| critical period of weed control in winter canola (brassica napus l.) in a semi-arid region. | in order to determine the critical period of weed control in winter canola (brassica napus l. cv. okapi) an experiment was carried out at research field of tarbiat modarres university, tehran, iran on 2004-2005 growing season. fourteen experimental treatments which divided into two sets were arranged in randomized complete blocks design with four replications. in the first set, the crop was kept weed-free from emergence time to two-leaf stage (v2), four-leaf stage (v4), six-leaf stage (v6), eigh ... | 2008 | 18819576 |