What if a grower calibrated wrong and seeded at 3 pounds/acre instead of 5 pounds as intended? If that seed had a thousand kernel weight (TKW) of 5 grams, the actual number of surviving plants per square foot could be lower than the minimum 4-5 plants required for canola to reach its yield potential. Click here to see how important it is to recalibrate when switching crops or varieties.
Should the grower reseed?
Not likely. This thin stand is not optimal for yield (see the graph below) but a thin stand at the end of May has better yield and quality potential than the alternative, which is reseeding.
The key is to protect those few plants. Thresholds for everything are lower with a thin stand. Watch closely for insects and consider spraying for flea beetles when damage is only 20%. Keep weed competition to a minimum. And know that the large bushy plants that this crop produces will have wider windows of susceptibility for sclerotinia. If the risk is high, a split application of fungicide may be warranted because the flowering period will be longer.
If growers know immediately that they made a mistake with the seeding rate, they could try to overseed to bump the rate. But if the mistake is not known for a couple days, just leave the crop, assess it as it emerges, and manage accordingly. Don’t try to overseed because it could damage germinated seedlings and create a multi-stage crop that presents management challenges all season long.