• 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.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.3
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• pp.221-224
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• 1999

A field experiment was carried out to observe the weed control effects of vetch and to evaluate vetch characteristics on clay loam soil in no-till direct-sown rice-vetch cropping systems. The effects of weed control, forage productivity, and N content of vetch plants were investigated. With the progress of plant growth, density of Chinese milk vetch (Astragalus sinicus L.) gradually decreased, but densities of foxtail and other weeds decreased steeply due to the depression by the over-shaded vetch canopy in a no-till direct-sown rice-vetch cropping paddy field. The vetch density in tillage systems was lower than in notillage cropping systems. Lower vetch density occurred with an increase in foxtail density and other weeds. Weed control effect increased by the progress of vetch growth, which indicated that the vetch canopy over-shaded the weeds. Vetch straw was degraded rapidly submergence after with water at the time of wet sowing of rice. Early harvesting of vetch seed resulted in lower seed germination. To acquire enough seedlings without re-sowing, the harvesting of seed should be delayed at least 28 days after the flowering stage in order to ensure the vetch population is sustainable in a no-till direct-sown rice-vetch cropping system. In order to improve the survival of vetch plants, vetch seeds should germinate from the heading .stage to before the full-ripening stage of rice plants. To enhance the percent of over-wintering survival, vetch seeds should germinate no later than the end of October in southern Korea. The dry weight of vetch plants increased with the progress of vetch growth until the flowering stage but N content decreased for 30 days from before the flowering stage (2.9%) until the ripening stage (1.8%). We concluded that Chinese milk vetch could have an effect on weed control before the flowering stage, sustainability without re-sowing of seed annually, and effective green manure for rice pre-crop in no-till direct-sown rice-vetch relay cropping systems.

• Korean Journal of Weed Science
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• v.17 no.1
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• pp.1-9
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• 1997

The survey of weed community in paddy field was carried out to investigate the changes of weed species on 340 fields in Kyonggi Area in 1995, that is almost same condition as sampled in 1991. The weed species observed include 3 species of grasses, 5 species of sedges and 14 species of broadleaf and other weed. Herbicide treatment system in one time treatment vs more than two time treatment was 34:66 percentage. About 25 percentage among one time treatment system was used butachlor G. Ratio of annual weed vs perennial weed was 38:62, and then perennial weed ratio was high. Major dominant weed species were Sagitaria trifolia, Eleocharis kuroguwai, Echinochloa crus-galli, Bidens tripartita and Monochoria vaginalis. Weed occurrence was decreased as order of normal soil, poorly drained soil and saline soil. Dormant weed species were S. trifolia, E. kuroguwai, E. crus-galli and B. tripartita in normal soil and were S. trifolia, E. kuroguwai, E. crus-galli and Polygonium hydropiper in poorly drained soil, and were Scirpus planiculmis, S. trifolia and E. kuroguwai in saline soil. Weed occurrence was increased with delaying the transplanting time; dominant weed species were S. trifolia, E. kuroguwai, E. crus-galli and M. vaginalis in May transplanting field and were E. kuroguwai, S. trifolia, and C. serotinus in June transplanting field. Weed occurrence was decreased as order of non-plowing transplanting field, autumn plowing and spring plowing paddy field. Dominant weed species were S. trifolia, E. kuroguwai, E. crus-galli and M. vaginalis in autumn plowing, were S. trifolia, E. kuroguwai, E. crus-galli and B. tripartita in spring plowing, and were E. crus-galli, S. hotarui and S. trifolia in non-plowing transplanting field.

• Journal of The Korean Society of Grassland and Forage Science
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• v.28 no.4
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• pp.307-314
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• 2008

No comprehensive tillage system of corn (Zea mays L.) has been conducted in Korea. Therefore, this experiment was carried to determine soil characteristics, weed and forage production in tillage system of corn. Plot was allotted to one of four treatments in a randomized block design using tillage system. The four treatments were (T1) conventional tillage, plow and rotary till, (T2) rotary till, (T3) disk till, and (T4) no-till system. In soil characteristics before planting and after harvest of corn, pH and organic matter at planting date was higher than at harvest date, however, there were no difference among tillage system. Days from planting to silking of no-till was the longest among tillage system. Lodging resistance of disk and no-till were higher than conventional and rotary till due to its thicken stem diameter. Main weed in corn field are barnyard grass (Echinochloa crusgall), velvetleaf(Abutilon avicennae), crabgrass (Digitatia saguinalis), and redroot pigweed (Amaranthus retroflexus). Weed population was lower in no-till than others tillage system. Dry matter (DM) content and ear percentage of conventional and rotary till were higher than others in corn field. However, DM and total digestible nutrients (TDN) yields of disk and no-till were higher than those of conventional and rotary till. Therefore, disk and no-till are more suitable in corn silage system because of high lodging resistance and forage yield, and low weed population.

• Current Research on Agriculture and Life Sciences
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• v.4
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• pp.22-26
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• 1986

This study was conducted to investigate weed population dynamic in orchard and to establish an appropriate application time for oxyfluorfen. 28 weed species including Persicaria hydropiper was observed to be problem weeds in orchard. P. hydropiper was on single dominant species which increased importance value of 13.7 on May 15 to 60.79 on August 10, followed by Calystegia hederacea, Alopecurus aequalis, Capsella bursa-pastoris, Roripa islandica, Echinochloa crus-galli, Potulaca olearcea, Elusin indica. Simpson's index increase from 0.11 on May 1 to 0.40 of August 10, indicating the dominance of specific weed species. The effective herbicide to control these weeds was oxyfluorfen at 5kg prod./ha applied at pereemergence treatment on March 25, showing more than 90% control for 120 days after application. Preemergence application of oxyfluorfen at 3kg prod./ha on March 25 followed by paraquat 3kg prod./ha applied on June 25 as the foliar application can maintain the clean orchard for a year, showing on of the promising and applicable control system. The most appropriate rate and time for oxyfluorfen seemed to be 5kg prod./ha applied on March 25.

• Korean journal of applied entomology
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• v.61 no.1
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• pp.255-266
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• 2022

This study was conducted to examine the effects of grass vegetation (W: manual weeding, NW: herbicide sprays) and pyrethroid spray (P: pyrethroid spray, NP: no pyrethroid spray) on the population dynamics of Panonychus citri and natural enemies in citrus orchards. Two essential hypothesis were made to test the population dynamics: 1) weed planting promotes natural enemies by offering habitat and alternative food sources, resulting in the reduction of P. citri populations, and 2) pyrethroid spray removes natural enemies by its non-selective toxicity, resulting in the increasement of P. citri populations. The observed natural enemy populations (mainly Phytoseiids and Agistemus sp.) were not different largely from the expected values in the hypothesis, which assumes more abundant natural enemies in weeds and no pyrethroid plots. Although some discrepancy was occurred in NW+NP and W+NP plots in 2011, the observed values were almost same with expected values in 2012. In overall, pesticide effect was strongly significant and pyrthroids removed largely natural enemies. Although habitat (weeds) effect showed a conflict result, natural enemy population increased in plots allowing weed growth, when considering the increased autumn population relatively compared to that of spring-summer population. The decreased abnormal P. citri populations in pyrethroid plots could be explained under the assumption of a strong repellent behavior of P. citri to the pyrethroids.

• Weed & Turfgrass Science
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• v.3 no.4
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• pp.292-298
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• 2014

Purple ammannia (Ammannia coccinea Rottb.) is an exotic weed originated from North America. It was known to be a noxious weed in a rice paddy field for the competition with rice. We investigated its distribution and habitat types in Korea to obtain basic data for the management plan of this species. Although purple ammannia is currently not a dominant species in natural habitats, its nationwide distribution was found in our study. We categorized the types of its habitats as margins of rice paddies, abandoned paddy fields, riverine wetlands and reservoirs. Particularly, purple ammannia plants were frequently located along banks of irrigation channels that ran through rice paddies and surrounding wetlands. Because they mainly occurred along the direction of water flow, we considered that the plants have spread along water courses. A total of 69 vascular plant taxa was identified at the habitats of purple ammannia. The largest group of life form among purple ammannia population was therophytes, which indicates that purple ammannia mostly grow in the disturbed habitats.

• Proceedings of the Korean Society for Information Management Conference
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• 2000.08a
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• pp.129-132
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• 2000

GIS(Geographic Information System) tool has been applied to determine a spatial difference of weed population density in paddy field and it has introduced to rice yield difference among counties as well as to rice blast in Korea. There was highly difference between sampling sites in terms of spatial analysis which may imply to be able to apply this tool for the precesion agriculture in the 21 century.

• Weed & Turfgrass Science
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• v.6 no.2
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• pp.86-108
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• 2017

The nationwide weed survey was conducted in arable land, paddy field, upland, orchard and pasture, over whole country of Korea during 3 years from 2013 to 2015. Also, these survey were conducted in order to determine a change of weed community and to identify a major dominant weed species, and problem weeds. Weeds of arable land were composed of 619 species belonging to 81 families. Weeds occurred in paddy field were 90 species belonging to 28 families, upland weeds were 375 species of 50 families, orchard weeds were 492 species of 63 families and pasture weeds 275 species of 52 families. Among total 81 families, the Asteraceae (15.5%) was the biggest family, followed by Poaceae (13.1%), Fabaceae (5.5%), Cyperaceae (5.2%), Polygonaceae (6.3%), respectively. And these weed species were composed of annual weeds of 209 species (33.8%), winter annual of 102 species (16.4%) and perennial weeds of 308 species (49.8%). Exotic weeds naturalized in Korea were investigated as 166 species. Weed flora in Korean cultivation area have been increased as much as 13 families and 186 species for 10 years compared to 2000~2004 weed survey result of 68 families and 433 species. The increment could be resulted from the change of weed population such as increase of the herbicide-resistant and the difference of investigation method.

• Korean Journal of Weed Science
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• v.31 no.1
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• pp.41-48
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• 2011

This survey of weed population by different soil moisture with paddy-upland rotation was conducted to investigate information on weed flora and its ecology between two years. Weed species were assessed in April : 2009, 2010. Soil samples were taken from each study plot to assess the impact soil moisture on the occurrence and abundance of dominance weed species. Soil water of poorly drained field ranged from 10.2~18.2% more than 11.8~14.3% of somewhat poorly drained field. Weeds of fields composed of 19 species belonging to 12 families. Among 12 families, 6 weed species belonged to Compositae (31.6%) were the biggest family, Cruciferae were 2 species (10.5%), and Rubiaceae were 2 species (10.5%), respectively. Youngia japonica had the highest summed dominance ratio(SDR) (97.0%) and followed by Conyza canadensis (92.1%), Galium spurium (35.3%) and Hemistepta lyrata (28.4%) of somewhat poorly drainage in 2009. Artemisia princeps the highest SDR (100%) and followed by Stellaria alsine(55.2%), Y. japonica (38.3%) and Nasturtium officinale (28.5%) of poorly drainage in 2009. And, Stellaria alsine had the highest SDR (86.8%) and followed by Alopecurus aequalis (77.7%), Astragalus sinicus (68.7%) and Y. japonica (46.3%) of somewhat poorly drainage in 2010. S. alsine the highest SDR (93.7%) and followed by A. aequalis (78.6%), Nasturtium officinale (31.3%) and Y. japonica (30.4%) of poorly drainage in 2010. Simpson's index was calculated to 0.12~0.23, which showed that weed occurrence with different soil moisture in paddy-upland rotation and between years was various. Similarity coefficient between years was 43.0% (2009) and 74.2% (2010), which indicate a low diversity because of the moisture in the agro-ecosystem.