عنوان مقاله [English]
In order to evaluate the effect of tumble pigweed competition on yield, yield components and grain quality of six cultivars of sunflower, a factorial experiment based on completely randomized design was conducted at the research farm of College of Agriculture, University of Birjand in 2012. The factors were four different weed densities (0, 5, 10 and 15 plants/m2).and six cultivars of sunflower (Azargol, Jame Esfahan, Syrna, Farrukh, Progress and Euroflor). The results showed that increasing of weed density decreased yield and yield components of sunflower. When weed density increased from zero to 15 p/m2, grain yield of sunflower decreased by 40/2 %. Jame Esfahan cultivar produced the most grain yield (5.789 kg/ha) among other cultivars, and Farrukhi cultivar had the least percentage of grain yield loss in Weed density of 15 p/m2. In generally, Progress, Euroflour and jeme-esfahan cultivars have the most competitiveness and Azargol cultivar showed the least competitiveness against tumble pigweed.