• KOREAN JOURNAL OF CROP SCIENCE
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• v.58 no.4
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• pp.393-398
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• 2013

Lodging in the direct seeded rice cultivation on flooded paddy is being severe problem due to the lower production and grain quality at ripening stage. This study was conducted to examine the effect of Iprobenfos-metconazole (IPM) treated 50, 40 and 30 days before heading respectively as a plant regulator to reduce the lodging at ripening stage of direct seeding rice cultivation. The culm length treated with IPM, especially the 4th culm internode, was shortened more than with untreated plot, and the most effective time was at 30 days before heading. At 20 days after heading the flag leaves colour showed more greening than in the untreated leaves and the plot with IPM treatment was to be maintained longer compared to the control plot. The Nitrogen concentration of leaves with IPM was lower than in the control plot, and $SiO_2$ contents were higher than in the untreated plot and $SiO_2/N$ ratio was increased more in the IPM plot than in the control plot. The breaking strength of 3rd and 4th culm internode with IPM treatment was higher than in the untreated plot, and the lodging index was reduced in the IPM plot significantly and the field lodging also was reduced. As the results the rice production in the IPM plot was increased more due to be higher ripening ratio and seed grain weight compared to the untreated plot to be occurred the field lodging.

• Journal of Environmental Impact Assessment
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• v.31 no.5
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• pp.296-309
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• 2022

This study investigated the mobility of inorganic elements (As, Cd, Pb, and Zn) that existed as acid extractable and reducible forms in flooded soils with a pot experiment involving rice cultivation. In general, it is known that soil inorganic elements that existed as an acid extractable form which includes exchangeable, carbonates, non-specifically sorbed, and specifically sorbed have mobility. However, the result of the experiment revealed that each inorganic elements of rice roots grown from flooded soils had different characteristics. The concentrations of Arsenic existed as both forms and the concentrations of cadmium and lead existed as a reducible form in the soils showed a high causal relationship with the concentrations of those elements in the roots of rice plants. The concentrations of zinc, an essential plant element, didn't show a causal relationship. Therefore it is necessary to consider the soil's environmental characteristics such as drained/flooded condition, oxidation/reduction condition, etc. for the mobility assessment of inorganic elements. The concentrations of the reducible form of arsenic, cadmium, and lead in flooded environment such as a paddy field should be also considered because the mobility of these elements combined with Fe/Mn increases in the reduction condition.

• The Korean Journal of Pesticide Science
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• v.3 no.2
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• pp.90-93
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• 1999

Several vinylsulfonylphenyl triketones and 2-alkoxy- and 2-(N,N-diethylamino) ethanesulfonylphenyl triketones have been synthesized, and their herbicidal activities in flooded paddy field were studied. Herbicidal effects of vinylsulfonyl triketones 6a-c were not satisfactory, whereas 2-alkoxyethanesulfonylphenyl triketones 7a and 7b showed good herbicidal activities without meaningful selectivity to rice.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.31 no.2
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• pp.204-213
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• 1986

The objective of this paper was to examine the response of rice seedling emergence and early growth under the different temperature (day/night, 29/21$^{\circ}C$, 17/17$^{\circ}C$, 12/12$^{\circ}C$) and the different seeding depth (1 cm, 2 cm, 3 cm). The trial was carried out in the phytotron and field in the Crop Experiment Station, Suwon, Korea in 1985. Calcium peroxide-coated seeds were very effctive in promoting seedling emergence, seedling establishment and eary growth of rice. Coated seeds were more effective in low temperature condition (17/17$^{\circ}C$, 12/12$^{\circ}C$) than in high temperature (29/21$^{\circ}C$) at the phytotron trial. The deeper the seeding depth, the less the emergence and seedling establishment, and the available seeding depth was I cm in the direct seeding under the flooded soil. In the field trial (seeding date, May 1) the results for the emergence and seedling establishment were similar to those in the phytotron trial. Available cultivars for the direct seeding cultivation under the flooded soil were Cheonmabyeo, Namyangbyeo, Kihobyeo, Akibare, Nakdongbyeo and Dongjinbyeo in Japonica type, and Taebaegbyeo, Samgangbyeo and Gayabyeo in Indica x Jponica type. Coefficients of variation to the emergence and seedling establishment between rice cultivars were very high. Therefore, in the direct seeding cultivation under the submerged paddy, choice of rice cultivars and improved technique for direct seeding will be more necessary.

• Korean Journal of Agricultural Science
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• v.46 no.4
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• pp.857-868
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• 2019

A flooded rice field is one of the significant sources of anthropogenic methane (CH₄) with the intensity of the emissions dependent on management practices. Incorporation of rice straw, which is one of the organic amendments, induces the increase of methane emissions during the flooding season. In this study, we measured of methane emission according to applications of rice straw in different soil textures during a cultivation period in 2017 and 2018. The fallow treatments were non application of rice straw (NA), spring plowing after spring spreading of rice straw (SPSA), spring plowing after previous autumn spreading of rice straw (SPAA), and autumn plowing after previous autumn spreading of rice straw (APAA). The SPSA treatment emitted the highest total methane from loam soil in both 2017 (596.7 CH₄ kg ha^-1) and 2018 (795.4 CH₄ kg ha^-1). The same trend was observed in silt clay loam soil; the SPSA treatment still emitted the highest amount of methane in both 2017 (845.9 CH₄ kg ha^-1) and 2018 (1,071.7 CH₄ kg ha^-1). The lowest emission among the rice straw incorporated plots came from the APAA treatment for both soil texture types in all the seasons. The conversion factors of the SPAA were 0.79 and 0.65 from the loam and silt clay loam soils, respectively. Relatedly, the conversion factors of the APAA were 0.71 and 0.43 from the loam and silt clay loam soils, respectively. The above observations mean therefore that incorporation of rice straw early in the fallow reduces methane emissions in the main rice growing season.

• Korean Journal of Environmental Agriculture
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• v.31 no.4
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• pp.359-367
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• 2012

BACKGROUND: As natural wetlands are decreased by increment of human demand, the importance of rice fields as an alternative habitat for waterbirds is well documented. However, the relationship between waterbirds use and management practice of rice fields has not been fully understood. The present study attempted to understand the changes in temporal abundance of waterbirds and their preference for habitat types in rice fields all year round. METHODS AND RESULTS: Waterbirds census were conducted in rice fields around Asan bay in Korea during April 2009-March 2010 and April 2011-March 2012. In the bird counts, the locations of the observed birds on a 1/2,500 map were recorded along with the local habitat type (paddy, ditch, levee, road). Thirty five species of waterbirds recorded in the rice fields during the survey period and three major groups (shorebirds, herons, and waterfowls) were characterized according to season and micro-habitat use. Shorebirds visited a flooded paddy for feeding during their spring migration season (April-May), and herons used the rice field as feeding sites during their breeding periods (April-October). Most waterfowls were observed in a dry paddy to feed a fallen rice seed and stubs during the winter season (September-March). Waterbird groups selectively used micro-habitats in rice field. Shorebirds and waterfowls mainly preferred at rice paddies, while herons were attracted to most habitat types. CONCLUSION(S): Rice fields supported various waterbirds all year round and waterbird communities using the rice fields were dramatically changed according to seasonal change of rice field condition.

• Magazine of the Korean Society of Agricultural Engineers
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• v.21 no.3
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• pp.83-91
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• 1979

This study was conducted in order to find out the performance of rice transplanters in accordance with the change of the trans-planting days after pudding and the water depth flooding the paddy field at the time of transplanting : and thus to select the optimum paddy field preparation procedures for an efficient utilization of rice transplanters. The performance factors of the two different types of rice transplanters were measured during the first 6 consecutive days after puddling and with 3 different levels of water depth flooding the paddy fields. The results of this study were analysed and summarized as follows : 1. Wheel sinkage decreased very rapidly from 0 to 2 days after puddling and slowly from 3 to 5 days after puddling. 2. The depth of the test cone penetration decreased rapidly during the first few days after puddling. It was 17.8cm just after puddling, and decreased to 13.4cm one day after puddling. After 2 days, the rate of decrease was dampened, and after 5 days it kept constant value of 9.2cm. 3. Two days after puddling, the hill interval was 15.8cm (98.75% of the preset value) for broadcasted seedling rice transplanter with 3cm flooding depth : This value was the closest to the pre-adjusted value of 16cm. The general performance of broadcasted-seedling type rice transplanter was better than that of strip-seedling type rice transplanter. 4. Usually the working performance of a rice transplanter is evaluated with uniformity and adjustability of the hill intervals. The hill interval was the most uniform and closest to the pre-set value of 16cm when planted two days after puddling with 3cm of water depth. When it was inavoidable to plant 4 days after puddling with stripseedling type rice transplanter, it is advisable to let the water flooded somewhat deeper. 5. The percentage of missing hills including floating and burried seedlings was the highest just after puddling and ie decreased substancially until 3 days after puddling and then it increased again. Hence, the optimal time transplanting is to be between 2 and 3 days after puddling. 6. Better postures of planted seedlings were found when planter 2 days after puddling than 3 days after puddling. Six cm of flooding water depth always gave the best results with respect to the postures of planted seedlings. Broadcasted-seedling rice transplanter, in general, showed better posture of planted seedlings than did strip-seedling type rice transplanter. 7. Judging from the above results, the optimal conditions will be 3cm of flooding depth and transplanting between 2 and 3 days after puddling.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.39 no.3
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• pp.205-210
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• 1994

This experiment was conducted to investigate of soil hardening degree before sowing, furrow depth at sowing and flooding time after sowing at furrowing in flooded rice paddy field that many people have an interest in as direct sowing method most recently. As hardening period was increased, the percentage of seedling stand and seed floating at flooding were increased slightly, while buried depth of stem at maximum tillering stage and cone penetration depth were decreased, respectively. Therefore, optimum degree of soil hardening was about 3 days after draining, at this time, cone penetration degree was about 6~7cm. According to furrow depth was more and more deep, buried depth of stem was increased gradually, but percentage of seedling stand was decreased considerbly. Also, root distribution ratio on surpace horizon and lodging degree were increased gradually according to furrow depth become more and more shallow. As flooding time after sowing was late, percentage of seedling stand and panicle number per $m^2$ were decreased slightly. These results apparently indicated that sowing after 3 days hardening when cone penetration degree was 6~7cm, furrow depth 3~4cm degree and flooding time just after sowing the best method to good establish of seedling stand.

• Korean Journal of Soil Science and Fertilizer
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• v.28 no.4
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• pp.312-318
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• 1995

To investigate the effect of N split application on the increasing ratio of yield and the yield of rice, urea and slow-releasing complex for sideband placement of fertilizer were applied in Jeonbuk series of Honam plain area. Increasing ratio of yield by N split application was higher in puddled drill seeding (PDS) than flooded direct seeding surface (FDSS) under split application of 40-0-30-30% and 70-0-0-30% at basal, 3 leaf, 5 leaf and panicle initiation stage, respectively. It was also higher in LCU application of 70 % of total urea amount than urea application but was not different between two methods of seeding in urea application. Nitrogen ratio transfered to rough grain of rice was higher in FDSS than PDS, errespective of methed of split application, except for the split application of 0, 40, 30 and 30% N fertilizer at basal, 3 leaf, 5 leaf and panicle initiation stage, respectively. Nitrogen amount outflowed by artificial drainage for paddy field drying in a day after application of fertilizer was 1,134g/10a in PDS. $NH_4-N$ incerased higher in PDS than FDSS under split application of urea, while was versa under LCU application.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.41 no.3
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• pp.308-317
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• 1996

These experiments were conducted to investigate variation of physical characteristics of the culm related to lodging resistance by nitrogen levels under direct seeding on flooded paddy surface. The number of seedling per m$^2$ were from 103 to 110 plants, and seedling ratios were ranged from 66.7% to 71.2%. The lodging occurrence were increased in order to the nitrogen levels 15 kg, 10 kg, 5 kg /10a, and the lodging resistant varieties ; Dongjinbyeo and Cheongmyungbyeo showed less values of field lodging than those of lodging susceptible varieties ; Daecheongbyeo, Palgongbyeo and H waseongbyeo. The lodging resistance was decreased in semidwarf varieties compare with long culm varieties, but Dongjinbyeo, long culm variety has lodging resistance. The occurrence of lodging decreased with lower values in top moment, but with higher values in the breaking moment with leaf sheath. The root dry weight positively correlated with weight of culm base, but modulus of section was negatively correlated with bending curvature, respectively.