• KOREAN JOURNAL OF CROP SCIENCE
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• v.35 no.6
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• pp.481-486
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• 1990

A survey was carried out on the cold-induced sterility of paddy rice in 1988 in the alpine area of Kangweon province when cold spell occurred during late July to early August, During this period minimum temperature as low as 8.5$^{\circ}C$ and 5.7$^{\circ}C$ was recorded at Dunnae and Jinbu, respectively. The rice cultivars, which encountered this cold spe]J at meiotic stage of microspore, were damaged by sterility in most alpine areas of higher than 300m in altitude. To secure spilkelet fertility higher than 80% it was estimated that the minimum and average air temperature accumulated during 13 days of meiotic stage should be higher than 2$25^{\circ}C$ and 285$^{\circ}C$, respectively and/or the duration of lower than 17$^{\circ}C$ in minimum temperature should not exceed fivedays during that period.

• Korean Journal of Agricultural and Forest Meteorology
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• v.8 no.4
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• pp.229-241
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• 2006

Global air temperature has risen by $0.6^{\circ}C$ over the last one hundred years due to increased atmospheric greenhouse gases. Moreover, this global warming trend is projected to continue in the future. This study was carried out to evaluate spatial variations in rice production areas by simulating rice-growth and development with projected high resolution climate data in Korea far 2011-2100, which was geospatially interpolated from the 25 km gridded data based on the IPCC SRES A2 emission scenario. Satellite remote sensing data were used to pinpoint the rice-growing areas, and corresponding climate data were aggregated to represent the official 'crop reporting county'. For the simulation experiment, we used a CERES-Rice model modified by introducing two equations to calculate the leaf appearance rate based on the effective temperature and existing leaf number and the final number of leaves based on day-length in the photoperiod sensitive phase of rice. We tested the performance of this model using data-sets obtained from transplanting dates and nitrogen fertilization rates experiments over three years (2002 to 2004). The simulation results showed a good performance of this model in heading date prediction [$R^2$=0.9586 for early (Odaebyeo), $R^2$=0.9681 for medium (Hwasungbyeo), and $R^2$=0.9477 for late (Dongjinbyeo) maturity cultivars]. A modified version of CERES-Rice was used to simulate the growth and development of three Japonica varieties, representing early, medium, and late maturity classes, to project crop status for climatological normal years between 2011 and 2100. In order to compare the temporal changes, three sets of data representing 3 climatological years (2011-2040, 2041-2070, and 2071-2100) were successively used to run the model. Simulated growth and yield data of the three Japonica cultivars under the observed climate for 1971-2000 was set as a reference. Compared with the current normal, heading date was accelerated by 7 days for 2011-2040 and 20 days for 2071-2100. Physiological maturity was accelerated by 15 days for 2011-2040 and 30 days for 2071-2100. Rice yield was in general reduced by 6-25%, 3-26%, and 3-25% per 10a in early, medium, and late maturity classes, respectively. However, mid to late maturing varieties showed an increased yield in northern Gyeonggi Province and in most of Kwangwon Province in 2071-2100.

• Journal of The Korean Society of Grassland and Forage Science
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• v.27 no.2
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• pp.85-92
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• 2007

This study was carried out to select the promising forage crops fer forage production in paddy field of YARI, RDA, Milyang from 1999 to 2001. The species of forage crop used in this experiment were barley(5 varieties), wheat(2), rye(3) and Italian ryegrass(IRG, 3). Stages of heading, milk and yellow ripe of barley were $20{\sim}24$ April, $6{\sim}10$ May and $21{\sim}24$ May, respectively. In milk to yellow ripe stage, dry matter(DM) yield of barley was $7.89{\sim}9.66$ MT per ha, and averaged ADF and NDF contents were $26.9{\sim}33.3%\;and\;53.1{\sim}59.2%$, respectively. Albori and Naehanssalbori were the most promising varieties among the barley. The growth of wheat was a little late compared to that of barley, but it seemed to be crop having higher forage yield and nutritive value. In milk to yellow stage, DM yield of wheat was $9.13{\sim}10.38$ MT per ha, and nutritive value of wheat was very good(ADF $25.9{\sim}31.7%$ and NDF $53.3{\sim}55.8%$). Heading stage of rye was $20{\sim}24$ April, and it seemed to be suitable far harvest at heading to flowering stage because of heavy lodging after flowering. In flowering stage, DM yield of rye was 13.64 MT per ha, and nutritive value of rye was the lowest among 4 species(ADF $33.1{\sim}38.0%$ and NDF $56.4{\sim}65.0%$). Heading stage of early maturing IRG was 2 May and it seemed to be suitable for harvest at flowering stage of middle May in cropping system. In flowering stage, DM yield of early type IRG was 5.51 MT per ha, and averaged ADF and NDF contents were $30.1{\sim}34.7%\;and\;59.7{\sim}60.5%$, respectively. The results demonstrated that the promising forage crops far forage production in paddy field were rye, barley, early maturing IRG and wheat in Yeongnam region. In Southern region, rye harvesting at early May was recommended when considered middle May of rice transplanting period, and barley(Albori and Naehanssalbori) and early maturing IRG harvesting at middle May were recommended when considered late May of rice planting period. And also, wheat with high nutritive value and possibility for harvesting at late May were recommended in case of transplanting period at early June.

• Journal of The Korean Society of Grassland and Forage Science
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• v.24 no.3
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• pp.217-224
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• 2004

This study was carried out to select the promising forage crops for forage production in paddy field of HARI, RDA, Iksan from 1999 to 2001. The species of forage crop used in this experiment were barley(5 varieties), wheat(2), rye(3) and Italian ryegrass(IRG, 3). Stage of heading, milk and yellow ripe of barley were 26 $April{\sim}l$ May, middle May and late May, respectively. In milk to yellow ripe stage, dry matter(DM) yield of barley was $6.64{\sim}10.47$ MT per ha, and averaged ADF and NDF contents were $31.6\%\;and\;62.2\%$ respectively. Albori was the most promising variety among the barley). The growth of wheat was a little late compared to that of barley, but it seemed to be crop having higher forage yield md nutritive value. In milk to yellow stage, DM yield of wheat was $7.51{\sim}11.96$ MT per ha, and nutritive value of wheat was high(ADF $30.6\%$ and NDF $60.1\%$). Heading stage of rye was $25{\sim}27$ April, and it seemed to be suitable to harvest at heading to flowering stage because of heavy lodging after flowering. In flowering stage, DM yield of rye was 17.26 MT per ha, and nutritive value of rye was the lowest among 4 species(ADF $38.6\%$ and NDF $65.5\%$). Heading stage of early maturing IRG was 30 April and it seemed to be suitable for harvest at flowering stage of middle May in cropping system. In flowering stage, DM yield of early type IRG was 10.77 MT per ha, and averaged ADF and NDF contents were $31.6\%\;and\;59.2\%$, respectively. The results demonstrated that the promising forage crops for forage production in paddy field were rye, barley, early maturing IRG and wheat in Honam region. In Southern region, rye harvesting at early May was recommended when considered middle May of rice transplanting period, and barley(Albori) and early maturing IRG harvesting at middle May were recommended when considered late May of rice planting period. And also, wheat with high nutritive value and possibility for harvesting at late May were recommended in case of transplanting period at early June.

• Proceedings of the Korean Society of Crop Science Conference
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• 2004.04a
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• pp.222-223
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• 2004

• KOREAN JOURNAL OF CROP SCIENCE
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• v.57 no.4
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• pp.441-448
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• 2012

This study was carried out to evaluate the productivity of rice cultivation in extremely late season in Korea and to confirm the effects of pot-raising seedling culture in this case by assessing the growth and yield performance of rice cultivars that are well adapted to late culture. Suitable cultivars for extremely late culture should not have premature heading habit when transplanted around late July and also secure appropriate growth duration before heading. Geumobyeo 1 and Manjongbyeo showed small decrease in the emerged leaves in transplanting in late July or early August and heading occurred at the same time relatively without premature heading. At transplanting from late July to early August in extremely late rice cultivation, ripening was relatively good until transplanting on August 5. At transplanting on July 30, accumulated temperature from heading to the first frost was $853^{\circ}C$ and ripening was good enough. However, heading was delayed by low temperature at transplanting on August 10 and ripening was very poor due to low accumulated temperature of below $800^{\circ}C$, causing drastic decrease of rice yield. The rice yield increased in transplanting with pot seedling, especially the effects of pot seedling was higher in Geumobyeo 1, but panicle number was not enough to secure rice yield owing to short growth duration. In order to cultivate rice in extremely late season, we should select adaptive rice cultivars that have suitable growth duration and excellent ripening in low temperature. Here, pot-seedling did a great role to secure early growth and bigger growth amounts.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.47 no.3
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• pp.151-156
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• 2002

The heritability of sink-source characters was estimated by regression coefficient between F$_2$ and F$_{5}$ in two crosses of IR 66738-118-1-2/Gayabyeo and the Ilpumbyeo/YR 15965 Acp 33. In order to get the some basic information for breeding of high yielding rice, genetic resources of new plant type with low tiller and heavy panicle were used. Most of the sink and source characters in Ilpumbyeo/YR 15965 Acp 33 cross showed high heritability over than 0.224. But the specific leaf area and sink-source ratio displayed low heritability being 0.009 and 0.013, respectively. Heritability of all sink and source characters in IR 66738-118-1-2/Gayabyeo cross ranged from 0.115 to 0.247. Correlation coefficient between yield and yield components in both combination were in the ranged between 0.001 and 0.247. But correlations among the yield components were not significant. Correlations between the yield and sink-source characters in both combinations were also highly significant. Particularly, correlation between the grain tiling ratio and most of the sink-source characters in IR 66738-118-1-2/Gayabyeo cross were not significant. In Ilpumbyeo/YR 15965 Acp 33 cross, correlations between grain filling ratio and source characters were positively significant. but sink characters (sink capacity and sink-source ratio, etc) were negatively significant.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.5
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• pp.608-618
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• 1995

This study was conducted to determine physiobiochemical basis of heterosis using rice hybrids such as Shanyou 63 (Zhenshan 97As Minhui 63) and Teyou 63 (Longtepu A Minhui 63) as compared with inbred rice like Milyang 23. Seed protein patterns of rice hybrid showed complementary genetic characteristics inherited from their parents. Hybrid rice had larger embryo and higher $\alpha$-amylase activity than those of inbred rice. The larger embryo of hybrid was significantly correlated with tillering ability and high number of low node tillers jplant increased by 60~70% in Shanyou 63, leading to higher productive tillers/plant which directly influenced on grain yield of hybrid rice. These characters were further supported by high chlorophyll content in hybrids. Exogenous application of GA$_3$ (0.02 ppm) on inbred rice like Milyang 23, increased significantly $\alpha$-amylase activity, but no effect of GA$_3$ on hybrid rice was observed, indicating that sufficient amount of GA$_3$ is endogenously present in hybrid rice, showing 1 to 3.5 fold higher activity of $\alpha$-amylase in hybrid rice, which trigger heterosis from the germinating stage. Further, activity of cytochrome c oxidase was 2.66 to 5.52 fold higher in hybrid rice than that of inbred rice, indicating that rice hybrids have very active metabolism reflecting vigorous growth starting from the germinating stage, in turn leading to higher tillering ability.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.5
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• pp.522-527
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• 1997

To find out the optimum seeding rate in corrugated water seeded rice, field experiment was carried out at Yeongdeog Substation of the National Yeongnam Agricultural Experiment Station for two years, 1994 and 1995. A rice cultivar Donghaebyeo, was seeded on May 15 with five seeding rate from 3kg /10a to 7kg /10a. The number of seedling stand per unit area was curvilinearly increased with seeding rate. In characteristics of rice plant associated with lodging, the plant height, fresh weight per tiller, Culm wall thickness and ratio of gravity center were not significantly different among seeding rates, but the breaking strength of 4th internode was slightly decreased with increasing seeding rate and thus, lodging index was generally greater at higher seeding rate than lower seeding rate. Field lodging was observed at 1~3 degree in seeding rate of 5~7kg /10a. Panicle number per unit area was generally increase with increase of seeding rate, while ratio of ripened grain was decreased with increase of spikelet number. Milled rice yield was curvilinearly increased with seeding rate. The optimum seeding rate in the highest rice yield was 4.8kg /10a in 1994, and 4.3kg /a in 1995, respectively.

• Korean Journal of Weed Science
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• v.32 no.3
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• pp.188-194
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• 2012

Field experiments were conducted to investigate the competition relationships of main paddy weeds with transplanted rice grown in paddy conditions. Data were used to predict crop yield as a function of weed density using a rectangular hyperbola model and determine weed economic threshold (ET) levels. The rectangular hyperbola (equation 2) was fitted to rice yield to estimate weed-free rice yield ($Y_o$) and weed competitivity (${\beta}$). Its competitivity for M. vaginalis was 0.0007445, 0.0005713, 0.000988 and 0.0008846 in Daejeon, Suwon, Iksan and Naju, respectively. The competitivity at harvest represented by parameter ${\beta}$ ranged from 0.001611 in Naju to 0.002437 in Iksan for S. trifolia. The ET levels of main paddy weeds in machine transplanted rice cultivation were well estimated based on the herbicides applied and its application cost. Therefore, our results can be used to support decision-making on herbicide application for weed management in transplanted rice cultivation.