• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.1
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• pp.32-37
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• 1999

The experiment was conducted to investigate emergence response of lowland weeds at different soil moisture contents, burying depths and upon changes in soil moisture. Rice germination was over 50% at all burying depths under aerobic condition, but the emergence rate of the soil surface placed seeds in saturated and flooded conditions decreased by 19% and 29%, respectively, as compared with that of aerobic condition. Rice seeds at burying depth of over 3 cm did not emerge at all. The emergence rate of Echinochloa crus­galli (L.) Beauv. in aerobic condition was lower than 30%, but the emergence pattern of E. crus galli (L.) Beauv. at different soil moisture contents and seeding depths was similar to that of rice. Emergence behavior of lschaemum rugosum Salisb., Ludwigia octovalvis (Jacq.) Raven and Sphenoclea zeylanica Gaertn. which are dominant lowland weed species in the Philippines also differed depending on soil moisture conditions and burying depths. lschaemum rugosum Salisb. emerged at all burying depths under aerobic condition, whereasLudwigia octovalvis (Jacq.) Raven emerged only at 0 cm deep under saturated and aerobic condition and Sphenoclea zeylanica Gaertn. at 0 cm deep under flooding condition. Weed seeds planted at 1, 3, and 5 cm deep in continuous flooded and saturated condition did not emerge at all, but upon a change of soil moisture condition from saturated to drainage (S$\rightarrow$D) and flooded to drainage (F$\rightarrow$D), grass weeds began to germinate again and the average emergence rate in S$\rightarrow$D and F$\rightarrow$D were 26% and 5% forE. crus­galIi (L.) Beauv., 9% and 8% forI. rugosum SaIisb., respectively. Weed seeds buried in soil in the pot showed great emergence at S$\rightarrow$D but did not emerge under continuous flooded condition. The diversity index accounting for dominance degree and occurrence aspect of weed, was the lowest at F$\rightarrow$D.

• Korean Journal of Weed Science
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• v.8 no.3
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• pp.265-272
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• 1988

This experiment was carried to investigate the germination pattern in relation to temperatures and lights, and the emergence pattern in relation to seeding depths, lights and the alpha amylase activity of Youngia sonchifolia, Lactuca indica var. laciniata, Ixeris dentata var. albiflora and Ixeris polycephala. In Y. sonchifolia, the optimum germination temperature was $25^{\circ}C$, the optimum seeding depth to emerge was 0 mm and it could emerge in 0-5mm. In L. indica var. laciniata under cool storage, the optimum germination temperatures were $19^{\circ}C-28^{\circ}C$, the optimum seeding depth was 5mm and it could emerge in 0-20mm. In L. indica var. laciniata under room storage, the optimum germination temperature was $25^{\circ}C$ the optimum seeding depth was 5mm and it could emerge in 0-10mm. In I. dentata emerge was and 0mm and it could emerge in 0-5mm. In I. polycephla, the optimum temperatures were $16^{\circ}C-19^{\circ}C$, the optimum seeding depth to emerge was 0mm and it could emerge in 0-5mm. The alpha amylase activity was lower Y. sonchifolia, L. indica var. laciniata and I. dentata var. abiflora than barley cultivar Dongbor#1. And the increased pattern of alpha amylase activity was likely to it of germination rate.

• Korean Journal of Weed Science
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• v.15 no.4
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• pp.313-320
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• 1995

The major weeds observed in soybean(Glycine max(L.) Merr.) culture at the paddy field where transplanted rice was cultivated in previous year were Digitaria spp., Echinochloa spp., Chenopodium ficifolium, Rorippa islandica and Stellaria alsine. C. ficifolium and R. islandica increased as soybean was cultivated for two years in the same field. Weed biomass decreased by 84.8% as the seeding date was delayed from April 26 to May 20. Most of weeds started to emerge from 20 days after seeding(DAS) until 40 DAS, and higher seed yield was obtained by eliminating the weeds emerged until 40 DAS. The development of soybean branches, pods stem diameter was severely injured by weed interference, and thus soybean seed yield was reduced by 70% in comparison with a full season weed free plot. Herbicides such as pendimethalin, metolachlor, metolachlor+prometryn and alachlor controlled very effectively weeds present in soybean culture in rice-soybean rotated paddy field.

• Korean Journal of Weed Science
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• v.11 no.3
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• pp.224-228
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• 1991

This study was carried to know factors affecting emergence of major upland weeds in soil in order to get basic information on weed control methods. Firthy eight percent of weed seeds were distributed within soil surface to 10cm in soil and 2% of weed seeds were observed in 40~50cm soil layer in field. As planting depth was deeper, emergence of weeds became poor. However Capsella bursa-pastoris can emerge at soil surface. Amaranthus retroflexus, Amaranthus lividus, Porturaca oleracea, Chenopodium album, Solanum nigrum upto 3cm, Eleusine indica, Echinochloa crus-galli, Setaria viridis, Digitaria sanguinalis upto 7cm. Emergence of weeds was very poor in very acid soil but good in soil pH 5.5~6.0. However emergence of weed was not affected by pH 3.5~4.0 or above. Emergence of E. indica, C. bursa-pastoris, A. retroflexus, A. lividus, C. album, E. crus-galli, Solanum nigrum, and S. viridis was good in loam soil and P. oleranea, D. sanguinalis in sandy loam soil. Emergence of weed seeds was not affected by fertilization.

• Korean Journal of Weed Science
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• v.18 no.1
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• pp.1-11
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• 1998

This experiment was conducted to investigate weed infestation and to determine effective weed control methods in direct-seeded rice. Twenty two weed species occurred in dry- and water-seeded rice, which was mainly composed of annual weeds. Dominant weed species in dry-seeded rice were Cyperus difformis, Echinochloa crus-galli, Aneilema keisak and Digitaria sanguinalis in discending order. Dominant weed species in water-seeded lice were E. crus-galli, C. difformis, Monochoria vaginalis and Scirpus juncoides. E. crus-galli emerged at 7 days after sowing. In water-seeded rice, E. crus-galli emerged at 5 days after sowing, and M vaginalis, S. juncoides and C. difformis at 8~10 days after sowing. Mean days to emerge important weeds was 20 days in dry-seeded rice and 13 days in water-seeded rice. Leaf development of weeds was faster than that of rice in dry-seeded rice. In water-seeded rice, E eras-galli was more vigorous than rice, but leaf development of other weeds were slower than that of rice. Changes in number of weeds and dry weight oil weed species varied depending upon weed species in the direct-seeded rice. Dry weight of weeds were increased greatly from 30 days to 60 days after sowing in dry-seeded rice. Number of weeds tended to increase up to 40 days after sowing drastically, and then trend of the increase was dull thereafter. Dry weight and number of weeds increased up to 20~60 days after sowing in water-seeded rice. Most effective herbicide treatments was foliar application of cyhalofop/bentazon at 20 days after sowing followed by fenoxaprop/bentazon at 45 days after sowing in dry-seeded rice. All herbicide treatments except foliar applications were very effective to control weeds in water-seeded rice. Slight phytotoxicity was observed in foliar applied fenoxaprop/bentazon at 45 days after sowing in water-seeded rice, but it did not affect rice yield.

• Korean Journal of Weed Science
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• v.14 no.3
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• pp.163-170
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• 1994

The experiment was conducted in 1993 to find out a simple prediction method of weeds and to make the prediction models of weeds in paddy fields. The annuals producing fine seeds were apt to emerge at sampling soil only, on the contrary the perennials and the annuals producing large seeds tended not to emerge at sampling soil due to the miss of seeds at sampling. There was no appropriate regression between a total number of weeds emerged at sampling soil and that of weeds occurred in fields. The important annual weeds occurring in fields were able to predict by the number of weeds emerged at sampling soil, but it was difficult to predict the important perennial weeds. In case of Bidens tripartita producing large seeds and Eleocharis kuroguwai producing large tubers, the prediction coefficients were high as above 1.0, and that of Echinochloa crus-galli and Sagittaria pygmaea were comparatively high as 0.175 and 0.172, respectively. However the coefficients of the other weeds were much low as below 0.08. The prediction models for 9 species were made. The model of six species including E. crus-galli, M. vaginalis, R. indica, B. tripartita, E. triandra and S. pygmaea were linear regression with high significance, however that of 3 species including C. difformis, S. juncoides and E. kuroguwai were curve regression with high significance.

• Korean Journal of Weed Science
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• v.8 no.2
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• pp.158-163
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• 1988

Several factors affecting emergence and tuber formation of lowland perennial weeds were studied at the Yeongnam Crop Experiment Station in 1988. Period of tuber germination start to final tuber varied by species. Eleocharis kuroguwai and Sagittaria trifolia required longer than 10 days at $30^{\circ}C$ for this while Cyperus serotinus and S. pygmaea needed about 4 days. Application of gibberellic acid shortened this period while Uniconazole application delayed. E. kuroguwai and C. serotinus had ability to emerge under 20cm depth placement. However, S. trifolia could not emerge under 15cm depth. All species decreased their growth with increase in planting depth. E. kuroguwai had least correlated between dry matter production and tuber formation. Clipping of above ground part negatively related with tuber formation eventhough the effect of clipping time was differed by species. The most critical clipping time was 60 days after eremergence (DAE) for E. kuroguwai and 90 DAE for C. serotinus. Covering of colored polyethylene film was also related with tuber formation with varing effects. In general, the order of effectiveness for tuber formation were black. orange. blue and red. Application of Uniconazole and Pachlobutrazol effectively controlled the formation of tuber of E. kuroguwai and this effect enhanced by early application.

• Korean Journal of Weed Science
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• v.10 no.4
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• pp.269-276
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• 1990

Weed species belonging to the broadleaf family prevailed in the experimental sites followed by Cyperucea and grass family. In terms of life cycle, the dominant weed species were the perennial weeds rather than annual weeds. Most of weeds were emerged between 30-60days after transplanting in Chuncheon and between 40-60 days after transplanting in Hongcheon and Hoengseong areas. Among agronomic characteristics of rice affected by weed emergence were decrease of plant height by 2-4㎝, panicle number by 1.3-2.9, spkelet by 3. 7-7.5, ripening rates by 3.3-6.5%, and milled yield by 12-17%.

• Korean Journal of Weed Science
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• v.4 no.2
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• pp.125-129
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• 1984

Emergence and early growth of Eleocharis kuroguwai, Potamogeton distinctus, and Sagittaria pygmaea were examined at 10, 14, 18, 22, 26, and $30^{\circ}C$ of soil temperatures using soil temperature gradient bath. Eleocharis kuroguwai emerged at $14^{\circ}C$ or higher temperature and % emergence was increased as soil temperature increased up to $26^{\circ}C$ but decreased at $30^{\circ}C$. Percentage of emergence in Potamogeton distinctus was very low at $10^{\circ}C$ but most of them were emerged at $14^{\circ}C$ or above. Emergence rate was faster as soil temperature increased. Percentage of emergence in Sagittaria pygmaea was increased until 10 days after planting as soil temperature increased but final percentage of emergence was 100% at all temperature. Number of days required for 80% emergence was shortened as soil temperature increased and Eleocharis kuroguwai and Potamogenton distinctus required longer duration to emerge compared to Sagittaria pygmaea. Eleocharis kuroguwai and Potamogeton distinctus required higher accumulated soil temperature for emergence compared to Sagittaria pygmaea. Optimum soil temperature for early growth after emergence of Eleocharis kuroguwai, Potamogeton distinctus, and Sagittaria pygmaea were 26, 18-22, and 18-$26^{\circ}C$, respectively.

• Korean Journal of Weed Science
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• v.12 no.1
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• pp.8-15
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• 1992

Arrowhead (Sagittaria trifolia L.), a perennial weed dominant in paddy field, is considerably difficult to control by herbicides. The investigation on the effects of environmental factors on emergence of arrowhead tuber can aid for controlling this weed. The results exmined were as follows : From the results of emergence characteristics at different levels of temperature, arrowhead tuber could germinated at 15$^{\circ}C$-40$^{\circ}C$. The optimal temperature for basal emergence was ranged from 25 to 30$^{\circ}C$. Basal emergence at 15$^{\circ}C$ and 20$^{\circ}C$ began at 56 and 12 days after tuber plantation, respectively and were later than those at the optimal temperature. At the different levels of shading, all the tested tubers could emerged. The days required for basal emergence at 25% and 50% shading plots were shorter than those at 70%, 80% and non-shading plots. The basal emergence was more effective under blue and clear films than any other phyto-selective materials. Some of arrowhead tubers could not emerged under green, red and yellow films. On the soil pH, the basal emergence was best at soil pH 6.0 and 7.0. At soil pH 4.0, 5.0 and 8.0, the required days for emergence were longer than those at soil pH 6.0 and 7.0 and some of tubers could not emerged. Arrowhead tubers more then 0.5 g showed the shorter shooting days than those less than 0.5 g. Tubers were able to emerge at water depth ranging from 0 to 20 cm. At 3 cm and 5 cm water depth, the required days for basal shooting were shorter than those at any other levels of water depth. The emergence of basals was best at molding depth of 0 cm, and the rates at 3 to 5 cm of plantation depth were decreased. At 10 cm plantation depth, the shooting rate was significantly decreased.