Relative Competitive Ability of Canola Cultivars Versus Small-Grain Cereals.

Canola production in Canada is dominated by herbicide-resistant, hybrid cultivars.  These cultivars have greater competitive ability than previously popular open pollinated cultivars resulting in improved canola competition with weeds and less reliance on herbicides.  However, no published research has compared the competitive ability of the new herbicide-resistant, hybrid cultivars with various small-grain cereal cultivars.  Direct-seeded (no-till) experiments were conducted at five western Canada locations (Beaverlodge AB, Lacombe AB, Lethbridge AB, Saskatoon SK, and Scott SK) from 2006 to 2008 comparing the relative competitive ability of several open pollinated- and hybrid-spring canola cultivars with spring barley, rye, triticale, and wheat.  Cultivated oat was seeded across plot areas and oat biomass was used to determine the relative competitive ability of each crop cultivar.  After a single pre-seeding glyphosate burn-off application, no further herbicides were applied to the plots.  Generally, barley produced the greatest crop biomass and was the most competitive species; this was particularly the case when monocot weed biomass was considered.  Hybrid canola produces less biomass than most cereal cultivars, but often competed well against oat.  At high temperature sites [greater accumulated growing degree days (GDD) - 0 C base], most cereals were more competitive than canola.  However, at low temperature sites (low GDD accumulations), canola was as competitive as some cereals.  Under conditions favourable to canola, several canola cultivars were more competitive with dicot weed species than any small-grain cereal.  Opportunities for integrated weed management practices that rely on less frequent herbicide applications in canola are most likely in relatively low temperature environments.