• Korean Journal of Weed Science
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• v.30 no.2
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• pp.171-176
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• 2010

Vicia angustifolia L. is native plant of winter annual leguminous weed in Korea. Objective of this research was to investigate the effects of V. angustifolia as green manure for rice production in sustainable agriculture. Seed size of V. angustifolia was smaller than that hairy vetch as control plant, while seed number in same amount was approximately 1.4-fold higher. V. angustifolia started stem elongation in early April. In addition, flowering and dead-ripe stages of the plant reached at May $5^{th}$ and June $1^{st}$, respectively. Growth of V. angustifolia-barley mixed cropping system in upland was promoted up to 101 cm of plant length compared to 46.6 to 60.9 cm that grown in paddy. Biomass yield of V. angustifolia was 14.5 kg $ha^{-1}$ in single cropping system of paddy soil, and the amount of nitrogen was 65 kg $ha^{-1}$. Moreover, self-reseedling of fallen seed from V. angustifolia grown in previous year in paddy soil was significantly higher than that hairy vetch plant. These results suggested that V. angustifolia can be uses as green manure in addition to reducing the mineral fertilizer application in rice production for sustainable agriculture.

• Korean Journal of Weed Science
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• v.7 no.1
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• pp.12-18
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• 1987

Seed dormancy and germination responses to light and gases were determined for Echinochloa colona (L.) Link. E. colons seeds did not require a period of after-ripening for breaking dormancy. Water movement occurred readily across the seed coat. Repeated cycles of hydration and dehydration reduced viability and thence germination. Water imbibition for 24 h increased seed moisture by 21%; seeds returned to their original weight after drying at room temperature for 13 h. Removal of seed-coats increased germination in the dark. Light stimulated germination. Germination at a daylight intensity of 51.9 $Wm^{-2}$ or less was significantly reduced. Germination of seeds which were exposed to light for 1 h each day was significantly less than that of seeds exposed for longer than 2 h a day. Seeds subjected to blue light had delayed and decreased germination compared to seeds exposed to red light. Ethylene or carbon dioxide exogenenously added in the presence of light stimulated germination. The addition of the two gases together had a synergistic effect. In the dark, however, the two gases did not increase germination.

• Korean Journal of Weed Science
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• v.7 no.1
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• pp.45-51
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• 1987

This experiment was conducted to find out the critical competitive period and competitive ability of rice against red rice. Plant height and number of tillers of rice decreased as red rice competed with rice during active tillering stage. The maximum tillering stage of rice competed with red rice became about 10days earlier than those non-competed. Significant yield reduction of rice was observed in the plots competed for 20 days after transplating or longer. Such a yield reduction can be mainly attributed to the decrease in number of panicles per hill and grain number per panicle. In a replacement diagram for rice and red rice, their competition is turned out being antagonized. The relative yield total was considered lower than 1. Grain number, culm and panicle length of rice was not affected significantly by inter-specific competition. Rice grain yield reduction was highly correlated with the number of panicles of red rice. Three hundred panicles/$m^2$ of the red rice were necessary to reduce rice grain yield by 50% of the check plot.

• Korean Journal of Weed Science
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• v.8 no.1
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• pp.23-27
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• 1988

This experiment was conducted to determine germination ability, life cycle, regrowth ability of Portulaca oleracea L. The newly harvested seeds from P. oleracea flowered before July 15 were able to germinate, but percent germination decreased markedly as the flowering time was later than July 15, showing no germination of seed collected at Sept. 12 which were flowered at August 30, 76.5% of seeds can be germinated in the light as seed stored in room condition for 90 days, but in dark condition, it needed 2 years of seed storage for germination. Low temperature treatment at $2^{\circ}C$ for 5 days enhanced seed germination of P. oleracea in both light and dark conditions. The maximum vagetative growth was observed at 30 to 75 days after seeding. The late seeding time such as July 1 shortened the period of vegetative growth. However, regardless of the seeding times, the first flowering was observed at about 40 days after seeding. Leaf numbers, shoot lengths, fresh and dry weights were greatly affected by the seeding dates, showing that the earlier seedings produced significantly higher shoot length, fresh and dry weight, leaf numbers and branch numbers than those of the late seedings. When all branches were removed on 68 days after seeding, their regrowth ability was 50.3% and cuttaged branches showed 78.1% regrowth as compared to intact plant.

• Korean Journal of Weed Science
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• v.12 no.2
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• pp.173-182
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• 1992

Regardless of the test species, germination was adversely affected by the different concentrations of the acidic and neutral fractions of sunflower root exudates while the basic and aqueous fractions had no effect on germination. In both test species, root lengths were inhibited slightly more than shoot lengths. Significant reduction in fresh weights of the test species was observed when the test species were treated with the acidic and neutral fractions but not with the basic and aqueous fractions. Six compounds, hydroquinone, ${\beta}$-resorcyclic acid, vanillic acid, caffeic acid, salicylic acid, and quercetin, were characterized from the acidic fraction. Seven compounds, hydroquinone, gentisic acid, ${\beta}$-resorcyclic acid, vanillic acid, caffeic acid, ferulic acid, and quercetin, were elucidated from the neutral fraction.

• Korean Journal of Weed Science
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• v.13 no.1
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• pp.7-13
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• 1993

Experiments were carried out to investigate the utilization of paraquat and diquat as desiccants for harvest-aid of sesame. When paraquat and diquat were sprayed at 3days or 3hours before cutting of sesame plants, moisture content in treated plots was evenly rapidly decreased and sesame yeild was not significantly different as compared with that in untreated plot. Percentage of germination of sesame seed in treated plots was similar to that in untreated check. Residual amount in sesame seed was not detectable when these chemicals were treated with 250ppm at 3days before cutting of sesame plant. Percentage of thrashing was high in sesame plants treated with paraquat and diauat with the lapse of time after cutting. Required labor in thrashing of sesame was reduced when applied with these chemicals. Harvest efficiency of sesame after spray of paraquat and diquat was good by comparison with the traditional practice.

• Korean Journal of Weed Science
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• v.31 no.4
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• pp.368-374
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• 2011

This experiment was conducted to Investigate the herbicidal activity of naturally developed d-Limonene on the control of Sicyos angulatus L. which is destructive to biodiversity and ecosystem under greenhouse and open field condition. Among the tested concentrations, most efficacy of early foliar application(leaf stage with 1.5 and 3) of d-Limonene was found in $70mg\;mL^{-1}$, followed by $35mg\;mL^{-1}$, $17.5mg\;mL^{-1}$ in that order under greenhouse condition. The higher the d-Limonene concentration, the better the effect in greenhouse condition. In leaf stage with 2, 3 and 5 under open field condition, the higher the d-Limonene concentrations, the higher the weeding effect. The remarkable effect was, particularly, found in d-Limonene with $70mg\;mL^{-1}$ while little was found in the plants with d-Limonene with $35mg\;mL^{-1}$. In the case of 15 leaf stage of S. angulatus L. treated with d-Limonene under outside treatment effect was low. The treatment effect of d-Limonene under open field compared with greenhouse condition was more significant. It can be recommended that d-Limonene with $70mg\;mL^{-1}$ could control S. angulatus L. by 5 leaf stage.

• Korean Journal of Weed Science
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• v.31 no.1
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• pp.112-117
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• 2011

A series of experiments was conducted to investigate the herbicidal activity of natural compound chrysophanic acid under the greenhouse condition in 16 weed species. Chrysophanic acid showed non-selective herbicidal activity. While chrysophanic acid exhibited severe injury by foliar treatment, little or no injury was found by the soil treatment. Among the tested weeds, the most effective activity was found in grass and broad leaf weeds, a lower significant difference in herbicidal activity was found in sedge. At early post-emergence, weeds appeared to be very susceptible to chrysophanic acid with $2,000{\mu}g\;mL^{-1}$. The higher the natural compound concentrations, the lower weed growth. At middle post-emergence, weeds appeared to be very effective to chrysophanic acid with $30,000{\mu}g\;mL^{-1}$.

• Korean Journal of Soil Science and Fertilizer
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• v.28 no.2
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• pp.114-122
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• 1995

Complexation experiment between humic acid and heavy metal cations was conducted to clear information on heavy metal adsorption by soil organic constituent. The absorbance of UV-visible light of humic acid-metal complexes increased with increasing wavelength, and the order of their absorbance was in the order of Zn->Cd->Cu- saturated humic acid. Carboxyl and phenolic OH groups participated in the complex formation between heavy metal cations and functional groups of humic acid, and the amounts complex was in the order of $Cu^{+{+}}$ > $Zn^{+{+}}$ $\geq$ $Cd^{+{+}}$. The stability constants of humic acid-metal complexes increased with increasing pH, and the order of first stability constants was $Zn^{+{+}}$ > $Cd^{+{+}}$ > $Cu^{+{+}}$, and those of second and overall stability constants were $Cu^{+{+}}$ > $Zn^{+{+}}$ > $Cd^{+{+}}$. With increasing pH, the average binding numbers betwen heavy metal cations and functional groups of humic acid increased the order of $Cu^{+{+}}$ > $Zn^{+{+}}$ > $Cd^{+{+}}$. It was postulated that two types of complexations between heavy metal cations and functional groups of humic acid. One was the reactions in which only carboxyl groups participated to form complexes, and the other was those in which both carboxyl and phenolic OH groups simultaneously participated.

• Korean Journal of Weed Science
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• v.5 no.2
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• pp.175-186
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• 1985

Research situation and recent research activities of the RDA of Korea were reviewed and summarized for rice nurserybed. Sixty five percent of total 784 weed research items were carried out as rice research while only 6 percent was belonged to nurserybed within rice research. The floristic composition based on the degree of dominance significantly affected by herbicide properties, type of nurserybed and seeding itself. Herbicidal phytotoxicity of currently used several herbicides was greatly dependent upon the covering, absorption, germination, and irrigation regimes. The new safening agent "CGA 123 407" (4,6-dichloro-2-phenyl-pyrimidine) permited the safe application of pretilachlor (2-chloro-2',6-diethyl-N-(2-propoxyethyl) acetanilide) as a pre-emergence herbicide without reducing herbicidal efficacy. Several new herbicides, pyrazolate (4-(2,4-dichlorobenzoyl)-1,3-dimethylpyrazol-5-yl-p-toluenesulphonate), SL-49 (1,3-dimethyl-4-(2,4-dichlorobenzoyl)-5-phenacyloxy-pyrazole) MY-93 (S(1-methyl-1-phenethyl)-piperidine-1-carbathioate) and DPX-84 ((methyl 2- ((4,6-dimethoxypyrimidin-2-yl) amino-carbonyl) aminosulfonylmethyl)) benzolate)) performed satisfactorily in terms of safety and herbicidal efficacy for both surface covered and surface pressed nurserybed after herbicide application and thus expected very significant contributions not only for all kind of nurserybeds but also for direct seeding.