In order to investigate the effects of row intercropping wheat ( Triticum aestivum L.) with canola ( Brassica napus L.) on weed populations an experiment was conducted at the Agricultural Research Station of Ferdowsi University of Mashhad during fall growing season in 2009. For this purpose a randomized complete block design with three replications and six treatments was used. The treatments included canola and wheat alone, one row of canola + one row of wheat (1:1), two rows of canola+two rows of wheat (2:2), three rows of canola+three rows of wheat (3:3) and four rows of canola+four rows of wheat (4:4). Weed samplings were done in two stages (early and late of growing season). Then, weeds were counted and measured their dry matter. The results revealed that the highest and lowest amounts of relative frequency were obtained for ryegrass ( Lolium rigidum) and wild spinach ( Chenopodium album) with 2.27-6.82% and 36.36-62.79%, respectively. The maximum and minimum values of weeds dry matter were observed in wheat alone and 4:4, respectively. These findings suggest that intercropping increased diversity and it decreased weed number, density and population.
