In order to investigate effect of different periodical weed interference
on yield and yield component in winter canola (Brassica napus var.
Okapy) a field study was conducted in Tarbiat Modarres University on 2004.
A randomized complete block design with 3 replication was used to study
two sets of treatments. In first set of treatments, the crop was kept
weed-free until 2, 4, 6 and 8 leaves, initiation of flowering, 50% pod
set and harvest stages. In second set of treatments weeds were allowed
to grow with crop until above stages. Results showed that periodical weed
interference had no influence on seed thousand weight and seed number
on pods on lateral branches but caused to significantly reduction on pod
number on main and lateral branches and seed number on pod on main shoot
with increasing weed interference duration. Seed yield significantly affected
and decreased by weed interference duration exceeding.