• Korean Journal of Weed Science
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• v.31 no.3
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• pp.221-228
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• 2011

Weed control is of fundamental importance when planting horticultural crops, particularly during the establishment phase. Weeds compete for nutrients, water and light, and can severely threaten the survival and early growth of newly planted crops. Failure to control weeds represents one of the single most important factors leading to crop loss. Knowledge on the existence of the diversity of weed species in greenhouses is of our main concern in this study in order to develop a most efficient and effective weed control strategies. Sixty-two greenhouses were surveyed in 3 cities and counties of Gyeongnam area in March to October 2009 to investigate the feature of weed occurrence in polyvinyl chloride (PVC) after harvesting of the main crops. Forty-one weed species were identified and classified to 18 families which were composed of 14 annual weeds, 18 summer annual weeds and 9 perennial weeds. On the other hand, broadleaf, grasses and sedges recorded with 30, 7 and 4 weed species, respectively. Asteraceae was the most dominant weed species (9 species) noted followed by Poaceae (7 species), Cyperaceae (4 species), Caryophyllaceae and Brassicaceae (3 species respectively) and other families have 1~2 species. The dominant weed species occurred in the greenhouse based on the summed dominance ratio. These weeds were Digitaria sanguinalis, Cyperus iria, Portulaca oleracea, Rorippa islandica, Mazus japonicas, Cardamine flexousa, and Eclipta prostrata and others. Weed occurrence in the greenhouse after horticultural crops consisted of summer annuals (4 species), winter annuals (3 species), and perennial annuals (1 specie). The dominant species occurred in tilled soil based on summed dominance ratio of weeds were Cardamine flexousa (88.1%), Eclipta prostrate (57.4%) and Portulaca oleracea (55.2%). Comparison of weed occurrence was thoroughly surveyed also in which field without PVC, weed species were Portulaca oleracea (55.2), Eclipta prostrata (57.9%) and Trigonotis peduncularis (25.1%) and field with PVC, the identified weeds were Portulaca oleracea (98.75), Trigonotis peduncularis (49.1%), and Eclipta prostrata (36.8%).

• 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.