• Korean Journal of Weed Science
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• v.15 no.3
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• pp.188-196
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• 1995

Blackgrass and water foxtail are troublesome weeds in a cultivation area of cereals. To know whether water foxtail could substitute for blackgrass as a plant material of screening for the discovery and development of new cereal herbicides, they were compared in a greenhouse and a growth chamber with respect to initial growth characteristics and responses to various herbicides. Blackgrass had a higher germination rate at lower temperature and a higher growth rate at higher temperature as compared to water foxtail. In addition, blackgrass was less sensitive to long day than water foxtail. These results suggest that blackgrass grows better in a cultivation area in spring than water foxtail. As compared to water foxtail, blackgrass showed shightly susceptible responses to herbicides when they were applied to soil surface at one day after seeding. However, the responses to the herbicides of blackgrass and water foxtail were similar with a foliar application of the herbicides at 3 or 4 leaf stage of the plant. Since there were no considerable differences in the herbicidal responses of the two plant species, water foxtail could substitute for blackgrass as a plant material for a primary herbicide screening. When water foxtail was used in a post-emergence screening test, seeding amount of 0.1g/$350cm^2$ and postemergence application of herbicides at 3 to 5 leaf stage were found to be appropriate on the view of alleviating screening efforts in a greenhouse.

• Weed & Turfgrass Science
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• v.4 no.2
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• pp.118-123
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• 2015

Metagenomics is a powerful tool to isolate novel biocatalyst and biomolecules directly from the environmental DNA libraries. Since the metagenomics approach bypasses cultivation of microorganisms, un-cultured microorganisms that are majority of exists can be the richest reservoir for natural products discovery. To discover novel herbicidal substances from soil metagenome, we established three easy, simple and effective high throughput screening methods such as cucumber cotyledon leaf disc assay, microalgae assay and seed germination assay. Employing the methods, we isolated two active single clones (9-G1 and 9-G12) expressing herbicidal activity which whitened leaf discs, inhibited growth of microalgae and inhibited root growth of germinated Arabidopsis seeds. Spraying butanol fraction of the isolated active clones' culture broth led to growth retardation or desiccation of Digitalia sanguinalis (L) Scop. in vivo. These results represent that the screening methods established in this study are useful to screen herbicidal substances from metagenome libraries. Further identifying molecular structure of the herbicidal active substances and analyzing gene clusters encoding synthesis systems for the active substances are in progress.

• 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.

• Journal of The Korean Society of Grassland and Forage Science
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• v.35 no.1
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• pp.17-25
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• 2015

The following experiments were used to evaluate the effect of seeding method and pre-emergence herbicides on weed control and the production of the $sorghum{\times}sudangrass$ [sorghum bicolor (L.) Moench] hybrid under field and in vitro conditions. Under the in vitro condition, we evaluated how different kinds of herbicides affect the rate of seed germination and the growth of early seedlings in the $sorghum{\times}sudangrass$ hybrid treated with herbicides. Simazine, alachlor, and methabenzthiazuron were used, and their concentration levels were 0%, 40%, 70%, and 100%. The germination ratio of the seeds was reduced by the application of simazine, methabenzthiazuron, and alachlor compared with the control (distilled water). The alachlor application severely decreased the sorghum germination ratio. However, seed germination was not greatly influenced by the concentration level of the herbicides. Root and shoot length were increased in the following order: control > simazine > methabenzthiazuron > alachlor. Overall, alachlor significantly reduced root length more than shoot length. The differential tolerance of the $sorghum{\times}sudangrass$ hybrid to pre-emergence herbicides by seeding method was then tested under the field condition. The plants were severely injured by the alachlor application, leading to a great reduction in the number of stems. However, for the simazine and methabenzthiazuron applications the number of stems lost was slightly lower than it was for the alachlor and simazine + alachlor applications. In the seeding method, drilling was more effective in reducing herbicide injury than broadcasting. All of the herbicides effectively controlled weeds. The simazine and methabenzthiazuron applications showed a significantly higher dry matter (DM) yield. However, the alachlor and simazine + alachlor applications severely reduced the DM yield. This result suggests that the alachlor application has a significant effect on plant production. Similarly, the total digestible nutrient (TDN) yield was greatly reduced by the alachlor and simazine + alachlor applications. From the results presented above, we concluded that the yield of DM was the highest for broadcasting with no herbicide. and drilling was the most-effective way to reduce herbicide injury. The simazine application was the most-effective herbicide, showing the highest forage yield and TDN yield.

• The Korean Journal of Pesticide Science
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• v.4 no.3
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• pp.68-74
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• 2000

Penicillium oxalicum (PENOX) has shown the potential as a biocontrol agent(5CA) for control of a weed, clover(Trifolium repens L.) in grass plots. The bioherbicidal activity may be due to germinative and growth capacities and substrate availability of the agent over a range of environmental factors. The influences of different water activities($0.94{\sim}0.995\;a_w$) and temperatures($18{\sim}30^{\circ}C$) on mycelial growth, conidial germination, sporulation oil 2% MEA(malt extract agar) adjusted to different water activities with glycerol, and carbon source utilization using BIOLOG GN MicroPlate were determined in vitro. Decreases in $a_w$ on MEA caused a reduction in mycelial growth and conidial germination depending on temperature. The mycelial growth of PENOX was greatest at $30^{\circ}C/0.995\;a_w$. At some lowered water activity($0.97\;a_w$), the growth was similar between 25 and $30^{\circ}C$, and considerably decreased at lowered temperature($20^{\circ}C$). The germination rate was also greatest at $30^{\circ}C/0.995\;a_w$. Lag phase times for PENOX at $18^{\circ}C$ on MEA were >6hrs at tile whole $a_w$ level tested, and at 18 and $25^{\circ}C$ they were >18hrs and >12hrs at $0.94\;a_w$, respectively. However, its sporulation was some better at $0.97\;a_w$ than $0.995\;a_w$ or $0.94\;a_w$, and better at $20^{\circ}C$ than $30^{\circ}C$. In contrast, the number of carbon sources(niche size) utilized by PENOX varied with $a_w$ and temperature. Under some water stress condition($0.95\;a_w$), the agent utilized smaller number of carbon sources than $0.995\;a_w$ depending on temperature. The niche size at 0.995 and $0.95\;a_w$ were highest at $25^{\circ}C$, and showed 86 and 65, respectively. At $30^{\circ}C$, the niche size at 0.995 and $0.95\;a_w$ showed 84 and 50, respectively. There was no carbon source utilized by PENOX at $0.90\;a_w$ regardless of temperature. These information of tile fungal ecophysiology will be useful for the effective development of BCA.

• Korean Journal of Soil Science and Fertilizer
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• v.25 no.3
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• pp.263-269
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• 1992

These studies was conducted to investigate the influence of ALLELOPATHIC effects of upland weeds on crops and soil microorganisms. The aqueous extract of weed residues were used to identify physiological controll of plant and microorganisms. The results obtained are as follows : 1. The aqueous extract of weeds controlled germination and growth of plant, especially the 5%-extract of Potulaca oleracea suppressed the growth of soybean about 8~12%. 2. The 5%-extract of Potulaca oleracea inhibited effect of phytosynthesis of soybean about 60%. 3. The move the concetration of phenolic compounds in soil, the less a number of actinomycetes and bacteria. 4. The number of soil microorganism(fusarium oxysporum spp.) were decresed as to the concentration of vanillic acid was increased.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.977-986
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• 1996

The uncertainty of rains at the onset of wet season (WS) and the drought risk involved hinder growing more than one rainfed lwoland rice crop per year. Establishing transplanted rice well into the WS leaves insufficient moisture in the soil for subsequent crop. Rice establishment early in the season gives the farmer better opportunities to grow a crop after rice. An experiment was conducted startign in 1993 to evaluate dry seeding of rice through slit soil seeding. It is done utilizing the vertical metering slit seeder for conserving soil moisture coming from the first rains in the early WS to sustain germination and establishment of the seeding at least until the succeeding rains under therainfed lowland (RL) environment. The treatment consisted of slit-seeding the PSBRc 14 into the tilled and nontilled plots at 100kg/ha and at depths of <10 mm (shallow seeding) and 60-70m (deep seeding). The control treatment was broadcast seeded on tilled soil and harrow to cover the seeds The superior crop establishment observed in 1995 WS experiment on nontilled, slit-seeded plots confirmed the results observed in 1993 WS and 1994 WS experiments. Emergence in deep seeding was not significantly different from shallow seeding in nontilled plots giving an average yield of 2.1 t/ha in all slit-seeded plots. This offers an advantage of reduced energy in put in nontilled shallow seeding. However, heavy weed infestation has to be addressed at the early stage of rice in nontilled soil to get the full advantage from slit seeding. The consistently better crop establishment observed in slit seeding over that of broadcast seeding in the WS of 1993, 1994 and 1995 also demonstrates that the slit seeding technology can be adopted with confidence in the rainfed lowland field condition to reduce the risks involved in broadcast seeding.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.21 no.2
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• pp.258-268
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• 1976

This study was conducted in order to know the ecology and to establish the control method of Potamogeton distinctus A. BENN. The tubers of Bog pond weed was almostly located at soil depth of 10 cm to 20cm, germination rates and number of formed tubers were different according to transplanting depth of soil. Effects of herbicides application on weeds were different according to leaf-stage of pondweed, and the pondweed were withered to death by absorption of Avirosan into the leaves. It was suitable to keep water depth at 3cm level until about a week after Avirosan application.

• Korean Journal of Environmental Agriculture
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• v.15 no.1
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• pp.46-69
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• 1996

The studies were conducted to obtain the basic information of the effects of pollutants on plant species and to select the plant species showing specific responses to the pollutants. For these purposes, paraquat, ammonium, and cadmium as a source of oxidative stress, nitrogen toxicity, and heavy metal toxicity respectively were treated to the plant species. Among the tested plants, Lamiaceae, Brassicaceae, and Caryophyllaceae were tolerant to paraquat, whereas Poaceae and Asteraceae were sensitive. Especially Mosla dianthera of Lamiaceae, Hemistepta lyrata and Aster pilosus of Asteraceae, and Paspalum thunbergii of Poaceae showed higher tolerance than others. Paraquat resistance was related with life style, overwintering capacity, so perennial and biennial species showed higher tolerance than annual species. In response to ammonium, Poaceae showed higher resistance while Fabaceae and Caryophyllaceae showed sensitiveness. Weed species having tolerance to ammonium were Echinochloa crus-galli var. praticola, Panicum dichotomiflorum, Setaria glauca, Chenopodium album, and Solanum nigrum, while Mosla dianthera, Arenaria serpyllifolia and Perilla frutescens var. japonica showed sensitiveness. In the response of plant species to cadmium, Digitaria sanguinalis, Amaranthus lividus showed higher resistance, whereas Galinsoga parviflora, Plantago asiatica, Ambrosia trifida, and Paspalum thunbergii showed sensitiveness. The injured degree on germination stage by pollutants did not related with injured degree on matured stage. During germination, the root elongation was more sensitive than shoot elongation by pollutants, paraquat, ammonium, and cadmium.

• Korean Journal of Weed Science
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• v.12 no.3
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• pp.200-222
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• 1992

The results of recent researches for improvement of seedling stand in direct seeded rice on the dry paddy in Korea were summarized as the following ; a variety to be cultivated should be chosen the characteristics of high percentage germination under low temperature, shorter period of shoot emergence, and better growth of the mesocotyl and shoots. Meanwhile, there was 40% increase in seedling stand at the treatment of removal of the seed awn under using the drill seeder. After seeding the rice seed covered with soil of 3cm depth was better seedling emergence and also there was the hightest seedling emergence at the 70% of moisture content of the soil. In addition, the application of the Release containing GA 10% enabled to increase the seedling stand and furthermore it was effective under deep seeding depth. The optimum seeding date should be seeded around May 10 when mean air temperature is above 12-13$^{\circ}C$ so that may establish more less 70% in seedling stand. Based on an appropriate seedling stand of 150/$m^2$, the optimum seeding rate was 5kg/10a. It was the best in seeding method using drill seeder and the most desirable recommended seeding method was the drill seeder in terms of seedling stand. In order to improve seedling stand water management was more effective in canal irrigation and in drainage at 6hr after irrigation following by the seeding process. On the other hand, for the increase of seedling stand under flooded condition a variety might have characters being better germination at low concentration of dissolved oxygen and vertically deeper growing of the crown root. Also, seedling stand was able to increase with the seed coating of $CaO_2$in the flooded soil. It was possible to be seeded on the early part of May being mean air temperature of avove 10$^{\circ}C$ and the optimum seeding rate was 5kg/10a. For an effective water management water would be flooded up to 3cm depth for 2-3 weeks after seeding. The rice plant grown under the direct seeded cultivation might be not so much strong in lodging resistance compared to that grown under the transplanting and moreover direct seeded rice cultivation under flooded condition would be more weak growth of the rice plant than that on dry paddy. Meanwhile, the lodging would be affected by the seeding rate, the soil depth after seeding. and seeding method even in the same variety. In particular, roots in the lodging pattern of direct seeded rice cultivation under flooded condition were largely distributed on the soil surface so that resulted easily in the lodging. In general, the lodging resistance would be greater as seeding rate and amount of N fertilizer application are lower and soil depth after seeding is higher. Among the introduction of different seeding method the high ridged drill seeding method on dry paddy soil resulted in the lowest in the lodging index and also it was lower in the drill seeding method than in the scattering seeding method under flooded condition. In case of more than 150 seedlings per $m^2$ there was a severe lodging due to high lodging index at the 3rd and 4th internodes. The effective lodging prevention was able to at the treatment of the Inabenfide at 45 days before heading and the Uniconazol at 15 days before heading which caused the shortage by 10-15cm in culm length. Also, fertilizer management using split application of nitrogen would be contributed the reduction of lodging at the rate of 20-30-20-20-10%(basal-5th leaf stage-7th leaf stage-panicle initiation stage-heading stage) on the dry paddy soil.