عنوان مقاله [English]
In order to study interferential effect of lambsquarters (Chenopodiun album) on some of physiological traits and yield of marigold (Calendula officinalis), a factorial experiment was conducted in Islamic Azad University, Tabriz, Iran, based on randomized complete block design in three replications during 2014. Studied factors were weed densities (0, 2, 4, 6 and 8 plants per meter row) and its relative emergence times (along with crop, 10, 20 and 30 days after crop). Results indicated that in plots with 6-8 weed plants per meter row time to 12th leaf appearance in marigold delayed 5.3 days. In plots with only 2 weed plants, crop LAI value was similar to the control. Weed emergence time was more effective than its density on biomass. Crop biomass reduced 6.3 and 1.5 g m-2 per one weed plant increasing in meter row and one day earlier weed emergence, respectively. Weed competition had more negative effect on crop flower yield than its biomass. Lambsquarters could decrease crop yield when it was emerged with more than 4 plants per meter row. With considering of 5% permissible yield loss of marigold in competition with lambsquarters, its economic loss threshold determined when at least 2 weed plants per meter rowemerged 10 days after marigold and compete along with crop until late growth season. It was recommended to controlling of lambsquarters while at least to weed plants per meter row of marigold emerged before 10th day of emergence.