Calibrate the drill between seed lots

2010 - Issue 3

Canola thousand seed weight (TSW) can range from less than 3 grams up to 6 grams or more. This can have a dramatic effect on seeding rate.Click here to see a CCC video on the topic. To calculate an appropriate pound per acre seeding rate for each seed lot, use this formula:

Seeding rate (lb./ac.) = [9.6 x desired plant density (plants/ft2) x TSW (grams)] ÷ estimated seed survival (%, expressed as a whole #).

For example, if TSW is 4 grams, desired plant population is 10 plants per square foot and estimated seed survival is 50%, then the formula goes like this: (9.6 x 10 x 4) ÷ 50 = 7.7 pounds per acre.

Once the appropriate seeding rate has been determined, check that seeding equipment is properly calibrated to deliver the desired pounds of seed per acre. Consult the operator’s manual for recommended calibration instructions, or follow the following procedure:
1. Measure out 100 feet.
2. Collect the seed from several drill runs over this
distance. Weigh the collected seed.
3. Calculate the seeding rate using this formula: Grams of seed ÷ number of drill runs collected ÷ row spacing (inches) x 12 = seeding rate (lb./ac.)
For example, if the grower collects 18.75 g from 5 drill runs and row spacing is 9”, then the actual seeding rate is 18.75 ÷ 5 ÷ 9 x 12 = 5.0 lb./ac.

Adjust the seeder and recalibrate until the target seeding rate is achieved. Then record the drill settings, TSW and seeding rate. For more detail, click here to download the factsheet Plant Populations for Profitability and click here for tables that give a seeding rate based on TSW, target plant stand and estimated seed survival.

On that note, with the size of hybrid seed today — 5 to 6 grams per 1,000 seeds is typical — growers are looking at 7 pounds or more per acre to hit the target minimum stand of 7 plants per square foot. That’s based on a survival rate of 50%. Since most growers plant 5 pounds per acre, or less, they need a survival rate of 70% or 80% to hit the target plant stand. That may be possible this year, given the moisture conditions, but only if they do everything else right. See article 1.


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