Barley (Hordeum vulgare L.) competition: Effects on rapeseed/canola (Brassica campestris L. and Brassica napus L.) growth and yield

Barley frequently becomes a problem weed in central Alberta when rapeseed/canola follows a barley grain crop in rotation. Experiments on crop genotype and density, weed density, relative time of weed emergence and time of weed removal were used to examine the rapeseed/canola (crop) - barley (weed) interaction.;No optimum seeding density for canola (B. campestris cv Tobin, B. napus cv Westar) grown under weedy conditions was identified. Canola branching and pod numbers were reduced when barley was present, which resulted in lower seed yields.;Canola seed yield declined as barley density increased. At barley densities below 50 plants/m;Barley emerging at different times relative to the crop reduced canola seed yield differentially. Yield loss ranged from 7 to 16 g/m;Brassica cultivars/lines with high weed-free seed yields usually maintained higher seed yields when barley was present. Under weedy conditions, the Brassica groups ranked by yield, as a percent of the weed-free value, were: Brassica juncea ;Canola seed yield reduction was proportional to the time barley remained in the crop. Mean reduction in seed yield was 1.3 g/m...