwangpyungok and Pioneer (P32B33). The fertilizer was applied according to recommended dose of application. The reclaimed paddy field of Sukmoon was created for farming in 1985 and approximately 5 to 10 years ago rice was cultivated in full-scale. Recently, reclaimed paddy field of Sukmoon has a limitation to cultivate the crops, due to increased salinity caused by drought and poor drainage system. The total area of reclaimed paddy field of Sukmoon was 305 ha, and silage corn was sown on 149 ha of the reclaimed paddy field in nine regions, such as Songsan 28 A and B, Songsan 27 A and B, Songsan 42 A, B and C, and Songsan 43 A and B. The productivity and nutritive value of corn were evaluated collected from each of nine experimental regions. Dry matter (DM) yields of P32B33 in Songsan 28 A and B, and Songsan 27 A were 13 to 15 ton/ha and it was increased 3 to 5 ton/ha as compared to those of Songsan 27 B. DM yields of Kwangpyungok in Songsan 42 A, and Songsan 43 A and B were 23 to 27 ton/ha and it was increased 15 to 16 ton/ha as compared to Songsan 42 A and B. The nutritive value of corn was not significantly different between Kwangpyungok and P32B33, but the yield of Kwangpyungok corn silage was higher compared to P32B33. Therefore, this study suggests that good drainage system is important to maintain normal growth and productivity of corn in the reclaimed paddy field.

• Korean Journal of Environmental Agriculture
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• v.30 no.2
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• pp.209-215
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• 2011

BACKGROUND: The paddy ecosystem is periodically disturbed with a relatively consistent cycle in short term. However, in long term aspect, the paddy as habitats of organisms has been affected by the change in farming practices. Accordingly, the composition and their densities of fauna species inhabiting the wet paddy has been changed. The geological distribution of a species is very helpful to understand the past and current status of habitats and biodiversity. METHODS AND RESULTS: We monitored 290 sites of open plain paddy or terraced valley paddy located in 138 cities or counties of South Korea and analyzed examine geological distribution of a taxon of freshwater invertebrates, diving beetles (Dytiscidae) which inhabited the paddy ecosystem. This survey was conducted from 2005 through 2007. The total species of diving beetles found in the paddy were identified to be 15 genus 26 species among the family of Dytiscidae. Among them, 24 species were found in the terraced valleys-in paddy fields, and 19 species were found in the open plain paddy fields. Eleven species of them were rarely found in the paddy. The average body size of the adult diving beetles of each species was between 2.0 and 35.0 mm. Most of the diving beetle species except for 11 species with rare frequency of occurrence were found in almost all sites of the terraced valley paddy fields but three species (Agabus browni, Agabus japnicus, and Ilybius apicalis) were not found in the open plain paddy fields. The species distributed relatively widely over some sites of the open plain paddy fields were Guignotus japonicus, and Rhantus pulverosus. Specifically, Ilybius apicalis was found in a specific region, the east-southern part of Korean peninsula, whereas Coelambus chinensis was found only in valley paddy field of the region where Ilybius apicalis was not found. Overall distribution range of diving beetles in open plain paddy fields was limited to few area than in terraced valley paddy fields. CONCLUSION(s): The differences in the range of distribution of diving beetles between terraced valley paddy fields and open plain paddy fields was thought to be the result of an complex action of physico-chemical environments such as annual water status and the degree of chemical application involving differences in the extent of disturbance of the paddy ecosystem, the connectivity of the paddy to an adjacent biotope, and interrelationships among competitors.

• Korean Journal of Environmental Agriculture
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• v.30 no.2
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• pp.153-159
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• 2011

BACKGROUND: This experiment was conducted to investigate the distribution and burden characteristics of heavy metal in the rainwater sampled at Taean area, in the middle part of Korea, from April 2002 to October 2003. METHODS AND RESULTS: The relationship between concentration of heavy metal and other chemical properties in the rainwaters was also evaluated. Chemical properties in the rainwater were various differences with raining periods and years. It appeared that a weighted average pH values of rainwater was ranged from 5.0 to 5.1. Heavy metal concentrations in the rainwater were ranked as Pb > Zn > Cu > Ni > As > Cr > Cd. As compared with heavy metal concentrations of rainwater in 2002, Cu, Pb, and Zn were higher than other elements in 2003. There were positive correlation between major ionic components, such as ${NH_4}^+$, $Ca^{2+}$, $Mg^{2+}$, $K^+$, $Na^+$, ${SO_4}^{2-}$ and ${NO_3}^-$, and As, Cd, Zn, Cr, and Ni concentrations in rainwater. For heavy metal distribution of rainwater, the order of average enrichment factor was Cd > Pb > As > Cu > Zn > Ni > Cr, and these were relatively higher than the natural components such as Fe, Mg and Ca. The monthly enrichment factor were relatively high, from August to October at Taean. The monthly amount of heavy metal precipitation was high in the rainy season from July to August because of great influence of rainfall. CONCLUSION(s): The results of this study suggest that the heavy metals(Cd, Pb, As, Cu, and Zn) of rainwater is strongly influenced by anthropogenic sources rather than natural sources.

• Korean Journal of Environmental Agriculture
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• v.28 no.2
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• pp.97-105
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• 2009

A constructed wetland which was composed of aerobic and anaerobic areas was evaluated for 3 years to effectively treat the sewage produced in farming and fishing communities. For 3 years in a constructed wetland, biochemical oxygen demand(BOD), chemical oxygen demand(COD), suspended solids(SS), total nitrogen(T-N), and total phosphorus(T-P) in effluent were 0.2${\sim}$11.8, 1.0${\sim}$41.9, 1.1${\sim}$6.5, 4${\sim}$60 and 0.02${\sim}$3.51 mg/L, respectively. Removal rate of BOD, COD and SS in effluent were 97, 92 and 99%, respectively, in the third year. As time goes by, removal rate of T-N and T-P in treated water in aerobic area and effluent were gradually increased in a constructed wetland. In the third year, removal rate in effluent were 62 and 73%, respectively. By the seasons, removal rate of BOD, COD, SS, T-N and T-P were 97${\sim}$98, 87${\sim}$91, 99, 43${\sim}$61 and 76${\sim}$86%, respectively. Removal rate of BOD, COD, SS and T-P were not affected by the seasons, but that of T-N in winter and spring were decreased than the other seasons.

• Korean Journal of Agricultural Science
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• v.7 no.1
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• pp.52-58
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• 1980

This study was conducted to detect copper which is considered in the soils of orchards, since copper fungicide has been applied to fruit trees. Soil samples taken from the fields of the chief producing districts of apple (Chungju, Yesan, Daegu), pear (Yangju, Bucheon, Seonghwan) and citrus (Seogypo in Jeju island) were analysed by an atomic absorption spectrophotometer. The results obtained were summarized as follows ; 1. In orchards of apple, the amount of copper of soils from Yesan, Chungju and Daegu were ranged 2.6-171.3ppm, 2.2-136.1ppm and 14.3-134.6ppm, respectively. Very little copper was detected from the soils in the field which has been cultivated for less than 20 years. About 100ppm and 130-170ppm of copper were detected in the field which has been cultivated for 30 years and for 50-60 years, respectively. Most of the copper was detected in the surface layer of soils (0-10cm), while very low content of copper was detected in the deeper layer of soils (10-20cm). 2. In orchards of pear, 20-30ppm of copper was detected from the surface of soils in the field which has been cultivated for more than 30 years and the highest level of copper, 36.8ppm, was detected from Yangju area. The amount of copper of soils from Yangju, Seonghwan and Bucheon were ranged 3.6-36.8ppm, 9.7-19.4ppm and 3.6-24.7ppm, respectively. 3. In orchards of citrus of Jeju island, only trace amount and 23-38ppm of copper were detected in the fields cultivated for 15 years and 20-30 years, respectively. The highest level of copper, 57ppm, was detected from the surface layer of soils in the field which has been cultivated for 35 years, but in most of the soil samples tested, only the natural background level of copper, about 20ppm, was detected. 4. The levels of copper residue in all the soil samples tested were lower than the tolerance level (125ppm of copper which is extracted in 0.1N-HCl solution), except those of copperr residue, 130-170ppm, that were detected from the orchards of apple which have been under cultivation for 50-60 years. Hence no problem for the farming could be speculated with the present concentration of copper analysed.

• Korean Journal of Soil Science and Fertilizer
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• v.39 no.5
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• pp.268-273
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• 2006

Soil loss induced by erosion has come to be a serious problem in Korea's sloped land since more than 70% of upland fields are located on the sloped land area. The purpose of this study was to investigate the phase of water flow in differently soil textured plot soil types by rainfall amount. Lysimeters with slope of 15%, 5 m in length, 2 m in width, and 1 m in depth were prepared and filled up with three different soil textures, such as sandy loam, loam, and clay loam, then relationships between seasonal rainfall and runoff, percolation were analyzed. Runoff and percolation rate were shown to increase linearly with increasing rainfall intensity in all the soil textures, but the starting threshold and increment rate in runoff and percolation occurrence were dependent differently upon soil textures. Percolation increment rate according to the increasing rainfall amount was 0.52, 0.36, and 0.57 for sandy loam, loam and clay loam soil respectively. The threshold rainfall amounts in which percolation occurs were 5.73 mm, 6.80 mm, and 12.86 mm for sandy loam, loam and clay loam respectively. Runoff increment rates were 0.42, 0.48 and 0.46 for sandy loam, loam and clay loam soil. The threshold rainfall amount in which runoff occurs was 10.50 mm in sandy loam, 7.76 mm in loam and 17.40 mm in clay loam. These different phases of water flow by soil texture could be used to suggest guidelines for the best management practice of the farming slope land.

• Horticultural Science & Technology
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• v.34 no.1
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• pp.195-205
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• 2016

Sugar beet cyst nematode, Heterodera schachtii, causes serious economic losses worldwide in Brassicaceae crops. In 2011, this nematode was first found in highland vegetable cultivation areas in Korea, and thereafter spread to the surrounding healthy Chinese cabbage fields. However, little has been documented on the biological and ecological characteristics of the sugar beet nematode in highland vegetable cultivation areas. In this study the dispersal of the sugar beet cyst nematode was examined, focusing on spreading through soil and/or water infested with the nematode. When farmers with work boots trampled on Chinese cabbage fields for 10 minutes, the number of cysts recovered from the soil attached to the working differed depending on the research sites. Under irrigation conditions of 2, 4, and 8 liters of water per $m^2$, the amounts of soils attached on the bottom of the work boots and the number of healthy cysts in the soils increased significantly with the increase in soil moisture, although the total number of cysts, eggs, and juveniles did not increase significantly. After driving on the farm road adjacent to cabbage fields infested with the sugar beet cyst nematode, cysts were also recovered from the soil attached to the vehicle's tires, suggesting that the sugar beet cyst nematode can spread to new fields through soil carried by vehicles and by farmers. An excavator and a motor truck could deliver 41 kg and 224 g, respectively, of soil on the shovel shoes and the wheels to other locations during the Chinese cabbage harvest, suggesting that farming equipment and transportation vehicles may be vital means by which the cyst nematode spreads to non-infested fields in the highland area of Korea. Runoff water also contained cysts, whose amounts increased after water irrigation onto the ridges to simulate rainy conditions, with no significant difference in the number of cysts with increasing amounts of irrigation water. All of these results confirmed that the sugar beet cyst nematode spreads through soil attached to work boots, harvesting tools, and transportation vehicles, especially during the harvest time, and through runoff water on rainy days. These observations suggest that personal sanitization and cleaning of working tools and vehicles are one of the most important means to prevent the dispersal of the sugar beet cyst nematode in fields.