Study On Weed Community Of Rice Fields In Liaoning Province

According to the present situation of weeds infestation in rice fields in Liaoning province, a comprehensive and systematic investigation was carried out in 2003-2004.It is the first time in the past twenty years to study on the situation of weed damage and community composition more spcifically than ever.It mainly studied weed category quantities, community composition and succession in ecology aspect not in pattern of weed category surey. Based on the methods of fixed-point arithmetic and five rating damage level of weed by visualization, date analyses of weed Abundance,Frequency, Uniformity and Density were made by SPSS.Furthermore , the difference of weed damage markable levels were compared through variance analysis. On the basis of comprehensive analysis in weed community and cause of formation, suggestions were put forward, which were weed control in light of different weed communities. The specific investigation results are as follows:The present situation of weed infestation and damage: The result showed that there are 39 weed species which belong to 16 families. The main harmful weeds in paddy field are Spirogyra communis (hass.) kUtz, Lemna minor L., Echinochloa crucially (L.) Beau., Sagittaria itrifolia L., Murdannia keisak (Hassk.) hand. Mazz., Monochoria korsakowii Regel ET Maack , Echinochloa crusgalli (L.) Beauv.var.mitis (Pursh) Peterm ,Bidens tripartitea. L., Echinochloa oryzicola (Vasing.) Vasing., Scirpus planiculmis Fr.Schmidt, Sagittaria Pygmaea Miq., and Monochoria vaginalis (Burm.f.) Presl ex Kunth.The relative abundances of all these weeds are 39. 04%, 31. 31%, 29.63%, 25.19%, 23.42%, 22.24%, 21.42%, 20.66%, 20.43%, and 17. 28%.Weed community and cause of formation: On the basis of investigation date, the level of dominant weeds is analyzed. The dominant weed categories in each rice growing region are affirmed. In Dandong region, there are 10 dominant weed species, which are Echinochloa caudate Roshev. Monochoria korsakowii Regel et Maack, Murdannia keisak (Hassk.) hand. Mazz, Sagittaria itrifolia L., Bidens tripartitea L., Echinochloa crusgalli (L.) Beauv.var.mitis (Pursh) Peterm., Monochoria vaginalis (Burm.f.) Presl ex Kunth, Monochoria vaginalis (Burm.f.) Presl ex Kunth, Scirpus planiculmis Fr.Schmidt, and Lemna minor L.; In Panjin and Yinkou region, there are 11 dominant weed species, which are Monochoria vaginalis (Burm.f.) Presl ex Kunth, Echinochloa crucially (L.) Beau., Lemna minor L., Scirpus planiculmis Fr.Schmidt, Sagittaria itrifolia L., Monochoria korsakowii Regel et Maack, Echinochloa crusgalli (L.) Beauv.var.mitis (Pursh) Peterm., Sagittaria Pygmaea Miq., Bidens tripartitea L., Phragmites communis Trin., and Monochoria vaginalis (Burm.f.) Presl ex Kuntharev; In Anshan and Liaoyang region, there are 10 dominant weed species, which are Monochoria vaginalis (Burm.f.) Presl ex Kunth, Lemna minor L., Echinochloa crucially (L.) Beau., Echinochloa oryzicola (Vasing.) vasing., Sagittaria itrifolia L., Bidens tripartitea L., Echinochloa crusgalli (L.) Beauv.var.mitis (Pursh) Peterm., Monochoria korsakowii Regel et Maack, Scirpu bernaemontani Gmel.,and Sagittaria Pygmaea Miq.; In Shenyang region, there are 11 dominant weed species, which are Lemna minor L., Monochoria vaginalis (Burm.f.) Presl ex Kunth, Echinochloa crucially (L.) Beau., Bidens tripartitea L., Echinochloa oryzicola (Vasing.) vasing., Murdannia keisak (Hassk.) hand. Mazz, Sagittaria itrifolia L., SagittariaPygmaea Miq., Echinochloa crusgalli (L.) Beauv.var.mitis (Pursh) Peterm., Monochoria vaginalis (Burm.f.) Presl ex Kunth, and Monochoria korsakowii Regel et Maack; In Tiding region, there are 10 dominant weed species, which are Monochoria vaginalis (Burm.f.) Presl ex Kunth, Lemna minor L., Sagittaria itrifolia L., Echinochloa crucially (L.) Monochoria korsakowii Regel et Maack. Echinochloa oryzicola (Vasing.) vasing. Scirpus planiculmis Fr.Schmidt, Bidens tripartite^. L., and Monochoria vaginalis (Burm.f.) Presl ex Kunth.. All these dominant weeds with rice compose the rice-weed community in different rice growing regions. Environment factor, cropping system and herbicide using played important role in the process of weed community in different regions in Liaoning province.Weed community succession and cause of formation: Compared to the date of 1990 s investigation in Shenyang region, Analyses about weed community succession of rice fields in Shenyang region are taken. The result showed that a change of weed community structure in quality and quantity has been taken. Inl990's investigation; some weed species with rice formed the rice-weed community, which included Echinochloa crucially (L.) Beau., Scirpus planiculmis Fr.Schmidt, Eleocharis yokoscensis (Franch.et Sav.)Tang et Wang, Sagittaria itrifolia L., Alisma orientale(sam.) Juzepcz,Patamogeton distinctus A.Benn., Scirpus triqueter L., Cyperus difformis L., Bidens tripartite^. L., Juncellus serotinus (Rottb.) C.B.Clarke, Scirpus juncoides Roxb. In the past ten years, the weed community of rice field in Shenyang region has turned into "Broadleaf weed+ Grassy weed + Sedge weed" pattern from "Grassy weed + Sedge weed + Broadleaf weed" pattern. From all the dominate weeds, the proportion of vicious weeds are rising. The dominant and...