• Korean Journal of Weed Science
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• v.6 no.1
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• pp.48-58
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• 1986

In order to eluciate the factors affecting the injury caused by simetryne(2-methyl thio-4,6-bis(ethylamino)-S-triazine) to rice plants of Tongil variety(Indica ${\times}$ Japonica), the leaching properties of simetrynes, compared with Japonica varieties, Mangyeung and Sadominori were investigated. Bioassay technique and $^{14}C$-simetryne for leaching study and bioassay for the characteristics of the rice plants were employed. The leaching range of simetryne was very narrow regardless of soil types under upland soil conditions but it increased little in Silt clay soil and greatly in Sandy loam soil under flooded soil conditions. The amount of the roots of Tongil Jas a little more than that of Mangyeung and the roots of the Tongil mostly distributed near the surface soil while those of Mangyeung rooted deep into the soil. The foliage area and the rate of transpiration of Tongil were larger and greater than those of Mangyeung by 1.3 times and 1.65 times, respectively. The sensitivity of Tongil to simetryne was about 3 times larger than that of Sadominori in water culture.

• Korean Journal of Soil Science and Fertilizer
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• v.13 no.3
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• pp.85-91
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• 1981

In order to evaluate effectiveness of zinc source on uptake of zinc by rice plant, a pot experiment carried out using ZnEDTA and $ZnSO_4$ in a glasshouse. The results obtained were summarized as follows: The effectiveness of zinc source on uptake of zinc by rice plants was different with different soil. Namely ZnEDTA was more efficient than $ZnSO_4$ in increasing yield of zinc and concentration of zinc in the plant grown on Jecheon calcareous soil. In case of Keumgok acid soil, however, no superiority of ZnEDTA treatment was found. The plant growing status of ZnEDTA treated calcareous soil was also shown that larger number of tillers per hill, bigger height of the plant and good yield of dry matter production than those of the plant grown on $ZnSO_4$ treatment. Regardless of the zinc source, smaller number of tillers per hill, shorter height of the plant, and the lowest yield of dry matter were shown in the treatment of zinc and straw mixed with both soils. It seemed that more applied zinc was to be fixed by the straw application resulting in poor zinc yield. The extent of the zinc fixation showed markedly in Jecheon calcareous soil.

• The Korean Journal of Pesticide Science
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• v.7 no.3
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• pp.182-187
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• 2003

In order to elucidate a degradation characteristics of herbicide mefenacet in soil, the persistence in soils was studied under laboratory conditions for $90\sim120$ days at $28^{\circ}C$. Mefenacet residues were determined from the two soils which pre-treated by sterilization and flooding, respectively. Non-sterilized upland soil was used as a control. When 70 days elapsed from application time, $55\sim63%$ of mefenacet applied were dissipated in control soils. However, $32\sim33%$ of mefenacet applied were dissipated in the sterilized soils and $33\sim35%$ was dissipated in the flooded soils. 까 lese results indicated that the degradation of mefenacet was assumed to be due to microorganism, especially aerobic microbes. In order to elucidate the influence of water content on the persistence of mefenacet in soil, water content in soils was adjusted to 20, 50, and 80% of the water-holding capacity(Field capacity, WHC). The half-life of mefenacet in soil containing 20% and 50% of WHC were 82 and 73 days, respectively, after incubation for 90 days. However, the half-life in soil containing 80% of WHC was shortened to 61 days. These results indicated that degradation of mefenacet in soil was influenced by the activity of soil microorganism, organic matter content and water content.

• Korean Journal Plant Pathology
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• v.11 no.1
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• pp.94-97
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• 1995

In 1994, an abnormal rice growth was observed in a 0.5-ha scale farmer's field located at Chogye-Myeon, Hapcheon-Gun, Gyeongnam Province where rice cv. Hwayeongbyeo was seeded directly in dry paddy field conditions. The major symptoms were less stands per acreage, short leaf length, and hypertrophy of root tip portion. The disorder was identified as rice seeding bight caused by Rhizopus sp. The average plant stand per m2 in the infested field was 108, while it was 375 in the normal field, and leaf growth was retarded to less than one-third of healthy plant. The average leaf lengths of infected and healthy seedlings were 12.8cm and 38.9cm, respectively. When the infected seedlings were transplanted to pots, flooded-soil conditions developed no new root growth but upland conditions allowed 11.2 new roots emerging. The length of newly emerged root in infested soil was 5.3cm in upland and 7.1cm in intermediate flooding conditions. However, it was 10.9cm in non-infested soil with intermediate flooding conditions. When the plants were matured, the stem length of infected plants was reduced slightly as compared to normal plants, whereas the length of panicle was not significantly different between infected and healthy plants. The number of panicle per plant, however, greatly different with variation of infection degree. Grain quality such as the number of complete and incomplete grains per panicle, the complete grain weight per panicle, and the weight of 1000 grains was not significantly different.

• Asian Journal of Turfgrass Science
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• v.9 no.1
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• pp.11-42
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• 1995

The investigation was made on the relationship among vegetation, net productivity, regrowth and soils of Moonheri-Wasoori, Soodowon-Sungilkyo and Mt. Kumhak grasslands in Chulwon area. The following conclusions have been made as the results of this study. The vascular flora of the grassland in Moonheri-Wasoori was composed of 102 species, the most of which were Medicago denticulata, Miscanthus sinensis, Arundinella hirta, Festuca ovina and Cassia nomame. The flora of Soodowon-Sungilkyn grassland was composed of 74 species, the most of which were Arundinella hirta, Miscanthus sinensis, Carex nanella, Festuca ovina and Cassia nomame. It of Mt. Kumfiak grassland was composed of 78 species, the most of which were Arundinella hirta, Carex nanella, Festuca ovina, Miscanthus sinensis and Aster scaber. These five species contributed greatly to the standing crop of live material which was in excess of 60% of it. The peak standing crop of each 413.7, 307.6 and $348.7g /m^2$ in Moonheri-Wasoori, Soo- dowon-Sungilkyn and Mt. Kuruhak grasslands wars reached in August under flooded conditions as a result of the growth of dominant species, Medicago denticulata and Arundinella hirta. The net prodution of organic matter was slight in some intervals but occurred throughout the growing season After cutting of grasses, the regrowth of new leaves mainly depended on growing stage and edaphic factors. Characteristics of the natural grassland soils, especially, concerning water, total nitrogen, avail-able phosphorus and exchangeable calcium were clarified and might be depend upon the quantity of plant production. Nitrogen, phosphorus and calcium concentration of leaves of Medicago denticulata, Arundinella hirta and Miscanthus sinensis were higher than of stems. Even if diem we diffurmem in the a-mb of nutrients among Medicago denticulata hirta and Miacanthus sinensis for single species and stands. they were covered by variations within species in the present survey. Key words: Competition, Production, Productivity, Regrowth, Soil Properties, Vascular Flora.

• Korean Journal Plant Pathology
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• v.3 no.4
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• pp.252-260
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• 1987

Incidence of lettuce drop was observed throughout the growing season in the vinylhouse at the southern part of Korea, Kimhai. Occurrence of this disease was especially severe at the seedling stage. Number of sclerotia in surface soil $(30\times30\times5cm)$ was 22.0 at the seedling stage, and 5.3 at harvest in the infected area. Temperature for mycelial growth ranged from 5 to $30^{\circ}C$ with optimum temperature at $25^{\circ}C$. Sclerotia were formed fewer at low temperature, but their size was larger resulting in heavier dry weight than that at high temperature. The apothecia were formed from the sclerotia that were buried in March, April and September upto 3cm soil depth, but formed from those buried only 1 em soil depth in October. Sclerotia buried in June and December did not form apothecia regardless of soil depth by 90 days. The sclerotia buried in the 5cm of soil depth did not form apothecia. Sclerotia that were embedded in wet or flooded soil at $25^{\circ}C$ and $30^{\circ}C$ for 5 weeks lost their viability. Infection of lettuce was possible with mycelia originated from sclerotia on autoclaved lettuce plant fragments. The fungus was pathogenic on 25 plant species in 8 families in artificial inoculation tests. Lettuce seedlings appeared to be infected by airborne ascospore originated from sclerotia on crops and weeds around paddy fields, because sclerotia existing in soil might perish under long flood conditions during rice cultivation.

• Korean Journal of Soil Science and Fertilizer
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• v.30 no.4
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• pp.309-313
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• 1997

Field experiments were conducted on Jeonbug series (Fine silty, mesic family of Aeric Fluventic Haplaquepts), to study the effect of split application of N fertilizer in combination with rice straw on N use efficiency of dry-soil-direct seeded paddy rice. Treatments involved conventional application of N (in three splits; 40% at planting, 30% at five leaf stage and at heading stage) without rice straw, all basal application of N with straw application (5000 kg/ha), N application in two splits (70% at planting and 30% at heading stage) with rice straw application and N application in three splits (40% at planting, 30% at five leaf stage, 30% at heading stage) with application of rice straw. There was Zero N plot too for the estimation of N use efficiency. Seeding was done on dry soil and the filed was flooded 32 days after seeding. The fertilizer application rates were 160, 70, and 80 kg/ha of N, $P_2O_5$ and $K_2O$, respectively. The experiment was conducted for two years, in the same filed. The apparent use efficiency of fertilizer N by rice tended to be higher under the application of rice straw when N was applied in three splits. This, however, did not increase the yield of rice significantly. Even under the application of rice straw, the apparent N use efficiency was lower when N fertilizer was applied in one dose at the planting and in two splits. The lower N use efficiency in these cases, did not yield of rice significantly. The periodical analysis of mineral N in the soil suggested that higher mineral N in the soil at the early stages was responsible for the lower apparent N use efficiency.

• Korean Journal of Soil Science and Fertilizer
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• v.16 no.3
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• pp.210-222
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• 1983

The chemical factors of topsoil, which are associated with the prediction models of urea nitrogen (N kg/ha) need under the concept of multinutrient factor balance in soil to maintain optimum nutrient balance in rice plant grown in flooded condition, were the x/z and the Kas/Kai values. In the prediction model or equation $NRe=(58.5+0.647x/z){\cdot}F$, the F was difined as the productivity factor, which was considered to be dependent on the variety, climate and soil, and found to be better estimated as the function of Kas/Kai rather than x/z from the equation Fb=0.65+1.086kas/kai, where the x, z, Kas and Kai, respectively, were available $SiO_2$ ppm, % organic matter, K activity ratio or exchangeable $K^+/(\sqrt{Ca+Mg}+Na^+)$ in topsoil and the ideal K activity ratio determined by the equation Kai=0.03+0.00083x/z for standard variety Jinheung. The relative K activity ratio or Kas/kai in topsoil, which have to be equal to 1.0 in the prediction of K fertilizer need for standard Japonica Variety Jinheung, found to be 1.63 for the varieties of Indica ${\times}$ Japonica or Milyang No. 23 grown in Korean condition and 0.322 for the Indica varieties of IR 8, 20, 36 and 42 gown in the Philippines condition. The ideal K activity rations for different Varieties such as Indies ${\times}$ Japonica grown in Korea or $Kai_1$ and Indica grown in the Philippines or $Kai_2$ were computed to be estimated from the following equations respectively ; $\\Kai_1=0.0489+0.001353X/Z\\Kai_2=0.01+0.000267X/Z$.

• Korean Journal of Environmental Agriculture
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• v.9 no.2
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• pp.83-95
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• 1990

This study was conducted to estimate influences of pesticides such as carbofuran[2,3-dihydro-2,2-dimethylbenzofuran-7-yl methyl carbamate] as an insecticide, and pyrazolate [4-(2,4-dichlorobenzolyl)-1,3-dimethyl-5-pyrazolyl-1,3-dimethyl-5-pyrazolyl-p-toluensulfonate], pyrazolate+pretilachlor [2-chlor-2,6-diethyl-N-(n-propoxyethyl) acetanilied] as herbicides on change in numbers of soil microorganisms and pH in planted and unplanted flooded rice paddy soils. The results of weekly investigated change of pH and populations of total bacteria, gram negative bacteria, anaerobic bacteria and fungi after treatments of pesticides were as follows : The change of pH in rice-planted soil gradually decreased in a matter of weeks after treatment with pesticide and the pH increased again from the sixth week, but no change of pH could be observed in nonplanted soil. The total numer of bacteria in the treated plots were slightly less than in the control plot, and the numbers decreased with increasing application rates of pesticides. But the microbial population increased in a matter of days after treatment with pesticide. Number of the gram negative bacteria until the sixth week after treatment of pesticide were fewer than control. The number in the carbofuran-treated plot decreased after a weeks after treatment, but numbers in plots treated with pyrazolate and pyrazolate+pretilachlor increased. The number of anaerobic bacteria in the treated plots were few by comparison with the untreated control, but the number increased after a weeks after treatment with pesticides. The populations of fungi in the carbofuran-treated plot were similar by comparison with the untreated control. The populations in the plots treated with pyrazolate and pyrazolate+pretilachlor decreased in 4 to 5 weeks with increase of application rate, but afterwards increased.

• The Journal of Natural Sciences
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• v.5 no.2
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• pp.49-62
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• 1992

This study was carried out to investigate the emergence, growth and yield components in rice inassoccation with Several cultivation methods direct sowing flooded paddy field(DSF), direct sowing by airplane(DSA), direct sowing in dry paddy field(DSD), 8days seedling planting(8DS), and 35days seedlingplanting(35DS). Also this study was attempeted to know the effects of calcium peroxide on germinationand early growth of rice under different soil conditions, seeding depth, application of organic matter,indirect sowing flooded paddy field.1. Rate of emergence was 73% in DSF, 70% in DSA, 62% in DSD, respectively, under the different cultivation method of rice in reclaimed paddy field.2. Degree of lodging in relation to cultivation was 5 at both DSF and DSA, 3 at DSD, 2 at both 8DS and 35DS respectively.3. Maximum tiller number was 568 per m2 at DSF and 527 at DSA. Heating was delayed for 4 days at DSF, 8 days at DSD and 2 days at 8DS as comparison with that at 35DS.4. Yield was higher 1% to 3% at DSF than that at DSA and DSD while decreased by 12% as compared with that of seedling planting.5. Total dry weight of seedling was decreased by 57% at 8DS, 60% at DSF 63% at DSD, respectively, under 0.3% of salinity. Ratio of decreasing in dry weight was higher with high salinity.6. The amount of O2 released was recorded highest to 2 to 3days after irrigatition, thereafter remaining constant to 10 days after irrigatition.7. The optimum coating amount of calcium peroxide for germination was a half of rice seed weight with 1 cm sowing depth and one-fold with 2-cm sowing depth when rice straw was not applied. With rice straw applied, on the other hand, the amount of peroxide was one-fold with 1-cm sowing depth. It was found that, under the condition of applied 600kg/10a, of 2-cm soil depth with rice straw calcium peroxide coating had no effect on emergence of rice seedling.8. In reclaimed paddy field, lodging degree was 7 with direct sowing by machine and 9 with direct sowing by hand.9. Yield was increased by 5% by applying rice straw with direct sowing by machine.