Effect of weed competition on morphophysiologic indices, yield and yield components of rapeseed (Brassica napus L.) cv. Zarfam in Varamin

In order to investigate the effect of weed competition on morphophysiologic indices, yield and yield components of rapeseed, a research project was conducted using a randomized complete block design with three replications at Natural Resources and Agricultural Research Center of Tehran Province in Varamin, during 2008-2009 growing season. Treatments included periods of weed competition or noncompetition with rapeseed based on growth different stages of crop. Treatments were applied in two groups: I. Weed interference until 2, 4, 6, 8 leaf stages, emergence of flowering bud initiation and harvest stages and II. Weed free treatments until the above mentioned growth stages. The continuity of weed competition to thelater stages of crop growth caused that the final height of rapeseed increased by plants which in turn increased the node intervals on the main stem. The results also showed that weed removal time had significant effects on number of secondary branches per plant, height of the lowest pod bearing branch, pod number per plant, seed number per pod, 1000 grain weight, biological and grain yield, harvest index and oil yield, but there were no significant differences between treatments on pod length and percent of oil production. Overall, it is found weed control in this period can prevent yield reduction significantly.