Volunteer canola is a common weed in canola growing areas. Volunteer canola originates from high harvest losses and a persistent seedbank that through developing seed dormancy can persist for several years in rotation. Few herbicides are available to manage weeds effectively in soybean production and volunteer canola, due to a lack of effective herbicide options, is a major weed in this important pulse crop. Field studies have been conducted at various sites in Manitoba to quantify soybean yield loss caused by volunteer canola at various densities in both narrow- and wide-row soybean. The same level of soybean yield loss was observed at more than twice the volunteer canola density in narrow-row soybean (2.8 plants/m2) than in wide-row production systems (1.2 plants/m2). Another study evaluated a combination of mechanical and cultural practices to reduce the volunteer canola seedbank in the crop before soybean to reduce volunteer canola populations in subsequent soybean crops. Although results of this trial are still ebing analyzed, preliminary results indicate that level of residual soil nitrogen may affect the competitive balance between soybean and volunteer canola, although this appears to be specific to canola variety. Preliminary results from the an additional tank-mix partner trial suggest that faster acting in-crop herbicides (some members from groups 6 and 14) tended to cause to lower volunteer canola and higher soybean biomass accumulation at flowering.
