Evaluating the average seedbank addition of canola in producers’ fields
Seed 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.
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