• KOREAN JOURNAL OF CROP SCIENCE
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• v.33 no.1
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• pp.12-22
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• 1988

The effects of pH and Aluminum treatment on the seedling growth were examined with 11 cultivar under three levels of pH in nutri-culture.. Growth and yield responses of soil pH and nitrogen fertilization were also studied with five cultivars under 3 levels of soil pH and 3 levels of nitrogen application in the field experiment. The effect of pH on the seedling growth was not significant, but Aluminum treatment significantly decreased the seedling growth in nutri-culture except Dusan ＃12. Chlorophyll contents of leaves, dry weight of plants, culm length, spike numbers per unit area, grain numbers per spike, grain weight, and yield were decreased as the decrease of soil pH, and thus highly significant correlation between soil pH during barley growth and yield was observed in all cultivars examined. The stable cultivars to different soil pH with high yield was not found although the decreases of yield were different with cultivars. The increase of nitrogen fertilization significantly increased the nitrogen and chlorophyll contents of leaves, and dry weight of plants, while showed a little effects on the culm length, spike number per unit area, grain number per spike, grain weight and yield. The yield was significantly correlated with culm length, dry weight of plants, grain numbers per spike and 1000 grain weight at each pH levels.

• Korean Journal of Materials Research
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• v.28 no.10
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• pp.570-577
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• 2018

This study examines the effect of microstructural factors on the strength and deformability of ferrite-pearlite steels. Six kinds of ferrite-pearlite steel specimens are fabricated with the addition of different amounst of Mn and V and with varying the isothermal transformation temperature. The Mn steel specimen with a highest Mn content has the highest pearlite volume fraction because Mn addition inhibits the formation of ferrite. The V steel specimen with a highest V content has the finest ferrite grain size and lowest pearlite volume fraction because a large amount of ferrite forms in fine austenite grain boundaries that are generated by the pinning effect of many VC precipitates. On the other hand, the room-temperature tensile test results show that the V steel specimen has a longer yield point elongation than other specimens due to the highest ferrite volume fraction. The V specimen has the highest yield strength because of a larger amount of VC precipitates and grain refinement strengthening, while the Mn specimen has the highest tensile strength because the highest pearlite volume fraction largely enhances work hardening. Furthermore, the tensile strength increases with a higher transformation temperature because increasing the precipitate fraction with a higher transformation temperature improves work hardening. The results reveal that an increasing transformation temperature decreases the yield ratio. Meanwhile, the yield ratio decreases with an increasing ferrite grain size because ferrite grain size refinement largely increases the yield strength. However, the uniform elongation shows no significant changes of the microstructural factors.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.32 no.3
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• pp.294-301
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• 1987

This experiment was carried out to investigate the occurrence of tiller and its proportion to grain yield under 5 different plant densities. Plant density 5 x 5cm was more favorable for increasing the number of spikes per unit area, where leads to improve grain yield. Effective tillers showed only main stem, M$_1$-axil and M$_2$-axil, indication more effective tillers in M$_1$ rather than main stem. Every tillers held at least 6 leaves to bear spikes, indicating that main stem has 12 -13 leaves. Leaves attached on main stem M$\sub$0/ and M$_1$ were very important as main source of photosynthesis, especially under more compart plant densities while leaves of M$_1$ occupied 66.8% in a plant. The proportion of grain yield of each tiller to total grain yield per plant was high in main stem under conpact plant density, in M$_1$ stems under less compact plant density, and in M$_2$ -stems under wide plant density, indicating same result on multiple regression analysis.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.238-238
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• 2017

Salt stress is one of the deteriorating abiotic stresses due to the climate change, which causes over-accumulation of $Na^+$ and $Cl^-$ ions in plants and inhibits the growth and yield of rice especially in coastal Southeastern Asia. The yield components of rice plant (panicle number, spikelet number per panicle, 1000-grain weight, % of ripened grains) that are majorly affected by salt stress vary with growth stages at which the plant is subjected to the stress. In addition, the salt sensitivity of each yield component differs among rice varieties even when the salt-affected growth stage was same, which indicates that the physiological mechanism to maintain each yield component is different from each other. Therefore, we hypothesized that rice plant has different genes/QTLs that contribute to the maintenance of each yield component. Using a Japanese leading rice cultivar, Koshihikari, and salt-tolerant Nona bokra's chromosome segment substitution lines (CSSLs) with the genetic background of Koshihikari (44 lines in total) (Takai et al. 2007), we screened higher yielding CSSLs under salinity in comparison to Koshihikari and identified the yield components that were improved by the introgression of chromosome segment(s) of Nona bokra. The experiment was conducted in a salinized paddy field. One-month-old seedlings were transplanted into a paddy field without salinity. These were allowed to establish for one month, and then the field was salinized by introducing saline water to maintain the surface water at 0.4% salinity until harvest. The experiments were done twice in 2015 and 2016. Although all the CSSLs and Koshihikari decreased their yield under salinity, some CSSLs showed relatively higher yield compared with Koshihikari. In Koshihikari, all the yield components except panicle number were decreased by salinity and % of ripened grains was mostly reduced, followed by spikelet number per panicle and 1000-grain weight. When compared with Koshihikari, keeping a higher % of ripened grains under salinity attributed to the significantly greater yield in one CSSL. This indicated that the % of ripened grains is the most sensitive to salt stress among the yield components of Koshihikari and that the Nona bokra chromosome segments that maintained it contributed to increased yield under salt stress. In addition, growth analyses showed that maintaining relative growth rate in the late grain filling stage led to the increased yield under salt stress but not in earlier stages.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.101-101
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• 2017

This study was carried out to improve yield potential of Tongil type rice variety based on QTLs analysis associated with yield component using a total of 386 rice recombinant inbred lines (RILs) derived from a cross between Tongil type high yield variety "Hanareum2" and Japonica variety "Unkwang". 384 SNP markers were used, and 241 of them (62.6%) were polymorphic between Hanareum2 and Unkwang. One hundred forty-four QTLs in 11 traits, such as heading days, were detected. Most of them were 21 QTLs associated with 1000 grain weight and the least was 8 QTLs associated with panicle number. The QTL, qDTH3-2 associated with days to heading was identified to delay heading date for 2.4~2.6 day. Eleven QTLs were associated with culm length. The QTL, qCL1-2 on chromosome 1, was identified to decrease culm length. A total of 16 QTLs were detected for panicle length. Three QTLs, qPL3, qPL6, and qPL7-1 were increased panicle length. Seven QTLs related to panicle number except qPN7 were increased the number of panicle. Four QTLs related to grain number per panicle, qGNP2-1, qGNP6, and qGNP7, were increased the number of grains. Three QTLs associated with grain filling rate, qGFR1, qGFR2-2, and qGFR7-1 were increased grain filling rate. Twelve QTLs associated with 1,000 grain weight. were increased the grain weight. Fourteen QTLs were identified associated with grain length. 10 QTLs, such as qGL1-1, were increasing grain. Fifteen QTLs associated with grain width were detected. The 8 QTLs, such as qGW1-1, were elongated grain width. Seventeen QTLs were associated with grain thickness, and ten QTLs of them were increased grain thickness. We need further study to develop introgression lines of each QTL to improve yield potential of Tongil type rice variety.

• Korean Journal of Agricultural Science
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• v.16 no.2
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• pp.138-151
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• 1989

In order to find the effects of seed size on the early seedling growth and yield of soybean, three soybean cultivars in Korea were investigated. Seed size was classified into large and small according to the weight and planted in pots(1/5000a) and in the field. Three soybean cultivars respresenting large, medium and small grains were Hwangkeum-kong, Kwangkyo and Bangsa-kong respectively. These cultivars were planted on June 20, 1987. 1. The plant height, stem diameter, root length and leaf area index(LAI) of the seed with large size seemed larger than the seed with small size regardless of cultivars. 2. The fresh and dry weight were different depending upon the grain sizes. The large grain had heavier fresh and dry weight than the small grains. 3. The protein consumption rate of the cotyledon of Bangsa-kong with small grain size was faster than the Hwangkeum-kong with large grain size. 4. The stem length, stem diameter and number of main stem node of the seed with large size seemed larger than the seed with small size. Large grains of Hwangkeum-kong were the highest in the number of branch node and number of node. 5. The number of pods and grains per plant of Bangsa-kong with small grain size was larger than the Kwangkyo with large grain size. 6. The yield per 10a for Hwangkeum-kong, Hwangkyo and Bangsa-kong were 226.3kg, 193.0kg and 192.8kg, respectively and they were all statistically different. The yield increases of large grains over small grains in the Hwangkeum-kong, Kwangkyo, and Bangsa-kong were 7.4%, 8.0% and 9.2%, respectively.

• Korean Journal of Materials Research
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• v.26 no.6
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• pp.325-331
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• 2016

This paper presents a study of the tensile properties of austenitic high-manganese steel specimens with different grain sizes. Although the stacking fault energy, calculated using a modified thermodynamic model, slightly decreased with increasing grain size, it was found to vary in a range of $23.4mJ/m^2$ to $27.1mJ/m^2$. Room-temperature tensile test results indicated that the yield and tensile strengths increased; the ductility also improved as the grain size decreased. The increase in the yield and tensile strengths was primarily attributed to the occurrence of mechanical twinning, as well as to the grain refinement effect. On the other hand, the improvement of the ductility is because the formation of deformation-induced martensite is suppressed in the high-manganese steel specimen with small grain size during tensile testing. The deformation-induced martensite transformation resulting from the increased grain size can be explained by the decrease in stacking fault energy or in shear stress required to generate deformation-induced martensite transformation.

• Research in Plant Disease
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• v.19 no.3
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• pp.196-200
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• 2013

This study was carried out to investigate yield loss due to soybean leaf spot disease caused by Cercospora sojina Hara and to determine the economic threshold level. The investigations revealed highly significant correlations between disease severity (diseased leaf area) and yield components (pod number per plant, total grain number per plant, total grain weight per plant, percent of ripened grain, weight of hundred seed, and yield). The correlation coefficients between leaf spot severity and each component were -0.90, -0.90, -0.92, -0.99, -0.90 and -0.94, respectively. The yield was inversely proportional to the diseased leaf area increased. The regression equation, yield prediction model, between disease severity (x) and yield (y) was obtained as y = -3.7213x + 354.99 ($R^2$ = 0.9047). Based on the yield prediction model, economic injury level and economic threshold level could be set as 3.3% and 2.6% of diseased leaf area of soybean.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.45 no.4
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• pp.237-240
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• 2000

This experiment was conducted to evaluate the effect of split application of nitrogen(N) on development of vascular bundle(VB) and yield components of rice. Two cultivars were used in this study; IR58, an indica type and Shinunbongbyeim a japonica type. The number and total cross sectional area of the VB in the peduncle and leaf blade were more and bigger in N split application than 100 percent basal fertilizer. Nitrogen split application at necknode differentiation stage increased the number and size of the VB. Nitrogen split application resulted in increased panicle number with application of N before transplanting and at tillering stage; increased spikelets number with N application at necknode differentiation stage; and increased spikelet fertility and 1000 grain weight with N application at necknode differentiation and heading stages. Grain yield increased 7-10% in N split as compared to all basal application. The total cross sectional area of VB in peduncle closely correlated with the number of spikelets per panicle. Nitrogen management can have an impact on spikelet differentiation through more and bigger VB and increase grain yield potential.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.58 no.1
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• pp.78-83
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• 2013

The excessive and indiscriminate use of chemical fertilizers in the past has brought serious soil and other environmental problems so alternatives over this agrochemical are being searched. Our study focuses on the effects of expanded rice hull inoculated with selected beneficial microorganisms on growth (through agronomic characters), yield and yield components, and grain quality indices of rice. Results showed that favorable effects of different expanded rice hull preparations were not readily apparent at vegetative stage and only treatments with supplemental chemical fertilizer application were comparable with the conventional practice. Expanded rice hull combined with 50% rate of chemical fertilizer exhibited a significantly higher yield (6,471 kg $ha^{-1}$) over conventional practice (5,719 kg $ha^{-1}$). Good milling quality indices were observed in treatments having 50% chemical fertilizers plus alternatives from expanded rice hull. Finally, we demonstrated that chemical fertilizer rate can potentially be reduced into 50% if combined with expanded rice hull, and show even better output than chemical fertilizer alone.