• Weed & Turfgrass Science
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• v.2 no.3
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• pp.254-259
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• 2013

The mechanisms of resistance to oxyfluorfen (OF) and paraquat (PQ) were investigated in rice plants. Examination of the concentration dependence of oxyfluorfen- or paraquat-induced increase in conductivity showed that conductivities in the OF- and PQ-treated leaf squares were increased with 0.1 ${\mu}M$ oxyfluorfen and 0.01 ${\mu}M$ paraquat and further increased with higher concentrations. The levels of conductivity were approximately 10-times higher in the PQ-treated plants than in the OF-treated plants, indicating that the PQ-treated plants suffered more severe photodynamic damage than the OF-treated plants. The photooxidative stress caused by foliar application of either 50 ${\mu}M$ oxyfluorfen or 100 ${\mu}M$ paraquat increased the enzyme activities of ascorbate peroxidase and peroxidase 1 day after the herbicide treatments and then further increased their enzyme activities 2 days after the treatments. The activities of catalase began to increase 2 days after the oxyfluorfen and paraquat treatments. These antioxidant enzymes appear to play an essential part of defense mechanisms against oxyfluorfen and paraquat. Our results demonstrate that paraquat caused more severe oxidative stress, as indicated by a greater change in conductivity, thereby resulting in greater increases in antioxidant responses in plants, compared with those of oxyfluorfen.

• Korean Journal of Weed Science
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• v.31 no.3
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• pp.260-270
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• 2011

This study was carried out to examine the effect of rice bran, barley bran, burned rice bran, and burned barley bran on the growth and yield of Chinese chive (Allium tuberosum Rottler), taro (Colocasia esculenta), and weed control. When the above 4 brans were examined 13, 27, 41 and 57 days respectively after application, the plant height of Chinese chive applied with burned barley bran was significantly higher than non-treated control, whereas the other brans did not have any distinct effect on the plant height or population number of Chinese chive. However, when examined 57 days after the application of the above 4 brans, all the plants applied with brans showed more than twice the improvement in shoot fresh weight compared with non-treated control. A chemical analysis of soil 57 days after the application of the above 4 brans showed that the soils were richer in available phosphate and organic matter. Shoot fresh weight of Chinese chive at 2 weeks after cutting was significantly higher in barely bran treated plot than in non-treated plot. In the case of taro, only taro plots transplanted when 10 cm tall and applied with barley bran showed an improvement in growth increment of both the underground and above parts. However, when sowed seeds after the application of the 4 brans, the yield of taro was reduced by the brans. Thus this research indicates that the effect of brans is differ based on the amount of bran application as well as crops. The effect of weed control on Echinochloa crus-galli, Digitaria clliaris, Chenopodium album, and Solanum nigrum as affected by brans was very low in pot conditions. Weed efficacy of the brans was also very low in field conditions. Growth of Chinese cabbage and garland chrysanthemum was inhibited 63% and 37% by rice bran at $4,000kg\;ha^{-1}$, respectively, but other crops such as maize, squash, cucumber, and Chinese chive were inhibited by 0-20%. These results were similar to that of barley bran except for Chinese cabbage.

• Korean Journal of Weed Science
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• v.10 no.2
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• pp.103-108
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• 1990

Germination test, nutrient culture test and pot experiment were conducted to determine selectivity of naproanilide between rice plants and paddy weeds. Naproanilide more severely inhibited growth of Scirpus juncoides, Sagittaria pygmaea and Cyerus serotinus than that of rice plant and Echinochloa crus-galli at germination stage. Root growth was severely inhibited than that of shoot growth by naproanilide treatment. Naproanilide severely inhibited rice plant and Echinochloa crus-galli at 30 uM, Sagittaria pygmaea at 1 uM and Cyperus serotinus at 10 uM in nutrient culture test, Rice plant and Echinochloa crus-galli did not show the difference of tillers and dry weight, but Scirpus juncoides, Morzochoria vaginalis and Aneilema keisak were severely inhibited at 15g/a and Sagittaria pygmaea and Cyperus serotinus at 30g/a in pot trial.

• Korean Journal of Weed Science
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• v.16 no.3
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• pp.171-175
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• 1996

Seed occurrence patterns of Echinochloa crus-galli (L) P. Beauv. and Monochoria vaginalis (Burm. f.) Presl. were investigated in irrigated and rainfed rice cultures. There was not much difference in seed population of E. crus-galli between irrigated and rainfed fields, but M. vaginalis occurred in about 1.6-fold greater number in rainfed fields. In seed distribution patterns under the two conditions, about 50% and 30% of E. crus-galli and M. vaginalis, respectively, were found in the uppermost 5cm layer. Under both conditions M. vaginalis was distributed to a depth of 25cm, but distribution of E. crus-galli was only 15cm deep. Early rice transplanting brought about greater emergence of the two weeds than optimal or late transplanting. Emergence of the weeds was significantly greater in single cropping system of rice than in double cropping systems of rice followed by barley and/or strawberry.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.1009-1020
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• 1996

Direct-seeded rice can have comparable yield with transplanted rice if its inherent problems can be solved. It is a labor-saving technology and can significantly reduce production cost because seedling nursery , pulling , and transplanting are omitted. Turnaround time between cropping is reduced hence the possibility of a third annual crop. But direct-seeded rice is very vulnerable to pest attack (by birds, rats, and golden snails), desiccation, weed infestation, and prone to lodging resulting to unstable crop establishment and inconsistent yield. These problems can be solved by anaerobic seeding (sowing pre-germinated seeds under the soil). It requires precise seed placement into the soil to optimize its benefits. We developed a four-row anaerobic direct seeder (US $ 200 commercial price) for this purpose . It consist of a structural framework mounted with a drum -hopper metering device, flotation type drivewheels, spring-loaded and adjustable furrow closers, and furrow open rs, and a plastic rainguard. It can sow in line pre-germinated seeds into the soil thus permitting the use of mechanical weeders for a chemical-free weed control. Its performance was comparable with the Japanese two-row anaerobic seeder (costing US$400) in terms of seed placement and crop establishment. It was tested with five cultivars. Seeding rate varied from 38 kg/ha to 80kg/ha. Crop establishment ranged from 64 to 99 percent while grain yield varied from 3.0 t/ha to 5.4t/ha. A six-row anaerobic seeder was also developed and adapted to a powertiller for increased capacity , field efficiency , and easier operation. The anaerobic seeder is useful to farmers shifting to direct seeding to reduce rice production cost and to researchers conducting agronomic studies in direct-seeded rice. Blueprint of the machine is available free of charge from IRRI.

• Weed & Turfgrass Science
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• v.2 no.1
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• pp.15-22
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• 2013

The phenotypic traits of herbicide-tolerant transgenic rice were compared with those of wild type (Dongjin) as well as two accessions (Hwaseong-aengmi 1 and Gwangyang-aengmi 12) of weedy rice. This study was conducted to investigate whether unintentional alterations in phenotypic characteristics occurred in the transgenic rice and whether the altered traits were similar to those in the two weedy rices. All qualitative traits studied were similar in the transgenic or wild-type rice. On the other hand, awn presence, flag leaf attitude and grain color differed considerably between herbicide-tolerant transgenic rice and weedy rice. As for quantitative traits, plant height, the number of tillers per plant and shoot dry weight were significantly greater for weedy rice than transgenic or wild-type rice. Grain weight per plant and 1000-grain weight of transgenic (or wild-type) rice were significantly greater than those of weedy rice. Transgenic rice shattered less than the other rices. Amylose and protein contents in embryos of transgenic rice were significantly different from those of weedy rice. The potential for weediness of the transgenic rice may be assessed using phenotype comparison between transgenic and weedy rice as shown in this study.

• Weed & Turfgrass Science
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• v.3 no.4
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• pp.312-317
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• 2014

This study was conducted to obtain basis information for effective weed control by the fact-finding survey of herbicides use at farmer's level and distribution of herbicide resistant weeds in paddy field of Jeonbuk province, Korea. The distributions of major paddy field weeds and frequently used herbicide according to the survey were as follows. The dominant weeds in rice paddy field were Echinochloa crus-galli, Eleocharis kuroguwai, Scirpus juncoides, Monochoria vaginalis, etc.. Preferred herbicides widely used by farmers were ranked in the following order, early and middle treatment (48.0%), treatment before transplanting (36.7%) and foliar treatment (15.3%). The occurrence of herbicide-resistant weeds according to collected paddy soils was as follows. The occurring area of herbicide-resistant weeds was 24,413 ha, approximately 18.4% of rice cultivation area. Herbicide-resistant weeds were occurred in four species. The order of occurrence were Scirpus juncoides (39.0%) > Monochoria vaginalis (27.8%) > Echinochloa crus-galli (16.6%) and Cyperus difformis (16.6%). This information could be useful for estimation of future herbicide-resistant weed and establishment of herbicide-resistant weed control methods in Jeonbuk province, Korea.

• Korean Journal of Weed Science
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• v.12 no.3
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• pp.223-229
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• 1992

Very recently, the cultural pattern of paddy rice in Korea was transitted in a short period, and resulted as earlier in season and more in fertillizer application among others. Specially the weed emergence in paddy fields was drastically increased as affected by change of cultural pattern into early planting and into direct seeding methods. Of course, the direct-seeding in row seeding induced more weeds than in broad-cast direct -seeding. By maintaining the water level with saturation of the paddy surface induced more weeds, relatively more annual weeds than by deep in water level, respectively. Relatively more annuals in number of species and in emerged quantity comparing with perennials was caused by the shifting of cultural methods from transplanting to direct seeding. The severe weed competition damages were mainly resulted due to the shading by taller plant heights of weeds than crop during the whole growing seasons. Conclusively, accepting of direct seeding methods in paddy rice culture in Korea, the present bases for weed control methods ought to be naturally and effectively improved to meet the newly made weed problems.

• Korean Journal of Weed Science
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• v.5 no.1
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• pp.24-34
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• 1985

To estimate the fundamental situation of weed emergence and it's competition to paddy rice (critical competition period and threshold level) in the southern paddy area in Korea, two rice cultivars (Pungsanbyo and Tongjinbyo) under two cropping periods (Mono- and After-barley-cropping) were experimented. As a result, the dominant weed species (Monochoria vaginalis and Scirpus juncoides Roxb.) and the better emerging conditions (rather at the monocropping and cv. Punsanbyo) were identified. Also, the main components of yield decrease (25-55% of the weed-free check) of both cultivars as affected by weed competition were the number of spikelets, panicle and ripening rate in monocropping, and the ripening rate and grain weight in after-barley-cropping, respectively. Under the situation of combinated dominance with Monochoria v. and Scirpus j. among others, the duration of critical competition periods was enlarged.

• Weed & Turfgrass Science
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• v.4 no.3
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• pp.151-158
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• 2015

This study was conducted to establish the effective weed management methods in rice field simultaneously dominated by the herbicide resistant Echinochloa oryzicola, Monochoria vaginalis and Scirpus juncoides. Herbicides registered for use before transplanting, oxadiazon 12% EC, pyrazolate 36% SC, pretilachlor 14% EC and thiobencarb 50% EC were effective until 0.5 leaf stage of herbicide resistant Echinochloa oryzoides. Herbicides registered for use after transplanting, fentrazamide 1% GR and mefenacet 18% SC were effective until 2 leaf stage of herbicide resistant Echinochloa oryzicola and triafamone 0.98% SC was possible to control up to 4 leaf stage. HPPD inhibitors, benzobicyclon, mesotrione and tefuryltrione SC, were simultaneously effective to SU herbicide-resistant Monochoria vaginalis and Scirpus juncoides. Herbicides registered for use before transplanting, benzobicyclon + oxadiargyl EC out of the tested herbicide was most effective in rice field simultaneously dominated by the herbicide resistant Echinochloa oryzicola, Monochoria vaginalis and Scirpus juncoides. Its effectiveness rises in proportion to flooding duration. Mazosulfuron GR, a herbicides registered for use after transplanting was most effective without phytotoxicity until 60 days after transplanting in rice field simultaneously dominated by the herbicide resistant Echinochloa oryzicola.