Investigation development and distribution status of weeds in tobacco fields of Guangdong province

The weeds in 5 soil types of tobacco fields in the main tobacco plantation regions of Guangdong province,were surveyed by measurements and visually scoring the level of weeds and their infestation to tobacco.105 species of 82 genera belongina to 29 families were recorded.There were 15 main species according to the importance of weeds,including Digitaria sanguinalis,Ecrusgalli,Acalypha australis,Polygonum caespitosum,Setaria viridis,etc.The results showed that the main weed communities and dirtribution were different between the following 5 soiltypes in Guangdong province: in purple territories,there were 4 main species including Polygonum caespitosum,Acalypha australis,Ecrusgalli and Eclipta prostratas in purple territories dryland,there were 5 main species including Acalypha australis,Setaria viridis,Cyperus rutundus,Xanthium sibiricum and Digitaria sanguinalis;in limestone dryland,there were 4 main species including Digitaria sanguinalis,Ecrusqalli,Arthraxon hispidus and Ageratum conyzoides;in the limestone sand mud tian,there were 4 main species including Echinochloa crusgalli,Eleusine iudica,Arthraxon hispidus and Cyperus difformis,in the tian Ma mud,there were 4 main species including Digitaria sanguinalis,Cardamine flexuosa,Arenaria serpyllifolia,Polygonum caespitosum and Chenopodium serotinum.