• KOREAN JOURNAL OF CROP SCIENCE
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• v.64 no.4
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• pp.422-431
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• 2019

Severe droughts in spring have occurred frequently in Korea in recent years, exerting a critical impact on corn yield. Therefore, it is necessary to find physiological and/or molecular indicators of the response to drought stress in maize plants. In this study, we investigated the effects of water-deficit stress on two Korean elite F₁ maize hybrids, Ilmichal and Gwangpyeongok, by withholding water for 10 days at tassel initiation. The water deficit drastically reduced the relative leaf water content, leaf number, leaf area, and stem length, leading to dry matter reduction. Moreover, it reduced the SPAD values and stomatal conductance of leaves in drought-stressed plants of both hybrids. Importantly, the number of leaves and SPAD value were non-destructive and easy to investigate in response to water-deficit stress, suggesting that they may be useful indicators for screening drought-tolerant genetic resources. We detected more than 100 spots that were differentially accumulated under drought stress. Of these spots, a total of 21 protein spots (≥1.5-fold) from drought-exposed maize leaves were successfully analyzed by MALDI-TOF-TOF mass spectrometry. Functional annotation using Gene Ontology analysis revealed that most of the identified proteins were involved in carbohydrate metabolism, stress response fatty acid catabolism, photosynthesis, energy metabolism, and transport. The protein expression levels were increased in both Ilmichal and Gwangpyeongok, except for triosephosphate isomerase, fructose-bisphosphate aldolase, and an uncharacterized protein. The lactoylglutathione lyase delta (3,5)-delta (2,4)-dienoyl-CoA isomerase was overexpressed in Gwangpyeongok only. The results obtained from this study suggest that the drought-specific genes may be useful as molecular markers for screening drought-tolerant maize genotypes.

• Korean Journal of Weed Science
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• v.18 no.2
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• pp.128-135
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• 1998

The experiment was carried out to obtain basic informations on sod culture using water foxtail in apple orchard at Kyeongbuk Provincial RDA in 1996 to 1997. Period of seedling emergence varied with sowing time and accumulative temperature. Sowing at Nov. 25 required longer than 100 days, while it needed only 8 days when water foxtail was sowed at Sep. 20. In a view of accumulative temperature, sowing at March 15 needed $139^{\circ}C$ but it required about $1,000^{\circ}C$ at August 10. This result showed that the seed of water foxtail has strong summer-dormancy in natural condition. Water foxtail had s-shape growth curve during growing season, and growth rate was the highest from March to May in this period. Plant height increased 2 times and 4 times for dry weight from March 20 to April 20. However, growth was decreased by summer depression after May. Major weeds in apple orchard were horseweed, akino-nogeshi and shepherd's-purse. These species were suppressed by the dominance of water foxtail. Water foxtail as a cover plant could be used for a method of weed control instead of herbicide in apple orchard.

• Journal of The Korean Society of Grassland and Forage Science
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• v.32 no.1
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• pp.1-8
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• 2012

This study was carried out in 2010 to investigate the utilization and forage quality of native grasses, such as $Phragmites$ $communis$ which might reduce the cost of feeding domestic cattle. The regions surveyed were the Haenam ranch in Haenam, Pyeongchang, Wonju, and Yeonggwang. In Haenam, yearly silage production harvested from 300 ha was 2,000 MT (7 MT/ha). All of those round bale silages were self-consumed in that region, and marketing price was 50,000~55,000 won per roll (110 won/kg). $Phragmites$ $communis$ of 150 cm in length contained 8.4% crude protein (CP) with relative feed value (RFV) 71.9 and 60.1% in vitro dry matter digestibility (IVDMD), which was somewhat more favorable than forage quality of rice straw. The silage quality of $Phragmites$ $communis$ varied greatly by the time of harvest (CP 4.7~6.4%, RFV 62.2~78.9, and IVDMD 41.9~53.9%), even with the same district and of the same original forage materials. Generally, the quality of $Phragmites$ $communis$ silage of was poorer than that of sorghum ${\times}$ sudangrass hybrid. In Pyeongchang, forage quality of $Phragmites$ $communis$ was decreased from 13.9% to 7.6% in CP, 90.7 to 76.1 in RFV, and 72.9% to 54.7% in IVDMD, as plant was getting mature, from 79 cm to 117 cm, 121 cm or to 142 cm in length. In Wonju, the quality values of $Phragmites$ $communis$ of 130 cm in length were 8.5% CP, 82.3 RFV and 70.2% IVDMD, while those of matured grasses of 220 cm in length were lower (10.2% CP, 65.1 RFV and 48.9% IVDMD), but this was a little more favorable than quality of rice straw. In Yeonggwang, feeding $Phragmites$ $communis$ was tried in a Hanwoo feed, but stopped due to low profitability. In conclusion, the overall quality of most native grasses including $Phragmites$ $communis$ in this survey was poor. Therefore, we recommend that $Phragmites$ $communis$ and native grasses should be harvested on June or July to obtain richer forage quality in forage values than rice straw.

• Korean Journal of Remote Sensing
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• v.23 no.6
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• pp.507-520
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• 2007

Satellite passive microwave(PM) sensors have been observing polar sea ice concentration(SIC), ice temperature, and snow depth since 1970s. Among them SIC is playing an important role in the various studies as it is considered the first factor for the monitoring of global climate and environment changes. Verification and correction of PM SIC is essential for this purpose. In this study, we calculated SIC from KOMPSAT-1 EOC images obtained from Arctic sea ice edges from July to August 2005 and compared with SSM/I SIC calculated from NASA Team(NT) algorithm. When we have no consideration of sea ice types, EOC and SSM/I NT SIC showed low correlation coefficient of 0.574. This is because there are differences in spatial resolution and observing time between two sensors, and the temporal and spatial variation of sea ice was high in summer Arctic ice edge. For the verification of SSM/I NT SIC according to sea ice types, we divided sea ice into land-fast ice, pack ice, and drift ice from EOC images, and compared them with SSM/I NT SIC corresponding to each ice type. The concentration of land-fast ice between EOC and SSM/I SIC were calculated very similarly to each other with the mean difference of 0.38%. This is because the temporal and spatial variation of land-fast ice is small, and the snow condition on the ice surface is relatively dry. In case of pack ice, there were lots of ice ridge and new ice that are known to be underestimated by NT algorithm. SSM/I NT SIC were lower than EOC SIC by 19.63% in average. In drift ice, SSM/I NT SIC showed 20.17% higher than EOC SIC in average. The sea ice with high concentration could be included inside the wide IFOV of SSM/I because the drift ice was located near the edge of pack ice. It is also suggested that SSM/I NT SIC overestimated the drift ice covered by wet snow.

• Journal of Korea Water Resources Association
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• v.52 no.11
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• pp.917-929
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• 2019

Denitrification in streams is of great importance because it is essential for amelioration of water quality and accurate estimation of $N_2O$ budgets. Denitrification is a major biological source or sink of $N_2O$, an important greenhouse gas, which is a multi-step respiratory process that converts nitrate ($NO_3{^-}$) to gaseous forms of nitrogen ($N_2$ or $N_2O$). In aquatic ecosystems, the complex interactions of water flooding condition, substrate supply, hydrodynamic and biogeochemical properties modulate the extent of multi-step reactions required for $N_2O$ flux. Although water flow in streambed and residence time affect reaction output, effects of a complex interaction of hydrodynamic, geomorphology and biogeochemical controls on the magnitude of denitrification in streams are still illusive. In this work, we built a two-dimensional water flow channel and measured $N_2O$ flux from channel sediment with different bed geomorphology by using static closed chambers. Two independent experiments were conducted with identical flume and geomorphology but sediment with differences in dissolved organic carbon (DOC). The experiment flume was a circulation channel through which the effluent flows back, and the size of it was $37m{\times}1.2m{\times}1m$. Five days before the experiment began, urea fertilizer (46% N) was added to sediment with the rate of $0.5kg\;N/m^2$. A sand dune (1 m length and 0.15 m height) was made at the middle of channel to simulate variations in microtopography. In high- DOC experiment, $N_2O$ flux increases in the direction of flow, while the highest flux ($14.6{\pm}8.40{\mu}g\;N_2O-N/m^2\;hr$) was measured in the slope on the back side of the sand dune. followed by decreases afterward. In contrast, low DOC sediment did not show the geomorphological variations. We found that even though topographic variation influenced $N_2O$ flux and chemical properties, this effect is highly constrained by carbon availability.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.6
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• pp.954-961
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• 2010

Ground-based remote sensing can be used as one of the non-destructive, fast, and real-time diagnostic tools for quantifying yield, biomass, and nitrogen (N) stress during growing season. This study was conducted to assess biomass and nitrogen (N) status of paddy rice (Oryza sativa L.) plants under N stress using passive and active ground-based remote sensors. Nitrogen application rates were 0, 70, 100, and 130 kg N $ha^{-1}$. At each growth stage, reflectance indices measured with active sensor showed higher correlation with DW, N uptake and N concentration than those with the passive sensor. NIR/Red and NIR/Amber indices measured with Crop Circle active sensors generally had a better correlation with dry weight (DW), N uptake and N content than vegetation indices from Crop Circle passive sensor and NDVIs from active sensors. Especially NIR/Red and NIR/amber ratios at the panicle initiation stage were most closely correlated with DW, N content, and N uptake. Rice grain yield, DW, N content and N uptake at harvest were highly positively correlated with canopy reflectance indices measured with active sensors at all sampling dates. N application rate explains about 91~92% of the variability in the SI calculated from NIR/Red or NIR/Amber indices measured with Crop Circle active sensors on 12 July. Therefore, the in-season sufficiency index (SI) by NIR/Red or NIR/Amber index from Crop Circle active sensors can be used for determination of N application rate.

• Journal of the Korea Organic Resources Recycling Association
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• v.19 no.4
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• pp.97-105
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• 2011

A wide diversity of liquid fertilizers and composts produced from the livestock manure in Korea is commonly applied to agricultural lands as an alternative of chemical fertilizers. However, their effects on the crop production and environmental impacts are still vague. The current study was investigated the property changes of paddy soils in sandy loam and silty loam treated with 1) control (no treatment), 2) chemicals, 3) storage liquid fertilizer and 4) SCB liquid fertilizer located in Gyeong-gi province, Korea. The chemical properties of soils in sandy loam and silty loam before the treatment were similar with the ones in the average paddy fields in Korea. Contrary to this, the amount of available phosphorus in sandy loam was higher than the one in the average paddy fields. The number of living organisms in sandy loam and silty loam treated with storage liquid fertilizer and SCB liquid fertilizer were higher than the ones in sandy loam and silty loam with no-treatment and chemicals. Significant difference (P<0.05) among the treatments and no-treatment was observed in sandy loam rather than in silty loam. The amounts of heavy metals were the highest in both sandy loam and silty loam treated with storage liquid fertilizer and SCB liquid fertilizer. The comparison of heavy metals showed that the ones in silty loam were little bit higher than sandy loam. The leaf lengths and dry weights of rices were increased over time, however, no significant difference was observed among each treament. In addition, the rice yield in sandy loam treated with SCB liquid fertilizer was higher than the ones in sandy loam. The highest rice yield was obtained from sandy loam treated with chemicals, but there was no significant difference between storage liquid fertilizer and SCB liquid fertilizer. While the rate of nutrient absorption by rices was the highest in sandy loam and silty loam treated with chemicals, there was no significant difference in sandy loam and silty loam treated with livestock liquid manure.

• Korean Journal of Environmental Agriculture
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• v.37 no.4
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• pp.260-267
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• 2018

BACKGROUND: In this study, shoots of Aralia elata and Kalopanax pictus which belong to the Araliaceae family were analyzed using UPLC-DAD-ESI(+)-QToF/MS to characterize of individual phenolic acids. METHODS AND RESULTS: Total thirteen phenolic acids were identified, and nine hydroxycinnamic acid derivatives have been identified for the first time in shoots of Aralia elata and Kalopanax pictus. For total phenolic acid content (mg/100g dry weight), shoots of Aralia elata and Kalopanax pictus showed 754.8 and 845.3 mg/100g, respectively. 5-O-Caffeoylquinic acid (49%) and 3,5-di-O-caffeoylquinic acid (44%) were found as major phenolic acids in Aralia elata, while 5-O-caffeoylquinic acid (91%) was a major component in Kalopanax pictus. CONCLUSION: On comparing the two plants, it was considered that the biosynthesis of 3,5-di-O-caffeoylquinic acid can be affected by 5-O-caffeoylquinic acid in Aralia elata.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.67 no.2
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• pp.111-120
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• 2022

Improving flour quality is one of the major targets of wheat breeding programs. This study determined the optimum high-molecular-weight glutenin subunits (HMW-GS) to improve flour quality, and analyzed the correlation between agronomic and quality traits in Korea. A total of 180 wheat varieties, including 55 Korean and 125 foreign cultivars, carrying various Glu-1 alleles, were evaluated for their quality and agronomic traits. Results indicated that Glu-A1b, Glu-B1b, and Glu-D1f were the most prevailing alleles for each Glu-1 locus for Korean wheat cultivars. Korean wheat cultivars recorded shorter days to heading (DTH) and longer days to maturity (DTM) compared to foreign cultivars. In addition, an interaction effect was found between Glu-A1 and Glu-B1 alleles on several quality parameters. The combination of Glu-A1c and Glu-B1i showed a higher protein content, dry gluten content, and higher sodium dodecyl sulfate (SDS) sedimentation value than other Glu-A1×Glu-B1 combinations. Cultivars carrying Glu-A1a or Glu-A1b, Glu-B1i or Glu-B1al, and Glu-D1d for each Glu-1 locus exhibited a longer mixing time and stronger mixing tolerance. The DTM positively correlated with the protein content, gluten index and SDS sedimentation value. However, a negative correlation was observed between DTH and quality traits. Owing to the above results, this study suggests that an increase in the frequency of Glu-B1i or Glu-B1al, Glu-D1d coupled with a short DTH and long DTM could significantly improve wheat quality properties.

• Journal of Korea Port Economic Association
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• v.37 no.4
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• pp.161-173
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• 2021

The shipping industry plummeted and was depressed due to the global economic crisis caused by the bankruptcy of Lehman Brothers in the US in 2008. In 2020, the shipping market also suffered from a collapse in the unstable global economic situation due to the COVID-19 pandemic, but unexpectedly, it changed to an upward trend from the end of 2020, and in 2021, it exceeded the market of the boom period of 2008. According to the Clarksons report published in May 2021, the decrease in cargo volume due to the COVID-19 pandemic in 2020 has returned to the pre-corona level by the end of 2020, and the tramper bulk carrier capacity of 103~104% of the Panamax has been in the ports due to congestion. Earnings across the bulker segments have risen to ten-year highs in recent months. In this study, as factors affecting BDI, the capacity and congestion ratio of Cape and Panamax ships on the supply side, iron ore and coal seaborne tonnge on the demand side and Granger causality test, IRF(Impulse Response Function) and FEVD(Forecast Error Variance Decomposition) were performed using VAR model to analyze the impact on BDI by congestion caused by strengthen quarantine at the port due to the COVID-19 pandemic and the loading and discharging operation delay due to the infection of the stevedore, etc and to predict the shipping market after the pandemic. As a result of the Granger causality test of variables and BDI using time series data from January 2016 to July 2021, causality was found in the Fleet and Congestion variables, and as a result of the Impulse Response Function, Congestion variable was found to have significant at both upper and lower limit of the confidence interval. As a result of the Forecast Error Variance Decomposition, Congestion variable showed an explanatory power upto 25% for the change in BDI. If the congestion in ports decreases after With Corona, it is expected that there is down-risk in the shipping market. The COVID-19 pandemic occurred not from economic factors but from an ecological factor by the pandemic is different from the past economic crisis. It is necessary to analyze from a different point of view than the past economic crisis. This study has meaningful to analyze the causality and explanatory power of Congestion factor by pandemic.