• Korean journal of applied entomology
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• v.9 no.2
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• pp.91-94
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• 1970

Tobacco wild fire caused by Pseudomonas tabaci(Wolf et Foster) Stevens is one of the most important diseases on tobacco plant in Korea. The objectives of the study were to investigate: 1) the relationships between environmental conditions and the disease development, 2) the effect of chemical spray and soil sterilization on the disease development, and 3) the proper date for chemical sprays during the growing season. The appearance of wild fire on tobacco plant was somewhat proportional to temperature and moisture in atmosphere. The first occurrence of the disease was in late part of June when the temperature was $18\;to\;20^{\circ}C$. with $65\;to\;70^{\circ}C$ of relative humidity. The disease was, then, gradually increased during early part of July with the temperature of $22\;to\;26^{\circ}C$. and $85\;to\;86^{\circ}C$ of. relative humidity. The rapid development of the disease occurred after heavy rain or storm during July. Two to three times of Phytomycin sprays(1:300-350) during the epidemic season reduced $28.3\%$ of disease damage when compared with control plot. Soil sterilization with chloropicrin. 10 liter/10a, Prior to transplanting of seedlings reduced not only wild fro damage but also the other tobacco diseases on field. The study showed that the damage caused by tobacco wild fro could be reduced with the use of early varieties and/or 2 or 3 times of Phytomycin sprays during early part of June, and soil sterilization with chloropicrin prior to transplanting.

• Korean Journal of Organic Agriculture
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• v.18 no.1
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• pp.75-82
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• 2010

The purpose of this study is to investigate an occurrence rate of rice stripe virus disease under different rice transplanting time and different rice cultivars. After final harvest, the yield of rice infected by rice stripe virus was obtained on Wangchal cultivar compared to uninfected rice. The results obtained as following: 1) Yield of rice infected by rice stripe virus was decreased by 64% with reduction of culm length, pancile length, number of spike, number of spikelet, and grain filling compared to uninfected rice, 2) An occurrence rate of rice stripe virus disease under different rice planting season was high as order of May 30 > June 15 > July 1. In additional, to reduce a rice stripe virus disease on higher disease occurrence region and susceptible cultivars, rice planting season will be accepted on and after June 15, and 3) Eighteen cultivars were resistance cultivars such as Hwayeongbyeo, Onnuri, Ilmibyeo, Nampyongbyeo, Dongjin2ho, Hopumbyeo, Hwangkeumnuri, Malgeumi, Saenuri, Pungmi1ho, Haechanmulgyeo, Hwangkeumnodeul, Chilbobyeo, Dongjinbyeo, Younganbyeo, Junambyeo, Samkwangbyeo, and Nakdongbyeo. Twenty-one cultivars were susceptible cultivars such as Odaebyeo, Unkwangbyeo, Shinungbong1ho, Manabyeo, Hopyongbyeo, Borami, Damibyeo, Hwangchalbyeo, Sulgengbyeo, Nongrim6ho, Sasanishigi, Yunishigari, Chungmubyeo, Dongjin1ho, Huknambyeo, Guromy, Shanghehanghulna, Heukchalbyeo, Heukhwangbyeo, and Aranghwangchalbyeo.

• Journal of The Korean Society of Grassland and Forage Science
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• v.34 no.4
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• pp.227-233
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• 2014

This experiment was undertaken to develop triple cropping systems for winter cereal crops for forage, early maturing rice and oats, and to select a winter forage crop in order to determine rice transplanting time at paddy fields in the southern region. Also, the productivity and feed value of the resulting forage crops were examined. When winter cereal crops used for forages are first harvested at the early maturing rice transplanting period, and again harvested during the winter forage crop harvesting period, the fresh yield and dry matter yield of rye were 32.0, 42.3 ton/ha and 5.8, 16.5 ton/ha, respectively, demonstrating higher yields than other winter crops. The early maturing rice, 'Jopyeong', transplanted on June 4 had a lower percentage of ripened grain compared to those transplanted on May 6, and milled rice yield transplanted on June 4 was also decreased by 22%. Thus, the results showed that early transplanting was profitable. Regarding the oats grown during the fall cropping season, the heading date for the oats sown first was on October 10, but the heading was not observed in those sown later. Dry matter yield and TDN yield of the second sowing was less than 50% compared to the first. Consequently, rye may be the most suitable winter forage crop for triple cropping systems. Early transplanting of 'Jopyeong' after rye harvesting before April 30 in addition to timely sowing of oats in the fall season would be profitable for rice and forage production using triple cropping systems in the southern region.

• Korean Journal of Soil Science and Fertilizer
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• v.36 no.1
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• pp.24-31
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• 2003

Objective of this study was to assess rice growth and percolation water salinity under the irrigation of the discharge waters from the municipal wastewater treatment plant and from the industrial wastewater treatment plant as alternative water resources during transplanting season. Three kinds of waters were irrigated; the discharge water from an industrial wastewater treatment plant (DIWT), the discharge water from the municipal wastewater treatment plant (DMWT), and groundwater. Concentrations of $COD_{er}$, $NH_4{^+}_-N$, $Mn^{2+}$, and $Ni^+$ in DIWT, SS content and $PO_4-P$ concentrations in DMWT were higher than those of reuse water criteria of other country for agricultural irrigation. The plant height in the irrigation of DMWT was shorter by 2 cm than the groundwater irrigation except for 10 days irrigation. However, the number of tillerings was not significantly different between DMWT and the groundwater. For the harvest index, there were no significant difference between DMWT and DIWT for 20 days irrigation, but slightly higher in DIWT than that of DMWT for 30 days irrigation regardless of soil types. The salinity of percolation water in the rhizosphere with irrigation of DIWT had more twofold than DMWT, but SAR value from DMWT had no significantly different from the groundwater irrigation. The average $EC_i$ values in the rooting zone irrigated with DIWT and DMWT for 30 days after rice transplanting were 4.7 and $3.4dS\;m^{-1}$ in clay loam soil, and were 3.5 and $2.5dS\;m^{-1}$ in sandy loam soil, respectively. There was dramatic decrease in $EC_i$ value at 30 days after rice transplanting even though $EC_i$ of DIWT had more twofold than DMWT. However, $EC_i$ from DMWT had no significant difference from the groundwater. Therefore, it might be considered that there was limited possibility to irrigate DMWT to overcome drought injury of rice transplanting season in paddy field.

• Research in Plant Disease
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• v.6 no.1
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• pp.23-26
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• 2000

Effects of infection time of the clubroot pathogen, Plasmodiophora brassicae, on yield loss of Spring-sown Chinese cabbage plants were examined in field experiments. Yield loss of Chinese cabbage plants increased as the infection time becomes early. Plants infected at 20 days after transplanting or earlier were completely killed before harvest, and those infected at 30 days after transplanting were healthy in appearance but their head weights were reduced to 59% with poor commodity value. The plants infected 40 days after transplanting were not affected in yield. Development of root hairs in diseased plants was greatly reduced as the infection progressed, and root length was reduced to 1/2 to 1/3 of that of healthy plants. root galls were first developed 20 days after inoculation and rapidly enlarged to reach the peak in size 20 days from initial development, and decayed thereafter. Development and decay of root galls tended to be faster at later season as air temperature became high, regardless of the infection time. Diseased plants started to wilt approximately 10 days after root gall development. Root galls began to decay 10 days after initial plant wilting, and then were completely rotten within following 10 days. Based on the results, root gall development stages on spring-sown Chinese cabbage plants could be grouped into 20 days of root gall enlargement period, and 10 days of root gall decay period, followed by survival period in soil.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.183-183
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• 2017

In the early part of rice growth, root volume primarily limits the amount of plant-accessible nitrogen (N). Therefore, knowledge of the root development is important for modeling N uptake of rice. The timing when the volume of rhizosphere cover the whole soil is also important to carry out timely top dressing. However, information about initial root expansion and associated N uptake is limited due to intrinsic technical difficulties in assessing below-ground processes. Some studies, however, showed a close relationship between below-ground root and above-ground leaf development, suggesting a possibility that above-ground attributes could serve as surrogates for the root processes. In this study, we investigated the relationship between below-ground and above-ground development of rice. Field experiments were conducted where we cultivated Koshihikari (a leading cultivar in Japan) for four different cropping schedules in 2012. In 2016, Gimbozu (HEG4) and three flowering time mutant lines of Gimbozu (X61 (se13), HS276 (ef7), DMG9 (se13, ef7)) were examined for a single season. Experiments were performed with three replications in a completely randomized design. We monitored ammonium-N concentration ([NH4+-N]) in soil solution by repeatedly taking samples from a porous tubing (10-cm long) vertically inserted at the most distant point from surrounding rice hills. Samples were taken in triplicate (= triplicate tubes) and every three days from transplanting in each experimental unit. For above-ground attributes, leaf area index (LAI) was measured in 2012, whereas soil coverage ratio was estimated by image processing in 2016. Results showed that [NH4+-N] increased gradually after transplanting and then rapidly decreased from a certain day. This distinct drop in [NH4+-N] informed us the timing at which the rice root system reached the point of porous tubing and thus essentially covered the whole soil volume. The LAI at the dropping point was about 0.43 regardless of the cropping schedules in 2012 experiment. In 2016, the coverage ratio at the N dropping point was within the range of 0.12 to 0.19 for four genotypes having different growth durations. In addition, the coverage ratios at seven weeks after the transplanting showed a good correspondence to LAI across the four genotypes. We therefore conclude that both LAI and coverage ratio may serve as robust indicators for root development and might be useful to estimate the timing when the root system fully cover the soil volume. Results obtained here will also contribute to develop models that can predict not only above-ground canopy development but also associated below-ground processes.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.34 no.s02
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• pp.66-80
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• 1989

Salt injury in rice is caused mainly by the salinity in soil and in the irrigated water, and occasionaly by salinity delivered through typhoon from the sea. The salt concentration of rice plants increased with higher salinity in the soil of the rice growing. The climatic conditions, high temperature and solar radiation and dry conditions promote the salt absorption of rice plant in saline soil. The higher salt accumulation in the rice plant generally reduces the root activity and inhibits the absorption of minerals of rice plant, resulting the reduction of photosynthesis. The salt damages of rice plant, however, are different from different growth stage of rice plants as follows: 1. Germination of rice seed was slightly delayed up to 1.0％ of salt concentration and remarkably at 1. 5％, but none of rice seeds were germinated at 2.5％. This may be due to the delayed water uptake of rice seeds and the inhibition of enzyme activity, 2. It was enable to establish rice seedlings at seed bed by 0.2％ of salt concentration with some reduction of leaf elongation. The increasing of 0.3％ salt concentration caused to the seedling death with varietal differences, but most of seedlings were death at 0.4％ with no varietal differences. 3. Seedlings grown at the nursery over 0.1％ salt, gradually reduced in rooting activity after transplanting according to increasing the salt concentration from 0.1％ up to 0.3％ of paddy field. However, the seedlings grown in normal seed bed showed no difference in rooting between varieties up to 0.1％ but significantly different at 0.3％ between varieties, but greatly reduced at 0.5％ and died at last in paddy after transplanting. 4. At panicle initiation stage, rice plant delayed in heading by salt damage, at meiotic stage reduced in grains and its filling rate due to inhibition of glume and pollen developing, and salt damage at heading stage and till 3 weeks after heading caused to reduction of fertilization and ripening rate. In viewpoint of agricultural policy the overcoming strategy for salt injury is to secure sufficient water source. Irrigation and drainage systems as well as underground drainage is necessary to desalinize more effectively. This must be the most effective and positive way except cost. By cultural practice, growing the salt tolerant variety with high population could increase yield. The intermittent irrigation and fresh water flooding especially at transplanting and from panicle initiation to heading stage, the most sensitive to salt injury, is important to reduce the salt content in saline soil. During the off-cropping season, plough and rotavation with flooding followed by drainage, or submersion and drainage with groove could improve the desalinization. Increase of nitrogen fertilizer with more split application, and soil improvement by lime, organic matter and forign soil addition, could increase the rice yield. Shift of trans-planting is one of the way to escape from the salt injury.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.34 no.3
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• pp.310-323
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• 1989

This study was carried out to find out the difference of ripening and growth characteristics among the different florets in same panicle. There were 2 different transplanting date (May 25 and June 10) and 6 varieties were used. Physiological ripening period, ripening speed, 1000 grain weight, germination speed and grain quality were studied among the different florets (1, 5 and 8 days after heading) in same panicle. Physiological ripening period was long in late transplanting, late flowering floret, and late varieties by 3-9 days in Japonica. Ripening speed and 1000 grain weight were high in early transplanting and early flowering florets. There was positive correlation among the ripening speed, 1000 grain weight and a average temperature but negative correlation between the ripening and physiological ripening period. Germination speed was excellent in early flowering floret after heading. There was difference in amylose content within varieties and different flowering grains and there was significant correlation between grain quality and meteorological factors in some varieties.

• Korean Journal of Plant Resources
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• v.26 no.4
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• pp.503-510
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• 2013

This study was conducted to determine the optimum intensity of root pruning and the initial seedling size of 1-year-old Quercus serrata for producing 2-year-old healthy seedlings. Large( > 26 cm hight) and small size ( < 24 cm hight) seedlings were pruned their root by the length of 5, 10, and 15cm and then transplanted on nursery. Stem height, root-collar diameter(RCD), height to RCD ratio(H/D ratio), shoot dry weight(DW) and root development were measured during first growing season after transplanting. Seedling size and pruning intensity influenced on shoot growth such as height, RCD, H/D ratio and DW after transplanting. In addition, the development of lateral roots such as number, length, DW and diameter were affected by the seedling size. Taproot pruned by 15cm was shown excellent above-ground growth in large seedling group, but pruned by 10 and 15cm showed respectively better shoot growth in small seedling group. Large seedlings increased their above-ground growth, taproot regrowth, and number of lateral roots more than those of the small seedlings. But the length and DW of lateral roots were increased in the small seedlings. In conclusion, in order to produce high quality 2-year-old seedlings, it is important to produce large size of Q. serrata seedlings. Also root pruning length of 1-year-old Q. serrata was reasonable on 15 cm in taller than 26 cm or 10cm in less than the height.

• Journal of Bio-Environment Control
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• v.18 no.1
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• pp.51-59
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• 2009

Bulb onion cultivation area has been restricted in southern part of Korea to avoid blotting and bulb division. The traditional culture method is transplanting bare-rooted plantlet into the field at the end of summer and harvesting at the beginning of next summer. The hot weather and weak plantlets occasionally causes unstable supply of onions in autumn. In order to enlarge cultivation area and to reduce culture period, long nursery system using plug tray and spring transplanting was tried. Forty cultivars collected from Korea and Japan were nursed using 200-plug tray and transplanted to the field in spring. Marketable yield was not related to the seedling size but lodging time. Cultivar of 'Hamasodachi' was lodged early and resulted low marketable yield. Cultivar of 'Cheonjudaego' was not lodged and yielded high but not in accordance with storability. Generally early lodged cultivars showed low storability. In order to avoid rainy harvesting season, cultivars requires excessive long time for lodging is not recommended for spring culture. Using plug nursery and spring transplanting, we successfully produced marketable onions in 3 months. But immediate using of the harvested onion is recommended. The storability of produced onions showed different result among cultivars, storage of spring onion was not recommended.