عنوان مقاله [English]
نویسندگان [English]چکیده [English]
For evaluation of weed competition and different nitrogen levels interaction on some growth traits of sunflower a split plot experiment based on randomized complete block design was conducted with 24 treatments and 3 replications in research farm of college of agriculture of Birjand University in 2010. The main factor was 3 levels of nitrogen (0, 100 and 200 Kg ha-1) and the sub factor was different weed competition periods containing of 3 levels of weed free, 3 levels of weed infested until phonological stages of two leaf (V2), four leaf) V4) and head visible stage of sunflower (VR) with 2 control (all season weed free and weed infested) treatments. The results showed that the power of competition of weeds with sunflower increased with the application of nitrogen fertilizer up to the level of 100 Kg ha-1 of nitrogen fertilizer consumption, but increases of nitrogen more than this level can be favor for sunflower. The main weeds were barnyard grass, bindweed, common mallow, red root pigweed, common lamb squarters and hoary cress. Increasing the period of weed competition, increased their dry weight but reduced their density. Nitrogen could also significantly increase biological yield, height, head diameter, head dry weight and seed yield of the sunflower, but the intensity of this increase was influenced by weed competition :Calibri; mso-hansi-font-family:"Times New Roman";mso-ansi-language:EN-US;mso-fareast-language: EN-US;mso-bidi-language:FA'>کاربرد نیتروژن نیز توانست عملکرد بیولوژیک، ارتفاع، قطر طبق، وزن خشک طبق و عملکرد دانه آفتابگردان را به طور معنیداری افزایش دهد، ولی شدت این افزایش تحت تاثیر رقابت علفهای هرز قرار گرفت.