• Korean Journal of Weed Science
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• v.18 no.2
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• pp.146-153
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• 1998

This experiment was conducted to clarify the characteristics of germination and emergence of Panicum dichotomiflorum which is a noxious weed species in direct-seeded rice field. P. dichotomiflorum was planted with several treatments such as different depths of irrigation to verifiy the ecological habits of seedling emergence and growth. In order to know the germination characteristics, Panicum dichotomiflorum seeds, pretreated with low-temperature($4^{\circ}C$) stratification for breaking the dormancy, were germinated under different temperature regimes and water potentials. Germination rates of P. dichotomiflorum was increased from 0% of dormant seed to 1%, 35% and 44% by stratification for 21, 28 and 42 days, respectively. Two dominant weed species in directseeded rice fields, Echinochloa crus-galli and Panicum dichotomitlorum, showed different germination habit under different temperature regimes. Echinochloa crus-galli showed more higher germination rate than Panicum dichotomiflorum at relatively low temperature regime(20/$10^{\circ}C$). Both species germinated faster at 30/$20^{\circ}C$ than at 20/$10^{\circ}C$. When the water potential was lowered, germination of Panicum dichotomiflorum was reduced more drastically than Echinochloa crus-galli. The critical water potential for germination of P. dichotomiflorum was -0.7MPa but Echinochloa crus-galli was affected slightly by the same water potential. The results showed that Echinochloa crus-galli can germinate under more wide range of soil water potential than Panicum dichotomiflorum. Emergence of P. dichotomiflorum was highly affected by irrigation depth and the level of water table. When the depth of irrigation water was increased, emergence of P. dichotomiflorum was dragged and emergence rate showed significant difference under the irrigation depth deeper than 6cm. The maximum depth of irrigation water for survival of Panicum dichotomiflorum seedling was 9cm.

• Korean Journal of Weed Science
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• v.2 no.1
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• pp.7-12
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• 1982

The experiment was studied to know the competitive ability of rice against weeds as affected by rice maturity and plant spacing. For both cultivars, Tongil (12 days later) and Yeongnamjosaeng, the least amount of weed was obtained from the 10 ${\times}$ 10cm plant spacing while no difference between 40 ${\times}$ (10 ${\times}$ 10cm) and 30 ${\times}$ 15cm plant spacings was observed. When weed was nor pulled out by hand, significant yield loss was resulted in 30 ${\times}$ 15cm and 40 ${\times}$ (10 ${\times}$ 10cm) plant spacings while no difference between weeding regime was observed at the 10 ${\times}$ 10cm plant spacing in both cultivars. Rice grain yield was unaffected by plant spacing for hand weeded plot in both rice cultivars. For noweeding plot, however, the highest grain yield was obtained from 10 ${\times}$10cm plant spacing and also this yield was not significantly different from the yield of hand weeded plot while significant yield loss was recognized at the 30 ${\times}$ 15cm and 40 ${\times}$ (10 ${\times}$ 10cm) plant spacings in noweeding plot. There was also a good relationship between weed weight and grain yield for both cultivars (Tongil; Y = 5.68 - 0.0127 X, r = -0.814$^*$; Yeongnamjosaengv Y = 5.04 - 0.0314 X, r =-0.9704$^{**}$). Based on these relationship, weed weight of 188.2g/sq.m for Yeongnamjosaeng and 223.6g/sq.m for Tongil was needed to reduce rice yield by 50%, respectively. This result implied that Tongil compete more efficiently against weed than Yeongnamjosaeng and hence, could be concluded that late maturing cultivar was more competitive against weed compared to early maturing cultivar.

• Weed & Turfgrass Science
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• v.2 no.2
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• pp.159-163
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• 2013

The purpose of this study is to observe the growth habit and investigate a possibility of cultivating the GM rice (CaMsrB2-8) as a rice cultivar having drought resistance. Germination viability test showed that there was no significant difference between the drought-resistant GM(CaMsrB2-8) and non-GM (Ilmi) rice which was the parent variety at the GM rice. All the seeds of CaMsrB2-8 and Ilmi germinated after 6 days. Viviparous germination was not found in CaMsrB2-8 and Ilmi that was grown in greenhouse at $23{\pm}2^{\circ}C$ with water spraying for 40 days. Ratooning of CaMsrB2-8 and Ilmi was observed in 7-14 days and found uniform in field condition. CaMsrB2-8 seemed to grow faster than Ilmi. But CaMsrB2-8 and Ilmi were similar in 14-21 days. Both CaMsrB2-8 and Ilmi showed low seed shattering and more than 90% grains were ripened. All the seeds scattered in the paddy soil surface were not germinated after passing the winter. This study suggests that the drought-resistant GM rice was not significantly different with the parent variety of Ilmi in many agronomic characteristics such as wildness traits.

• Korean Journal of Weed Science
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• v.17 no.3
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• pp.269-280
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• 1997

Collated data from the 1995-1996 field surveys of weed seeds buried in the plough layer of peat soil in Selangor district were analysed to assess species-dominance and spatial pattern of distribution of weed seeds based on selected quantitative indices and index of dispersion. Forty five species within 14 families were recorded of which 24 were broadleaves, 12 grasses and 9 sedges. They comprised ca. 53.2, 31.2 and 15.6%, respectively based on total population counts. Total seed population was ca. $8.14{\times}10^7$ seeds/ha within the fast 25cm soil depth. Wide variabilities in population counts were registered among species ranging from < $7.0{\times}10^4$ seeds/ha for Amaranthus gracilis to ca. $5.64{\times}10^6$ seeds/ha for Heteropogon contortus. Seeds of Cleome rutidesperma was the most abundant(ca. $2.347{\times}10^7$ seeds/ha). Difference in seed population counts may be attributed to inherent variation in fecundity, population fluxes, their spatial distribution patterns and the agronomic practices prevailing in the areas of survey. The profile distribution of soil seed banks was skewed within the first 0 - 10cm depth, comprising ca. 69% of the total seed counts. Seed counts in the 10 - 15, 15 - 20 and 20 - 25cm soil profiles were in the order of 17.9, 8.6 and 4.0% of the total populations, respectively. Weed seeds of all species displayed different degree of aggregated pattern of distribution with variance-to-mean ratios of > 1 and Lloyd's mean crowding($m^*$) values from 1.244 for Cyperus iria, Phyllanthus debilis, Phyllanthus urinaria, Scirpus grosses and urinaria lagopodiodes to 9607.7 for Cleome rutidosperma. Lloyd's patch indices(Ip) ranging from 5.1 for Aeschynomene indica to 188.5 for Bracharia reptans were registered. Differences in the VMR, $m^*$ and Ip values among species suggested inter-alia inherent variabilities in their disposal capacity from seed source and different agronomic practices prevailing in the areas surveyed.

• Weed & Turfgrass Science
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• v.7 no.3
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• pp.209-218
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• 2018

This study was carried out to investigate the occurrence and distribution of ALS inhibiting herbicide-resistant weeds and to estimate the appeared areas of resistant weeds in the paddy fields of Gyeongnam province of Korea in 2017 and 2018 using a soil assay method. Compared with the 2012 survey, this study showed that the infested ratio of ALS inhibiting herbicide-resistant weeds increased from 1.0% to 66.8% and the infested area increased from 876 ha to 49,008 ha. The infested area of ALS inhibiting herbicide-resistant weeds was estimated in Ulsan-si (8.4%), Hapcheon-gun (8.3%), Haman-gun (7.9%), Goseong-gun (7.9%), Hadong-gun (7.3%), Jinju-si (7.2%), Changnyeong-gun (7.0%), Gimhae-si (6.4%), Miryang-si (5.5%), Busan-si (4.9%), Uiryeong-gun (4.6%), Namhae-gun (4.3%), Geochang-gun (4.2%), Changwon-si (3.8%), Geoje-si (2.9%), Yangsan-si (1.8%), Sancheong-gun (0.9%) and Tongyeong-si (0.4%), and the herbicide resistant weeds was not occurred in Hamyang-gun. The most dominant ALS inhibiting herbicide-resistant weeds in paddy fields were Monochoria vaginalis, followed by Echinochloa oryzicola, Lindernia dubia, Scirpus juncoides, Ludwigia prostrata, Cyperus difformis, Sagittaria trifolia and Rotala indica. ALS inhibiting herbicide-resistant M. vaginalis, L. dubia, and E. oryzoides occurred throughout Gyeongnam province, and ALS inhibiting herbicide-resistant S. trifolia and R. indica were only found in Gimhae-si. Therefore, these results will be utilized to estimate population dynamics of ALS inhibiting herbicide-resistant weeds and provide proper management practices in the paddy fields of Gyeongnam province.

• Korean Journal of Weed Science
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• v.5 no.1
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• pp.73-84
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• 1985

25 tank-mixed combinations between Haloxyfop-methyl at 0, 0.05, 0.1, 0.15 and 0.2 kg ae/ha and Acifluorfen at 0, 0.082, 0.163, 0.245 and 0.326 kg ai/ha were applicated at post-emergence on the late-season cropped soybean(Glycine max) fields predominated by grasses and assessed on the weeding efficacy. A most abundant weed species on the experimented fields were found at September (25 species). The broadleaved weed species and sedges were successively and proportionately emerged by the control rate of grass species. From the mono-treatment of each herbicide, Haloxyfop-methyl was recognized as a highly selective one between grasses and soybean, and Acifluorfen between broadleaf weeds and soybean, respectively. By combined application with both herbicides a synergistic weeding efficacy was detected on total weed species, however antagonistic or additive on each weed groups. Among other traits of soybean, stem dry weight was influenced by weed competitions during October, number of pods per plant during August and seed yields during whole periods. For most effective and reasonable weeding, no less than 0.4 kg ai/ha of each herbicides should be applicated in combinations.

• Korean Journal of Weed Science
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• v.17 no.2
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• pp.214-219
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• 1997

The influence of manure, chemical fertilizers, heavy metals and cleaner on the rate of degradation of alachlor in soil was studied. The degradation rate of alachlor in the soil followed first-order reaction kinetics. The half-life was 6.4 days. The degradation was accelerated by the amendment of manure. Adding chemical fertilizers to the soil enhanced alachlor degradation more in the presence of nitrogen than potassium. On the other hand, adding heavy metals or cleaner to the soil decreased the degradation rate. The half-life of alachlor in soil treated with Cd, Cr, Ni, Zn and Cu was 11.0, 8.3, 7.9, 7.2 and 6.7 days, respectively, and that of the cleaner is 7.5 days. The microbial biomass and the respiration rate in the soil were promoted by the amendment of manure and chemical fertilizers, and inhibited by the addition of heavy metals and cleaner. The degradation rate correlate positively with the microbial biomass and the respiration rate.

• Korean Journal of Weed Science
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• v.6 no.1
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• pp.7-12
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• 1986

This experiment was conducted to investigate effects of different water depths on emergence, emerged soil depth and growth of E. crus-galli in Seoul, Korea. Plant number of emergence was decreased with deepened water depth, and dry weight of plant was especially negatively affected. However, a few E. crus-galli were emerged under 24 cm water depth. Soil depth of germination was increased as water depth decreased, and a few E. crus-galli were emerged below 10 cm soil depth under - 12 ㎝ water depth. But most E. crus-galli were emerged in ca. 2 cm soil depth under water depth over 0 cm.

• Korean Journal of Weed Science
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• v.1 no.1
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• pp.52-56
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• 1981

A 2-year field experiment was conducted to determine the influence of early and late soybean (Clycine max Merr) seeding times on competitive relationships between soybeans and annual weeds. Soybeans were planted on May 20 and June 20. Durations of weed competition and weed control were 0, 3, 6, 9, and 12 weeks after planting sad for full growing season. Dominant weeds were Portulaca oleracia, Centipeda minima, Rorippa cantonienais, Chenopodium album, Acalypha australis, Echinochloa crusgalli, and Digitaria sanguinalis. The dry weight of weeds increased with extended competition, especially at early seeding time of soybeans. Soybean yields were decreased as duration of weed competition was extended. More severe yield reduction occurred at late-planted soybeans with early stage weed competition but at early-planted soybeans when weeds competed with soybeans for a 2 weeds and full growing season. The dry weight of weeds emerged after weeding was decreased at early and late seeding times of soybeans as duration of weed control was prolonged. Soybean yields decreased with shortening duration of weed control end this trend of yield reduction was slightly more remarkable at late-planted soybeans than at early-planted soybeans. Late-planted soybeans were required longer than 6 weeks of weed control period to achieve maximum yield as compared to early-planted soybeans.

• Korean Journal of Weed Science
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• v.4 no.2
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• pp.135-142
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• 1984

To obtain the basic information for weed management in polder land, a colligated assessment on weed distribution and it`s plant sociological indices on Gyewha polder land were arranged. At the situation of assessment, the Gyewha polder land was reclaimed with aim with paddy-rice production. As a result of reclamation, the salinity of most soil samples were below 0.3%, and acidity ranged from pH 5.5 to 6.5. Total weed species were counted as much as 17 species (3 gramineae, 7 cyperucese, and 8 broad-leaved species), and a most dominant species, Scirpus maritimus, were succeeded with Monochoria v., Eleocharis a., and Cyperus d., etc. by reclamation. Declining of soil salinity and soil pH, the number of weed species, individuals, biomass, species diversity, evenness, sociability index were increased, but the population particularity was weaken in tendencies. By developing of reclamation, the weed species which is summer annual broad leaf, wind and water disseminating, and tussock formed species are increased instead of salt-resistant, perennial cyperus, and rhizomatous extending species.