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Digging into the details of dockage

Dockage can be an expensive issue on your farm. Learn what it is and how it’s measured

It’s important to use the right sieves when figuring out dockage in wheat or canola.

Your grain is in the bin but your job is far from over. Now it’s time to sell that crop.

But how do you know you’re getting a fair shake at the local elevator? A little knowledge can go a long way, and so we took a look at the dockage procedures for wheat and canola on the Canadian Grain Commission’s website.

Here’s what you need to know about assessing dockage in wheat and canola.

Hand-sieving canola

Canola needs to be hand-sieved before it’s run through the Carter dockage tester. You’ll need a representative one kg sample, taken from the dirty or uncleaned sample with a Boerner-type divider. Divide that sample into 250 gram portions for each sieving.

Choose a round-hole sieve that will remove large material, but let through reasonably sound canola. The slotted sieve should cut the amount of inseparable material so that it’s within the grade tolerance, while minimizing loss of reasonably sound canola.

When it comes to shaking the slotted sieve, there’s a standard protocol, too. You should use a sifting motion, moving it left to right. Each motion should start in the centre, move to one side, then the other, then back to centre. Do that 30 times. Total distance from left to right is about eight inches.

Combine all four cleaned, 250 gram portions before switching on the dockage tester.

Running the Carter dockage tester

Both canola and wheat samples need to go through the Carter dockage tester. But the settings and procedures are different for the two crops (see chart below).

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For canola, pour the entire one kg sample into the dockage tester’s hopper. It should be tested for aspiration only. Then you should pull out at least 10 grams with a Boerner-type divider. Determine the percentage by weight of conspicuous admixtures and soft earth pellets in this small sample.

For wheat, you’ll also need a representative one kg sample, taken from the uncleaned sample with the Boerner-type divider. The entire wheat sample needs to go through the dockage tester. Some kernels may get stuck in the sieve, so run the sieve cleaner for a couple of seconds once the sample has gone through the machine.

Switch off the dockage tester. Loosen material gathered on the air screen by snapping the retainer rod of the aspiration pan. Remove the aspiration pan and handpick any whole, sound, threshed wheat kernels from the area over the riddle. Drop them into the cleaned sample.

What is dockage

So what exactly is dockage? On a practical level, here’s what falls under dockage for wheat:

  • Unthreshed wheat heads and wheat with long rootlets.
  • Non-wheat material removed by the riddle.
  • Material removed by the bottom sieve.
  • Material removed by aspiration.
  • Up to 10 per cent of soft earth pellets handpicked from the clean sample.
  • If cleaning to improve grade, material removed in that process.

And here’s what counts as dockage for canola:

  • During hand-sieving, material caught on top of the round-hole sieve or that passes through the slotted sieve.
  • In the dockage tester, material removed by aspiration or that passes over the No. 000 riddle
  • Hand-picked from the cleaned sample: Conspicuous admixture, within grade tolerances; and Soft earth pellets.
  • Material removed if cleaning to improve the grade.

Commercially clean primary samples may have up to 0.5 per cent for reasonably sound and broken canola deducted from the dockage’s gross weight. But there’s no allowance for primary samples that aren’t commercially clean.

Sample grades don’t include conspicuous admixture as dockage. Instead, if the admixture weight tops two per cent, it becomes a second reason for the sample grade.

Pulling up your grades

If your crop falls short, you can have it cleaned again to bump it to a higher grade. Here’s how to do it:

  1. Once your wheat or canola has been cleaned, figure out what equipment you’ll need to remove the extra material (see chart below).
  2. Depending on the material, the sample will need to be sieved by hand or poured through the Carter dockage tester again.
  3. Weigh the new dockage and add it to the original dockage.
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Cleaning sample grade canola

What happens if you’ve cleaned your canola for grade improvement, but it only qualifies for Sample Canada, Account Admixture? You should figure out the dockage using the No. .035 slotted sieve and a round-hole sieve. The Carter dockage tester’s air control should be set at No. 5.

If the canola falls into the Sample Canada, Account Damaged, use the Carter dockage tester with air control set at No. 5. Also use round-hole and slotted sieves. The slotted sieve should be suited to removing weed seeds and broken grain.

The chief grain inspector needs to approve any variation from these settings.

Optional analysis

If both the elevator manager and shipper agree to a special cleaning of a carlot of grain, the dockage can be analyzed for the presence of grain. This agreement needs to be sent to the Canadian Grain Commission in writing before the dockage is examined. Elevator stocks will be adjusted based on the percentage and grade of any grain found in that dockage.

The procedure is the same for wheat and canola. The official sample is analyzed, and the following information is recorded on inspection records:

  • The grade and the percentage by gross weight to the nearest 0.1 per cent.
  • The grade of grain separable from dockage and the percentage by gross weight to the nearest 0.1 per cent.
  • The percentage of dockage.

For example, with canola, you could end up with the following results:

  • 95 per cent canola, No. 1 CAN
  • Four per cent barley, No. 1 CW
  • One per cent dockage

For more information on grading and dockage, check out the Grain Grading Guide at

About the author

Field Editor

Lisa Guenther

Lisa Guenther is field editor for Grainews based at Livelong, Sask. You can follow her on Twitter @LtoG.



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