• Korean Journal of Weed Science
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• v.12 no.3
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• pp.230-260
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• 1992

The paper was reviewed the research results on weed dynamics and effective control methods in direct-seeded rice crop. Direct seeding method resulted in drastic increment of weed growth compared to transplanting method and also changed in troublesome weed flora. Two to three fold more weeds were harvested at the direct seeded rice and weed flora of dominant species shifted toward $C_4$type grass weeds. Some of the important troublesome weeds in direct seeded rice were Echinochloa crus-galle, Oryza saliva ssp spontanea, Leptochloa chinensis. Setaria viridus. Digitaria adsendens, Sesbania exaltata, Aeschynomene indica, Algae, etc. Yield loss due to weed competiton was about 40-60% for water-seeded and about 70-100% for dry-seeded rice while these for transplanted rice were about 25-35% for mechanical transplanting and about 10-20% for manual transplanting, respectively. Integrated weed management concept was neede to approach weed control effectively. Several cultural technologies were very effective to suppress the weed growth. These were tillage operation, water management, seeding date and seeding rate. Crop residues of barley, rice, wheat, oat and italian ryegrass were also effectivly suppressed the paddy weeds particularly to Potamogeton distiuctus, a perennial broadleaf weed. A pathogen of Epicoccosorus nematosporus identified from Eleocharis kuroguwai was an excellent potential bioagent to control the most troublesome perennial sedge weed of E. Kuroguwai without arising any detrimental effect. The herbicidal efficacy of this pathogen was as high as bentazon herbicide. Plant growth regulator of paclobutrazol (pp-333) was another possible alternative to reduce the herbicide use. In current, herbicide exhibited the most conspicuous results to control weeds in direct-seeded rice even though the application technologies were not fully established. Recommendations for herbicide application were suggested for in both water-and dry-seeded rice in USA, Japan and Korea, respectively. To make better and comprehensive recommendations further studies on weed ecology and herbicide development were emphasized.

• Weed & Turfgrass Science
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• v.3 no.3
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• pp.174-182
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• 2014

This paper provides some of the scientific background on how projected environmental conditions could affect weeds and weed management in crops. Elevated $CO_2$ levels may have positive effects on crop competitiveness with $C_4$ weeds, but these are generally outnumbered by $C_3$ species in weed populations. Moreover, higher temperatures and drought will favor $C_4$ over $C_3$ plants. The implementation of climate change adaptation technologies, such as drought-tolerant germplasm and water-saving irrigation regimes, will have consequences for crop-weed competition. Rainfed production systems are thought to be most vulnerable to the direct effects of climate change and are likely to face increased competition from $C_4$ and parasitic weeds. Biotic stress-tolerant crop cultivars to be developed for these systems should encompass weed competitiveness and parasitic-weed resistance. In irrigated systems, indirect effects will be more important and weed management strategies should be diversified to lessen dependency on herbicides and mechanical control, and be targeted to perennial rhizomatous ($C_3$) weeds. Water-saving production methods that replace a weed-suppressive floodwater layer by intermittent or continuous periods of aerobic conditions necessitate additional weed management strategies to address the inherent increases in weed competition. Thus, climatic conditions have a great effect on weed population dynamics all over the world.

• Asian Journal of Turfgrass Science
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• v.21 no.1
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• pp.69-79
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• 2007

Incorporating herbicides application into a fertilization program has several benefits including saving time and reducing traffics on the lawn. Premixed products of fertilizers and herbicides are commonly known as Weed & Feed in the lawn-care industry. To compare Weed & Feed with separate applications of fertilizers and herbicides on a Kentucky bluegrass (Poa pratensis L.) lawn, a Weed & Feed 28-3-3, containing 0.64% 2,4-D, 0.31% MCPP, and 0.03% dicamba of active ingredients, was used in this study. The first application was in May, with the second in June or Sept. Herbicides in forms of 2,4-D (LV-4, 4EC), MCPP (4EC), and dicamba (Clarity, 4EC) were applied at rates equal to the amounts in Weed & Feed or at half of the rates. The dominant weed in both locations was common dandelion (Taraxacum officinale Weber.) in 2005 and 2004. A secondary weed was Canada thistle (Cirsium arvense (L.) Scop.) in 2004 and broadleaf plantain (Plantago major L.) in 2005. When applied in May and June, fertilizer plus full rate of herbicides treatment achieved 112.3 and 83.7 days of acceptable turf quality in 2004 and 2005, respectively. During the same period, Weed & Feed resulted in 58.7 and 24.3 days of acceptable turf quality, respectively. Our study showed that Weed & Feed was generally as effective in weed control as the same amount of fertilizer plus half rates of herbicides sprayed although results may vary due to the timing of application. Fertilizer plus full rates of herbicides provided the same or better results of weed control than Weed & Feed.

• Spatial Information Research
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• v.11 no.1
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• pp.23-32
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• 2003

TIN is applied in pondage calculation and topography analysis. And much processing time and storage capacity are needed because TIN contains information as elevation, slope and aspect. In the construction of TIN using contour, weed tolerance that is used for the simplification of line is influenced on the sampling distance of contour. The processing time and storage capacity of TIN are calculated in according to the weed tolerance of various size in this research. And we estimated OEMs standard error that is created from TIN to present reasonable weed tolerance and decided the size of weed tolerance that satisfy DEM standard error. We got TINs weed tolerance that satisfy DEM standard error(5m) was 70m and DEMs resolution is 20m as estimation result.

• Korean Journal of Weed Science
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• v.17 no.1
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• pp.124-134
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• 1997

As control of plant diseases, insects and weeds were heavily relied on pesticides, residues of pesticides in environment and food supply were recently focused by environmentalists and consumer groups. The reduction of pesticide use was implemented in Sweden, Denmark, Netherland, England, and United States. Therefore, it is very important to discuss environmentally sound systems of weed management including cultural, mechanical, and integrated weed control. Mechanical methods using tillage, cultivation, mulching, burning, mowing, solarization, and UHF are used as one of most effective environmentally sound weed management systems. Cultural practices favoring the crops are excellent weed management measures. Correct seedbed preparation for the soil and cultural system, and use competitive cultivars contribute to weed management. Increasing crop density by higher seeding rate or by narrowing row width and careful attention to optimum fertility to produce vigorous crop plants increase competitiveness of crops against weeds. Crop rotation breaks life cycles of weeds by alternating the crop it must associate with. Herbicides are efficient and profitable to control weeds, but must be part of a total weed management program with use of minimum rate. The best weed management will be an integrated approach including two or more methods to manage weed problems.

• Korean Journal of Weed Science
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• v.18 no.4
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• pp.364-370
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• 1998

A weed population has been mainly analyzed through vegetative analysis method in ecology. However, this method is difficult to understand a detailed feature of weed dominance in terms of region and a particular weed species. Since GIS(Geographic Information System) tool has been introduced, this constraint was able to be solved. GIS analysis for the nationwide weed survey data in 1981 revealed that most predominant weed was Monochoria vaginalis and this species predominated mostly in a western part of Chungnam, a part of Kyunggi, a northern and southern part of Kyungbuk province of Korea. Eleocharis kuroguwai which was the most predominant weed species in 1992 was occurred at southern part of Kyunggi, central and western parts of Chungnam, and southern western part of Chumnam at the GIS analysis. GIS analysis was proven to give much more detailed information than vegetative analysis of weed population and this means that a data analysis by GIS would be used for operating a high effective control strategy against target weed species and site.

• Korean Journal of Weed Science
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• v.18 no.4
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• pp.356-363
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• 1998

In general weed vegetation analysis has been applied to the study of weed population shift. However, it is a limited tool for understanding a problem region and a specific weed species in a certain area. Recently GIS may be used as an important tool to solve this target or to conduct specific field analysis which enables to introduce a reasonable management strategy. Thus, the GIS study was carried out to understand an integrated weed population changes between 1981 and 1992 in Korea. The nationwide weed survey was performed through the whole rice paddy fields in 1981 and 1992. Weed occurrence was totally different over whole country based on these data. In 1981 a region with high weed occurrence was at western and central areas of Korea in terms of weed population density but this was changed into western and southern area in 1992. In both years there were high weed population density at Taean, Seosan county of Chungnam province in Korea. Thus, this particular area may be needed to introduce a special strategy to reduce weed population density and/or to control problem weed species.

• Korean Journal of Weed Science
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• v.1 no.1
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• pp.5-14
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• 1981

Weed is one of the problems in the crop land as well as in uncultivated land, raising the farm management costs. Therefore, the weed control is essential for effective agricultural management. The cost for weed control in Korea occupies on the average 27.6% of the total labor cost required. Agricultural policies since 1960 were transferring from yield increase due to land productivities to increase of income due to labor productivities. Therefore, the weed control by hand is also changed to weed control by chemicals. The weed control by chemicals has also brought about some side-effects and needs better, improved weed control methods. The present weed control situation and related problems were studied to present new approaches for agricultural development in the future. There were 458 species of weeds in 82 families which were growing in the crop land. The weeds to control, however, are 12 in paddy field and 9 in upland. So far weeds in paddy field are well under control, while weeds in upland are poorly controlled due to change in chemical efficiency and chemical damage in the upland. The administration, research and extension work for the efficient use of agricultural chemicals have been done by various institutions, such as Office of Rural Development, Office of Forestry, and chemical companies. The courses for agricultural chemicals were offered in the agricultural colleges. However, the efficiency of chemicals could not be maximized due to the poor relationships among related institutes. The newly established Agricultural Chemical Research Center at the Office of Rural Development and the Korean Weed Science Association are expected to contribute toward improving weed control in Korea. The Korean agriculture in the future will eventually be mechanized and the varieties resistant to high nitrogen application and to high plant density will be required for high yields. The rice will be transplanted earlier and the whole growing period will be extended. The application of organic matter will be increased for increasing soil fertility, and the use of agricultural chemicals will be continued. Under such a condition, the studies on the weed occurrence and its integrated control measures will be needed. Also weed controls in the newly exclaimed land, crop varieties, horticultural varieties, forage crops, and forests are also needed to study. Basic and practical researches for the weed control to improve the labor productivity will be also needed. In order to meet the all requirements for efficient weed control, weed control systems including all the academics, research and extension workers, administratives, farmers and companies should be established. Also securing researchers and education of personnels are pre-required and research funds for the chemical studies should be provided efficiently and timely.

• Weed & Turfgrass Science
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• v.4 no.3
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• pp.199-208
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• 2015

This study was conducted to provide basic information for weed control by surveying the occurrence of weed species in upland crop fields in Gyeongnam province of Korea. The result of this survey, 55 weed species 21 families in barley fields, 56 weed species 22 families in garlic fields, 47 weed species 19 families in onion fields, 68 weed species 26 families in Chinese cabbage fields, 54 weed species 22 families in potato fields, 62 weed species 25 families in sweet potato fields, 87 weed species 29 families in red pepper fields, 79 weed species 28 families in corn fields, 84 weed species 29 families in soybean fields. The most dominant weed species in upland crop fields of Gyeongnam province were Alopecurus aequalis var. amurensis 20.7% (barley fields), Cardamine flexuosa 12.3% (garlic fields), Chenopodium ficifolium 18.7% (onion fields), Portulaca oleracea 8.1% (Chinese cabbage fields), Chenopodium ficifolium 13% (potato fields), Digitaria ciliaris 12.6% (sweet potato fields and red pepper fields) and Digitaria ciliaris 11.3% (corn fields), 13.2% (soybean fields). This information could be useful for establishment of future weed control methods in Gyeongnam province.

• Journal of Ecology and Environment
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• v.38 no.3
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• pp.353-360
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• 2015

A survey of weed occurrence was conducted to identify problematic weed species in a horticultural crop field to get basic information for effective weed control. Surveys of weed species occurring in horticultural crop fields (garlic, onion, red pepper and Chinese cabbage) were conducted in Chungnam province of Korea from April to October in 2014. A total of 516 sites of the 17 regions were identified as having 114 weed species belonging to 32 families. The most dominant weed species in the horticultural crop fields were Chenopodium album var. centrorubrum (8.83%), followed by Digitaria ciliaris (5.71%), Conyza canadensis (5.46%) and Capsella bursa-pastoris (4.67%). Specifically, as a result of this study, the occurrence of 35 species of exotic weeds, such as Chenopodium album and Taraxacum officinale, were confirmed. Almost 68% of the investigation sites was determined under dominance value 1 (range of cover < 10; numerous individuals) by Braun-Branquet cover-abundance scale, indicating a proper weed control in horticultural crop field. As a result of scientific and technological advances, an improved cultivation method is changing the weed occurrence in agricultural land. Additional research needs to be undertaken for the development of weed control methods through such periodic monitoring of occurrence of weeds.