• Korean Journal of Organic Agriculture
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• v.27 no.2
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• pp.173-191
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• 2019

The study was initiated to compare seasonal nutrient variations and rice (Oryza sativa L.) productivity in each of leading rice farm with conventionally managed and recommended fertilized of the large-scale environment-friendly agricultural districts in Jangheung, Suncheon, and Okcheon provinces in 2017. Suncheon rice experimental farm plots included a recommended fertilization plot that had been additionally sown hairy vetch in the fall of previous year, while Okcheon rice farm included a recommended fertilization plot applying half amount of the compost in the conventional plot. A Jangheung rice farm only practiced crop-livestock farming system. Soil pH and EC in all experimental plots were suitable levels for rice growth to cultivate. Seasonal soil pH from March to September was the highest for Suncheon rice farm, and seasonal soil EC was the highest for Jangheung rice farm. Seasonal soil T-N increased in all the plots from March to June in particular for Suncheon rice farm, and Jangheung rice farm had the lowest seasonal soil P. Seasonal soil K decreased in all the plots, with the lowest levels observed for Okcheon farm. Seasonal soil NH₄⁺ mostly increased by up to 90 mg/kg in Jangheung rice farm from March to June. Seasonal plant T-N, P and K concentrations were the highest for Jangheung rice farm. Seasonal plant T-N and P concentrations decreased from June to September, but K leveles were fluctuated between 2.0% and 2.5%. Seasonal SPAD value was the lowest in Suncheon conventional plot. Jangheung rice farm plot produced 6,303 kg of rice per ha, which was approximately two times higher than those of Okcheon recommended plot. The seasonal T-N, P and K balance was the highest in Okcheon conventional plot, with the lowest values observed for Suncheon conventional plot. As a result, Suncheon recommended plot showed relatively low levels of seasonal macro-nutrient balance and the highest rice production, which could be the most environmentally friendly farm practiced conducted in this study.

• Horticultural Science & Technology
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• v.35 no.1
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• pp.69-78
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• 2017

This study was conducted to investigate the effects of waterlogging on the net photosynthetic rate, root activity and fruit yield of hot pepper. Plants were grown in two greenhouses: extractor fans and side ventilators began to operate when the inside temperature reached $25^{\circ}C$ in one greenhouse and $35^{\circ}C$ in the other. Waterlogging treatments were performed 54 days after transplanting (when fruit setting at the second flower truss was complete). The plot in each greenhouse was divided into five sections, and each section was watered for 0, 12, 24, 48 or 72 h using drip irrigation. Plants under $25^{\circ}C$ and non - waterlogging treatment exhibited in the greatest growth among treatments. Plant growth generally decreased as the waterlogging period increased. The net photosynthetic rate was highest under non - waterlogging and $25^{\circ}C$ treatment and lowest under 72 h waterlogging and $25^{\circ}C$ treatment. The root activity decreased as the waterlogging period increased, except for plants under 72 h waterlogging treatment at $35^{\circ}C$. The number and weight of red pepper fruits per plant were highest under non - waterlogging treatment at $35^{\circ}C$. The greatest fruit yield was also observed under non - waterlogging treatment at $35^{\circ}C$, with production reaching 3,697 kg / 10a. At the appropriate temperature for hot pepper ($25^{\circ}C$), yields were reduced by 25 - 30% under 12, 24 and 48 h waterlogging treatment compared to non - waterlogging treatment. These results indicate that longer waterlogging periods reduce the growth, net photosynthetic rate, root activity and yields of hot pepper. However, the net photosynthetic rate and stomatal conductance of hot pepper plants grown under 72 h waterlogging treatment recovered nine days after growth under normal growth conditions.

• Korean Journal of Ecology and Environment
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• v.41 no.2
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• pp.216-227
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• 2008

To understand eutrophication in the upper regions of brackish Lake Sihwa with a limited water exchange, temporal and spatial distributions of pollutants in water and sediment were investigated from March to October in 2005 and 2006. Also, pollution levels of water and sediment were estimated by trophic state index (TSI) and sediment quality guideline (SQG). Total nitrogen (TN), total phosphorus (TP), organic matter (COD), and chlorophyll $\alpha$ (Chl-$\alpha$) concentrations in the surface waters were largely varied temporally and spatially, and the variations were highest in the middle areas where strong halocline was formed. Chl-$\alpha$ concentrations in the middle area were very high in April (>$900\;{\mu}g\;L^{-1}$) when algal blooms (red tides) occurred. The relationships between TN and Chl-$\alpha$ (r=0.31), and TP and Chl-$\alpha$ (r=0.65) indicated that the algal growth was primarily affected by phosphorus rather than nitrogen. The distribution of COD was similar to that of Chl-$\alpha$, indicating that the autochthonous organic matters may be a more important carbon source, especially in the middle areas. The brackish water regions were classified as eutrophic or hypertrophic based on their TSI values ($69{\sim}76$). In addition, the content of nutrients (especially TP) in surface sediments were classified as severe polluted state, except the upper areas. Major causes of the eutrophication observed were probably due to high nutrients loading from watersheds, the phosphorus release from anaerobic sediment, and long retention time by the limited water exchange through the sluice gates.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.5
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• pp.439-458
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• 2013

Temporal and spatial variations of water quality were investigated in the Cheonsu Bay of Yellow Sea, Korea from 2010 to 2011. Water samples were collected at 16 stations and physicochemical parameters were analyzed including water temperature, salinity, suspended solids (SS), chemical oxygen demand (COD), dissolved oxygen (DO), Chlorophyll a and nutrients. Spatial distribution patterns of all survey items were not clear among stations but the bimonthly variations were distinct except the bottom water of the suspended solids. The trend analysis by principal component analysis (PCA) during 2 years revealed the significant variations in water quality in the study area. Spatial water qualities were discriminated into 3 clusters by PCA; station cluster in the surface water 1, 2~11, and 12~16, the bottom water 1, 2~7, and 8~16. Annual bimonthly water qualities were clearly discriminated into 3 clusters by PCA. But tend of cluster in the surface and bottom water was difference, period most of the research was low in nutrient. Ecology-based water quality criteria was a good level of grade II. Bimonthly results are shown as III grade(normal) at June and August, II grade(good) at October and December and I grade for February and April. Water quality was showed by the input of fresh water same as those of Kyoungin coastal area, Asan coastal area, Gunsan coastal and Mokpo coastal area in the Cheonsu.

• Journal of Bio-Environment Control
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• v.31 no.1
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• pp.67-76
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• 2022

This study aimed to determine the photosynthesis and growth characteristics of Peucedanum japonicum T. grown under aquaponics in a plant factory (AP) by comparing those grown under hydroponic cultivation system (HP). The AP system raised 30 fishes at a density of 10.6 kg·m^-3 in a 367.5 L tank, and at HP, nutrient solution was controlled with EC 1.3 dS·m^-1 and pH 6.5. The pH level ranged from 4.0 to 7.1 for the AP system and 4.0 to 7.4 for the HP system. The pH level in the AP began to decrease with an increase in nitrate nitrogen (NO₃-N) and lasted bellower than pH 5.5 for 15-67 DAT. It was found that ammonium nitrogen (NH₄-N) continued to increase even under low pH conditions. EC was maintained at 1.3 to 1.5 dS·m^-1 in both systems. The concentration of major mineral elements in the fish tank was higher than that of the hydroponics, except for K and Mg. There was no significant difference in the photosynthesis characteristics, but the PIABS parameters were 30.4% lower in the AP compared to the HP at the 34DAT and 12.0% lower at the 74DAT. There was no significant difference in the growth characteristics, but the petiole length was 56% longer in the leaf grown under the AP system. While there was no significant difference in the fresh and dry weights of leaf and root, the leaf area ratio was 36.43% higher in the AP system. All the integrated results suggest that aquaponics is a highly-sustainable farming to safely produce food by recycling agricultural by-products, and to produce Peucedanum japonicum as much as hydroponics under a proper fish density and pH level.

• Journal of Korean Society of Forest Science
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• v.111 no.3
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• pp.405-417
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• 2022

The purpose of this study was to describe the photosynthetic features of Prunus maximowiczii and Prunus serrulate Lindl. var. pubescens (Makino) Nakai in response to drought stress. Specifically, we studied the effects of drought on photosynthetic ability and photosystem II activity. Drought stress (DS) was induced by cutting the water supply for 30 days. DS decreased the moisture contents in the soil, and between the 10th and 12th days of DS, both species had 10% or less of x., After the 15th day of DS, it was less than 5%, which is a condition for disease to start. We observed a remarkable decrease of maximum photosynthesis rate starting from 10th day of DS; the light compensation point was also remarkable. Dark respiration and net apparent quantum yield decreased significantly on the 15th day of DS, and then increased on the 20th day. In addition, the stomatal transpiration rate of P. maximowiczii decreased significantly on the15th day of DS, and then increased on the 20th day. Water use efficiency increased on the 15th day of DS, and then decreased on the 20th day. The stomatal transpiration rate of P. serrulate decreased significantly on the 20th day of DS, and then increased afterward, while its water use efficiency increased on the 20th day of DS, and then decreased afterward. These results indicate that the closure of stoma prevented water loss, resulting in a temporary increase of water use efficiency. Chlorophyll fluorescence analysis detected remarkable decreases in the functional index (PI_ABS) and energy transfer efficiency in P. maximowiczii after the 15th day of DS. Meanwhile, photosystem II activity decreased in P. serrulate after 20 days of DS. In addition, Ts-Ta, PI_ABS, DI_O/RC, ET_O/RC followed similar trends as those of the soil moisture content and photosynthetic properties, indicating that they can be used as useful variables in predicting DS in trees.

• Food Science and Preservation
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• v.30 no.5
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• pp.833-846
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• 2023

Onions are essential vegetables for Koreans' diet and have various physiological activities. However, problems arise every year due to the imbalance between production and demand. Therefore, in this study, nutritional and functional components, and antioxidant activity were analyzed for each growth period in order to utilize onions at the disposal period. Whole onions harvested before June showed higher values of general ingredients, inorganic ingredients, organic acids, spiraeoside, quercetin, total chlorophyll, and antioxidant activity than bulbs harvested in June. On the other hand, the free sugar content was higher in the bulb of the harvest season in June than in whole onions. The total thiosulfinate content was similar to that of whole onions and bulbs in the early stages of growth. In addition, as a result of comparing the flavonoid compound and antioxidant activity of each onion variety, whole onions harvested at 25 weeks were higher in content than onion bulbs harvested in June. In conclusion, onions before the harvest season in June had excellent utilization value as food. Harvesting before 21 weeks is desirable for growing onions with excellent nutritional value, while harvesting after 23 weeks is recommended for excellent functional components and antioxidant activity in onions.