• Weed & Turfgrass Science
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• v.3 no.2
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• pp.78-85
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• 2014

The survey of weed occurrence was conducted to identify dominant weed species in the paddy field. Total 346 sites of the 12 regions in Chungbuk Province in Korea were investigated in July, 2013. Weed flora was composed of 43 species belonged to 15 families. The compositions of major plant families, Cyperaces, Poaceae, Pontederiaceae and Asteraceae, were 21.5, 17.4, 15.5 and 12.7%, respectively. Based on life cycle, weed species was grouped into annuals of 71.3 and perennials of 28.1%. The most dominant weed species in paddy fields of Chungbuk Province were Monochoria vaginalis (14.5%), followed by Scirpus juncoides (10.5%), Echinochloa oryzoides (9.3%), Eleocharis kuroguwai (7.0%), Aeschynomene indica (6.2%) et al. The similarity of paddy weeds in 12 regions observed through TWINSPAN analysis was distinguished by Persicaria longiseta, Aneilema keisak, Persicaria thunbergii, Fimbristylis millacea, Blyxa japonica, Digitaria ciliaris, Potamogeton distinctus, Cyperus nipponicus. This information could be useful for estimation of future weed occurrence and establishment of weed control methods in chungbuk province in Korea.

• Weed & Turfgrass Science
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• v.2 no.4
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• pp.341-347
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• 2013

The survey of weed occurrence was conducted to identify problematic weed species on the paddy field. Total 524 sites of the 17 regions in Chungnam Province in Korea were investigated from June to August, 2013. In the whole region, 23 weed species were identified including 19 annuals and 4 perennials. The most dominant weed species in Chungnam paddy fields were Echinochloa crus-galli (25.3%), followed by Monochoria vaginalis (11.9%), Eleocharis kuroguwai (10.3%), Bidens tripartite (9.3%) and Aneilema japonicum (8.5%). The 95.2% of the investigation sites was determined under dominance value 1 (range of cover <10: numerous individuals) by Braun-Branquet indicating proper weed control in the paddy fields. This information could be useful for estimation of future weed occurrence, weed population dynamics and establishment of weed control methods in Chungnam Province in Korea.

• Weed & Turfgrass Science
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• v.2 no.4
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• pp.358-361
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• 2013

This study was conducted to determine the weed control effect of false seedbed in organic rice paddy field. False seedbed is one of the preventative weed control method, especially effective in upland vegetable field. False seedbed frequency and methods were examined by varying the processing time in greenhouse and field condition in 2012 and 2013. In greenhouse experiment, shallow recultivation and harrow surface soil was effective to control weed up to 70%. Optimal processing time of false seedbed was when the weed was two or three leaf stages. Under field condition, one-time treatment of false seedbed was 61% of weed suppression rate and two-times of false seedbed treatment was 79% of weed suppression rate. Monochoria vaginalis was still troublesome weed after false seedbed treatment, but the occurrence of Echinochloa oryzoides was decreased after false seedbed treament. Results indicated that false seedbed treatment was very effective to lower early weed occurrence in rice paddy field especially Echinochloa spp. Weed control efficiency of shallow recultivation by weeder hollow and rotary tillage by tractor were 68%, 13% respectively.

• The Korean Journal of Pesticide Science
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• v.3 no.1
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• pp.1-12
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• 1999

Herbicidal activities of newly synthesized experimental compound, KSC-13906 [Erythro N-{(4,6-dimethoxy pyrimidin-2-yl)aminocarbgnyl}-2-(2-fluoro-1- hydroxy-n-propyl)benzenesulfonamide, US Patent 5,461,025], were investigated in greenhouse and field for development as a paddy herbicide. KSC-13906 exihibited excellent weeding effects and selectivity to rice under submerged paddy condition in geenhouse. At the application rate of $2.5{\sim}5$ g ai/ha treated on surface of water, KSC-13906 effectively controlled three annual weeds such as Echinochloa crus-galli var. oryzicola. Scirpus juncoides, and Monochoria vaginalis as well as five perennial weeds such as Cyperus serotinus, Sagittaria pygmaea, Eleocharis kuroguwai, Potamogeton distinctus, and S. trifolia. However, there was no effect on Aneilema keisak and Lindernia procumbens. Especially, KSC-13906 effectively controlled Echinochloa crus-galli var. oryzicola at growth stages ranging from pre-emergence to 3-leaf stage. Antagonistic interaction was found between pyrazosulfuron-ethyl and mefenacet, but not between KSC-13906 ana mefenacet. KSC-13906 had high selectivity to transplanted rice, but caused phytotoxic effect on direct-seeded rice when treated before 3-leaf stage. Herbicidal activity of KSC-13906 on the Echinochloa crus-galli var. oryzicola was 7-folds greater than that of pyrazosulfuron-ethyl in terms of relative dose ratio of the herbicides. These results suggest that KSC-13906 possesses selective herbicidal potency in rice.

• Korean Journal of Weed Science
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• v.1 no.1
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• pp.21-29
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• 1981

Nationwide survey of weed population in paddy rice field was conducted from 1760 fields all around Republic of Korea in 1981. The weed species observed include 2 species of grasses, 7 species of sedges, and 18 species of broadleaf weeds, and the dominant weed species were Monochoria vaginalis, Sagitraria trifolia, Potamogeton distinstus, Sagittaria pygmea and Cyperus serotinus. More and many weeds were growing in single cropped field than double cropped field. In single cropped fields, weed population was reduced when autumn plowing was conducted. In double cropped fields, more weeds were growing in barley or wheat grown fields than vegetable gown fields. Among the five paddy soil types, more weeds were growing in saline soils and poorly drained soils than others. The proportion of annual and perennial weeds in national average was 44% and 56%, and perennials became more dominant in central part of the peninsula. Autumn plowing and double cropping appeared to reduce the perennial weed population, however, the increased perennial weed population, presumably due to continuous use of herbicides which controls mostly annuals, seemed to an urgent problem to be solved.

• Korean Journal of Weed Science
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• v.13 no.2
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• pp.159-163
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• 1993

This research was conducted at the Crop Experiment Station to determine the changes of weed flora under direct seeded rice cultivation in dry paddy field from 1989 to 1992 and to establish an effective weed control strategy in direct seeded rice cultivation. With the continuous rice growing under direct seeded rice cultivation in dry paddy field, there were more occurrence in grasses and annual weeds while broadleaf and perennial weeds were diminished. The predominant weeds were aquatic weeds such as Eleocharis kuroguwai, Echinochloa crusgalli, and Monochoria vaginalis in machine transplanted rice paddy field while there were predominant of semi aquatic weed species such as E. crusgalli, Digitaria sanguinalis, Bidens tripartita, Aeschynomene indica, and Arthraxon hispidus in continuous direct seeded rice cultivation in dry paddy condition. Based on the vegetative analysis of weeds in terms of simpson index and community dominance, there was more distribution of weed species in direct seeded rice cultivation on dry paddy condition while only distributed with 1-2 weed species in machine transplanted rice paddy field. In similarity coefficient, there was a gradual increase up to 67% of weeds with the continuous direct seeded rice cultivation in dry paddy condition for 4 years starting from 41% of similarity coefficient.

• Weed & Turfgrass Science
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• v.2 no.3
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• pp.318-321
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• 2013

National Academy of Agricultural Science and eight province Agricultural Research & Extension Services investigated the occurring area of herbicide resistant weeds in paddy field of Korea. In order to estimate the occurring areas of herbicide resistant weeds, we collected paddy soils randomly from 3,200 sites in 2011 and 2012, and treated 30 kg $ha^{-1}$ of pyrazosulfuron-ethyl+pyriminobac-methyl GR to the paddy soil. 176,870 ha, approximately 22.1% of cultivated area excluding organic and eco-friendly cultivated area, was estimated to be infested by SUherbicide resistant paddy field weeds. Several species of resistant weeds were occurred at Jeonranam-do with 44.3%, followed by 30.5% at Chungchungnam-do, 27.8% at Chungchungbuk-do, and 24.5% at Jeonrabuk-do, respectively. Monochoria vaginalis showed the highest distribution with 57,018 ha, 32.2% followed by Scirpus juncoides, and Lindernia procumbens, respectively.

• Korean Journal of Weed Science
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• v.16 no.1
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• pp.8-13
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• 1996

This study was conducted to know the effect of storage period, harvesting time and light condition on dormancy breaking of major weeds. Echinochloa crus-galli, Cyperus serotinus, Aeschynomene indica, Ludwigia prostrata and Bidens tripartita had the 10 or 30% germination ability within 30 days after harvest but scirpus juncoides, Potamogeton distinctus, Aneilema japonica and Monochoria vaginalis had not germination untill 120 days after harvest of seed. C. serotinus and P. hydropiper required strong light for germination but S. juncoides, L. prostrata and B. tripartita showed the less tham 5% germination in the dark condition gerntinator. S. juncoides germination showed negative response in chemical soaking but A. japonica, B. tripartita and L. prostrata showed high germination percentage in Acetone, Chloroform and distilled water soaking during the 10 days after treatment.

• Korean Journal of Weed Science
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• v.18 no.1
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• pp.12-19
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• 1998

The pattern of rice cultivation in Korea is changing from hand transplanting and machine transplanting into direct-seeding for low input and cost-down practices. However, there are still some obstacles to establish the direct-seeding cultural practices because of poor seedling stand, lodging, and weed infestation. In particular, there were much more and wide weed occurrence in direct-seeding rice as compared with the transplanted rice. Weed occurrence in terms of dry weight of weeds was highest in dry direct-seeded rice followed by sowing an puddled soil, sowing on submerged soil in order as compared with transplanting with infant rice seedling. Echinochloa crux-galli was a common dominant weed with 35~44% distribution in any direct-seeding methods. The dominant weed species were E. crux-galli, Cyperus difformis, C. serotinus, and Ludwigia prostrata in dry-seeded rice. The dominant weed species in water-seeded rice were E. crus-galli, Eleocharis kuroguwai, Scirpus juncoides, and Monochoria vaginalis. Yield loss of rice due to weeds at weedy condition was 96% in dry direct-seeded rice. In water-seeded rice, yield loss was 61%, whereas yield loss was 40% in machine transplanting with infant rice seedling.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.26 no.4
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• pp.287-292
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• 1981

The field studies were carried out in paddy field over a four year period in order to find out the effects of butachlor, nitrofen, oxadiazon or CG 102, benthiocarb-S, and bentazon applied successively to the same paddy field for four years on weed succession and rice yields under different fertilized conditions including compost, chemical fertilizer and straw application. Total dry weight of weeds was steadily increased yearly over 4 year period regardless of fertilized conditions, and significantly higher increase of weed dry weight was observed on non-fertilized and compost plots. The most dominant weed species was Scirpus hotarui, and Potamogeton distinctus, Eleocharis kuroguwai and Cyperus serotinus were predominated on compost plot, E. kuroguwai and E. aclularis on non-fertilized plot, E. kuroguwai, C. serotinus, and Monochoria vaginalis on chemical fertifizer plot, and C. serotinus on straw plot. When the same herbicides were used continuously on the same plots, weed control effect was decreased and thus weed population was greatly increased particularly on butachlor and nitrofen treated plots. P. distinctus, E. kuroguwai, and C. serotinus were predominated on butachlor treated plot, P. distinctus and C. serotinus on nitrofen treated plot, C. serotinus on benthiocarb-S treated plot, C. serotinus and P. distinctus on oxadiazon or CG 102 treated plot and P. distinctus on bentazon treated plot. Annual weeds were slightly increased by repeated annual application of oxadiazon or CG 102 and benthiocarb-S, whereas perennial weeds were predominated by successive application of butachlor, nitrofen. and bentazon for 4 years. Yield reduction of rice became prominent by successive application of same herbicides. particularly butachlor and nitrafen. This results suggested that successive annual application of same herbicides should be limited and herbicide combination or herbicide rotation should be applied to control the remaining weed species.