Effect of crop protection and herbicides management on weed species distribution in wheat fields

In order to investigating theeffects of crop rotation and applying of herbicides on weed distribution in irrigated wheat fields of Kermanshah province، this study was performed during 2011-2012. Multivariate analysis (RDA) revealed the significant relationship between composition and species frequency and exerted management techniques. The first and second features of RDA indicated 57%، 74. 9% and 58. 3% distribution variance under the effect of crop rotation، grass herbicides and rotation، and broadleaf herbicides and rotation respectively. The highest effect was for the continuously wheat cultivation which had a positive correlation with the frequency of the weeds including Lolium rigidum، Hordeum spontaneum، Avena ludoviciana، Lithospermum arvense and phalaris brachystachys. Application of the herbicide clodinafop propargyl and rotation between wheat-barley and wheat-sugar beet had a low correlation with grass weeds. The weeds including Sinapis arvensis، Carthamus oxycantha، Vicia assyriaca and Galium tricurnutum in the rotation wheat- barely were not controlled by applying 2،4-D، tribenuron methyl and Sulfosulfurun and had a high density.