Volunteer canola (B. napus) in western Canada

Non-Peer ReviewedIn western Canada, survey and small plot research has shown that volunteer canola persists for at least four years in rotation (Derksen at al. 1999; Thomas et al. 1999). It is not clear whether this is due to persistence of the seedbank additions during harvest or the result of replenishment of the seedbank by subsequent volunteers. We are examining the life cycle of volunteer canola beginning with the seedbank additions incurred during harvest and as well as a focus on the seedbank ecology of this species in western Canada. Research in Europe has shown that B. napus can be readily induced into secondary dormancy by a combination of darkness and moisture stress (Pekrun, 1994). Nonetheless, field studies have revealed that only a small proportion of seeds persist via secondary dormancy in Europe (Pekrun et al. 1998). Canadian B. napus genotypes differ in their potential for induction into secondary dormancy using a laboratory assay. While some genotypes consistently exhibit low potential for the induction into secondary dormancy, others consistently exhibit high potential for the induction into secondary dormancy. High temperatures are perhaps the most important contributing factor to the induction of secondary dormancy, while low temperatures rapidly remove secondary dormancy. These observations suggest the seed ecology of a typical summer-annual weed. Furthermore, observations in a field experiment in 2000 revealed that volunteer canola germination was limited to the early portion of the growing season. Spring seedbank evaluations indicated far greater seed viability than was reflected by field emergence. It is was not clear if the seeds that did not emerge lost viability or were induced into secondary dormancy as our lab results would suggest. A more detailed field experiment examining the persistence of B. napus and induction into secondary dormancy was initiated

Evaluating the average seedbank addition of canola in producers’ fields

Non-Peer ReviewedSeed shatter in canola leads to a considerable yield loss and the dispersal of canola seed into the seed bank. The volunteer plants can then create a weed problem in the subsequent crops and result in crop yield loss. In 2010 a study was conducted to measure the harvest losses of canola in producers’ fields. A total of 26 fields were surveyed within 150 km radius from Saskatoon, SK. Out of these fields, 3 swathed and 3 direct combined fields from Kernen Crop Research Farm were included to compare the amount and time of seed loss in both harvesting methods. Sampling was done within 3 weeks of harvesting. Transects were laid at three random locations in each field from the center of one swath to the center of the adjacent swath. Six 0.25 m2 quadrats were kept in each transect at 1m interval. Plant counts were taken in each quadrat before sampling and were included in the total seed loss. Then the remaining crop residue, shattered seeds and some surface soil were removed from each quadrat using Ultra Shop Vacuum Cleaner. The bulked sample of each transect was air dried and cleaning was done using Carter Dockage Tester with different Sieve combinations. Finally the weight of pure seed and thousand seed weight were measured to calculate the amount of seed loss per unit area. The average seed loss was found to be 135.5 kg ha-1, which is equivalent to 5.8 % of the total yield and it resulted in seed bank addition of 4400 seeds m-2. Yield loss among producers ranged from 2.2 to 13.6 % (13 to 70 times the normal seeding rate). An average of 379 seeds m-2 were germinated (ranged from 6 to 2224 seeds m-2) within 3 weeks of harvesting. Direct combining resulted in higher seed loss than swathing. Both natural dehiscence of pods and seed loss from combining contributed for the buildup of canola seed bank