• Journal of The Korean Society of Grassland and Forage Science
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• v.10 no.1
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• pp.42-47
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• 1990

Silage productivity of 7 corn and 3 sorghum hybrids was determined at two planting dates differing in rice black-streaked dwarf virus (RBSDV) infection rates in the southern part of Korea where RBSDV is prevalent. 1. Percent stand was similar between two planting dates, but that of corn hybrids (85.0-99.5 %) was higher compared with sorghum (59.8-82.3 %). Culm length of corn hybrids at April 23 planting was longer compared with May 20 planting, but that of sorghum hybrids was similar between two planting dates. 2. RBSDV infection rate of corn hybrids at April 23 planting was lower compared with May 20 planting, but sorghum was not infected at both planting dates. Among corn hybrids Suweon 19 was most severely infected, but Suweon 99 was least infected at both planting dates. 3. Percent ear bearing plants and earltotal dry matter (TDM) ratio of corn hybrids at April 23 planting was higher than those of May 20 planting. Among the corn hygrids percent ear beraring plants, ear/TDM ratio of Suweon 19 was lowest at both planting dates due to severe RBSDV infection. Ear/TDM ratio of sorghum hybrids was below 17.8 % due to sterility and partially bud damages. 4. Silage yield at April 23 planting was higher than that at May 20 planting and sorghum hybrids outyielded corn hybrids. Silage yield of Suweon 19 and Jinjuok was lowest due to severe RBSDV infection. 5. Crude protein was similar regardless planting dates, species, and varieties except the lowest P 931. Ether extract at April 23 planting was lower then that at May 20 and corn was lower compared with sorghum hybrids. Crude fiber and nitrogen free extracts(NFE) was similar between planting dates. Crude fiber of corn was lower, but NEF was higher compared with sorghum, but similar among hybrids in a species. 6. In vitro dry matter digestibility (IVDMD) at May 20 planting was higher than that of April 23 planting and corn was higher than sorghum hybrids. Digestible dry matter (DDM) of both corn and sorghum at April 23 planting was higher than that of May 20 planting. At April 23 planting DDM of all corn and sorghum hybrids was similar, but DDM of Suweon 19 and Jinjuok was lower than other corn and sorghum hybrids.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.24 no.3
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• pp.59-65
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• 1979

Severe outbreak of necrotic. soybean mosaic virus. (SMV -N) strain has been observed on soybean (Glycine max) in the central northern pans of Korea. Thirty soybean cultivars developed from Korea. Japan, and USA were tested for the estimation of infection percentages and ratings at 4 different planting dates. SMV-N infection was decreased by delaying the planting dates, but no differences were observed in conmon mosaic virus. Most of the soybean cultivars developed in Korea, and Japan were more susceptible to SMV- N than the US developed cultivars. Infection ratings of SMV-N showed highly significant negative correlations with common SMV regardless of planting dates.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.63 no.3
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• pp.210-218
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• 2018

This study was conducted to examine the influence of different transplanting dates on rice quality and starch properties (morphology and pasting properties) of rice varieties that may be used for the production of rice flour. Three rice flour varieties, 'Seolgaeng', 'Hangaru', and 'Milyang317', were transplanted on May 20, May 30, June 10, and June 20. The peak viscosity decreased with a delay in the transplanting date. However, the amylose content increased with a delay in the transplanting date, whereas that of protein decreased. Amylopectin short-branch chain content increased in the rice varieties that were transplanted on May 30. The morphology of the starch granule of the varieties was determined by SEM. No apparent external difference in the starch granules was observed for the different transplanting dates. These results indicate that the transplanting date influenced the amylopectin structure and pasting properties, which led to changes in the physicochemical characteristics of rice starch.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.32 no.4
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• pp.425-430
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• 1987

The present experiment was carried out to investigate the effects of direct sowing time and transplanting culture of Sculellaria baicalensis GEORGE on the grows, the yield and it's components. The results obtained are summarized as fallows; The number of days from seeding to emergence was recognized lineary negative correlation between seeding dates and transplanting dates. Plant height was longest on Apr. 15 Seeding and Apr. 1 transplanting, and was short in the early seeding and transplanting, and the late seeding and transplanting. Stem diameter was thickest on Apr. 15 seeding and Apr. 1 transplanting, and was thin in the early, and the late seeding and trasplanting. Length and dry weight of root were increased on Apr. 15 seeding. In the transplanting date, Length and dry weight of root were increased on Apr.1. Yield of dry root was highest in Apr. 15 seeding date. In the transplanting culture, yield of dry root was highest in Apr.1.

• Asia-Pacific Journal of Business
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• v.8 no.2
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• pp.1-14
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• 2017

Initial public offering (IPO) has been well known to be underpriced initially and under-performed in the long run. However, whether an IPO is underpriced or not strongly depends on how to measure the fair value. This paper hand collects data of IPOs newly listed in Korea market when whether IPO is overpriced or not is clearly distinguishable. The overpriced IPO refers to as the one the underwriters buy back after the listing. With the data, the paper examines that IPOs are overpriced and that the characteristics are related to the underpricing at the aftermarket dates and the performance in the long run. The data of clearly overpriced IPOs are little available from other IPO markets like US IPO market. From the data of IPOs listed under the underwriting rule of market stabilization, the results obtainable are the followings. First of all, the average initial return 70% of the underpriced IPO at the aftermarket dates is greater than the one 40% of the overpriced one. The overpriced IPOs are priced highly over the mid prices of the price bands at the pricing dates and then supported by relatively higher subscription rates of individual investors. The probit analyses moreover report that individual investors do not distinguish the overpricing of IPOs from the underpricing. These imply that the overpricing is strongly affected by the underwriting rule on the initial pricing.

• Journal of Ecology and Environment
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• v.46 no.3
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• pp.190-201
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• 2022

Background: The introduction of new living modified (LM) crops may pose a latent threat to the biodiversity of each country. Here, we used sunflowers (Helianthus annuus L.) as a study system to investigate the potential for invasiveness of LM crops under different environmental conditions when released into a natural ecosystem in South Korea. We examined the seed germination, survival, and flowering of sunflowers under competition with wild plants at different sowing dates (March-December) and plot sizes (1 m × 1 m and 2 m × 2 m). Results: The germination rate showed a significant difference according to the sowing date. In addition, several sunflowers survived in plots with a high germination rate, which also led to a higher flowering rate. We found that the smaller the plot, the smaller the area available for inter-species competition, and the higher the number of surviving sunflower plants. The relative dominance and importance value of the species varied significantly between the sowing dates; in particular, sunflowers sown in March could compete with wild plants for longer than those sown on other sowing dates. Conclusions: These observations indicate that the potential for invasiveness of sunflowers differs depending on the environmental conditions and seed density at the time of release.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.30 no.3
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• pp.340-346
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• 1985

Field experiments were carried out to investigate the effects of sowing dates, ferrilizer levels and clipping treatment of forage production and quality of barley and rye in paddy field. The field emergence rates in barley varieties was decreased rapidly at sowing after November. But in rye varieties, it was not decreased even in sowing until Nov. 3. Winter survival of barley and rye varieties were not affected by fertilizer levels. And winter survival decreased with delay in sowing dates in barley varieties, but, it was not influenced by sowing dates in rye varieties. The production of forage dry matter at heading stage was increased with fertilizer levels, and was decreased with delay in sowing dates. Content of crude protein and crude fat of dry forage at heading stage were increased with fertilizer levels. But, content of crude ash, crude fiber and TDN were not influenced by fertilizer levels. As increased fertilizer levels, NFE Content was decreased and TDN yield was increased with fertilizer levels. In comparisons of TDN yield between barley and rye varieties, TDN yield of rye were superior to those of barley. Clipping twice produced more forage yield than clipping once in both crops. However, optimum clipping interval was about 40 days between first and second clipping in rye but not determined in barley. The l2cm clipping height was the highest production in average total yield.

• Journal of The Korean Society of Grassland and Forage Science
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• v.22 no.4
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• pp.241-246
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• 2002

Rye-hairy vetch mixture would be recommended fur produce higher yield and conserving soil environment. This experiment was conducted to investigate the effect of planting and harvest dates on quality and productivity of rye-hairy vetch mixture. Plant height of rye and hairy vetch was increased with delayed harvest dates, but it found that there was on significant difference among seeding dates. The dry matter(DM) content was increased with delayed harvest dates, and it showed 30% DM in mid-May. Crude protein(CP) content was decreased sharply from 17~18% in heading stage to 9~10% in flowering stage. The content of ADF(Acid detergent fiber) and NDF(Neutral detergent fiber) were increased with delayed harvest date, but IVDMD(In vitro dry matter digestibility) and TDN(Total digestible nutrient) were decreased. The change of dry matter yield was affected significantly by harvest date but was not by seeding time. The results of this experiments indicated that harvest in late-April would be recommended to produce the highest yield and quality if it is considered to cultivate com fur silage. Harvest in mid-May would be recommendable with the cultivation of early maturity silage corn or sorghum $\times$ sudangrass hybrids.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.3
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• pp.236-242
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• 1999

To examine the seedling stand and growth as affected by early seeding dates of dry direct seeded rice in the Honam plain area of Korea, Dongjinbyeo was seeded at six seeding dates from early March to late April in rice fields of silty loam soil(Jeonbuk series) at the National Honam Agricultural Experiment Station (NHAES) for two years, 1996 and 1998. Seedling stand decreased slightly. with an early seeding date, but it produced more than the optimum seedling number except for the seeding of 25 March in 1996. Days to emergence was significantly longer, as seeding date was earlier, and days to emergence by early seeding was shortened only by 8 days because the mean air temperature was lower in 1996 than average, while in 1998, the reduction effect was nine to twenty five days because the mean air temperature was higher than average. In early seeding, various weeds occurred at the emergence date of rice and dominant weeds were Alopecurus aequailis, Ludwigia prostata and Rorippa islandica. NH$_4$$^{+}$ -N content in the soil at the 5th leaf stage and maximum tillering stage were lower, as the seeding date was earlier when nitrogen was split applied as basal and top dressed in 1996, while it was not significantly different among seeding dates when nitrogen was intensively applied as a top dressing in 1998. Tiller number at the maximum tillering stage and panicle number/m$^2$ were more, as seeding date was earlier in 1996, while it was not different in 1998. Filled grain rate and 1,000 grain weight was not different among the seeding dates. Milled rice yield was significantly decreased in the seeding before the middle of March, but in the seeding after late March, it was not varied when compared with the normal seeding date in 1996, while in 1998, there was no difference among seeding dates. From the above results, in consideration of seedling stand, weed occurance, rice growth and milled rice yield, the critical optimum early seeding time in the southern plain area may lie in early April. But it was suggested that when soil moisture is proper for seeding practices, seeding amount is increased and nitrogen is applied after plumule emergence of rice, milled rice yield may not be reduced in the seeding of middle or late March, compared with the seeding in April.l.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.31 no.4
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• pp.470-476
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• 1986

In order to find out the optimum seeding date of Job's tears, this study was investigated ecological characters, yield components and yield of Jang Seong native variety at 6 seeding dates (March 20, March 30, April 10, April 20, April 30 and May 10). Emergence period and heading period were shortened as the seeding date was late, and the number of leaves on the main stem was increased as the seeding date was early. Maturing period was 63-66 days when we seeded in March 20, March 30, April 10 and April 20, and it was delayed 68-77 days when we seeded on April 3$^{\circ}$ and May 10. Culm length was longest in April 10 seeding (it was 186.6 cm), and it grew short in the early and the late seeding, but there was no significant difference among seeding dates. Stem diameter was thickest in April 10, and April 20 seeding, that is, thickened to 10.1 mm, and it was thin in the early and the late seeding. Productive tiller number per hill was increased most in April 10 and April 20 seeding, that is, increased to 6.2, and it was decreased in the early and the late seeding. 100 grain weight was heaviest in April 10 seeding; it was 10.7 g, and it was light in the early and the late seeding. Ripeness rate was highest in April 10 seeding (87.4%), and it was lowest in May 10 seeding (76.3%). Grain yield was highest in April 10 seeding (602.8kg per l0a); therefore this period is regarded as optimum seeding date. C. protein, C. fat, C. fiber and C. starch showed significant difference among seeding dates, and C. protein showed possitive correlation (r =0.9811 **) and C. fiber Negative collelation (r =-0.8937*) with seeding dates.