Wheat - Chapter 4 | Official Grain Grading Guide

Determination of dockage


Dockage is assessed to the nearest 0.1%.

Dockage is defined under the Canada Grain Act as “any material intermixed with a parcel of grain, other than kernels of grain of a standard of quality fixed by or under this Act for a grade of that grain, that must and can be separated from the parcel of grain before that grade can be assigned to the grain.” Dockage is removed by following the cleaning procedures described in this chapter.

The sample as it arrives is referred to as the uncleaned or dirty sample. Its weight is the gross weight of the sample. Dockage is assessed on the gross weight of the sample.

Dockage is assessed in two stages.

  1. Follow Normal cleaning procedures, using the Carter dockage tester.
  2. Follow procedures for Cleaning for grade improvement. This cleaning can be done at any time after the cleaning assessment has been completed.

Dockage not reported


Dockage is not reported for samples grading

  • Wheat, Sample CW/CE/CAN Account Fireburnt
  • Wheat, Sample Salvage
  • Wheat, Sample Condemned

For Wheat, Sample CW/CE/CAN Account Admixture, dockage is not reported for removable material similar in nature to the admixture.

Normal cleaning procedures


Wear gloves and a mask to handle any samples that you suspect may contain hazardous substances.

1. Set up the Carter dockage tester with the following specifications

Feed control #6
Air control Minimum #4 (increase according to the nature of the material)
Riddle No. 25
Top sieve No. 6 buckwheat
Centre sieve No. 5 buckwheat
Bottom sieve No. 5 buckwheat
Sieve cleaner Off

2. Using a Boerner-type divider, divide the uncleaned sample to obtain a representative portion.

  • Official samples shall be at least 1 kg.
  • Unofficial samples shall be at least 1 kg.

3. Turn on the Carter dockage tester.

4. Pour the sample into the hopper.

5. After the sample has passed through the machine, turn on the sieve cleaner control for 2 to 3 seconds to remove kernels lodged in the sieve.

6. Turn off the dockage tester.

7. Lightly snap the retainer rod of the aspiration pan to loosen material gathered on the air screen.

8. Remove the aspiration pan.

9. Handpick whole sound threshed kernels of wheat from the portion passing over the riddle and return them to the cleaned sample.

Composition of dockage

Dockage includes:

  • Wheat with long rootlets, unthreshed wheat heads, and material other than wheat removed by the No. 25 riddle
  • Material removed by No. 5 buckwheat sive in the lower position
  • Material removed by aspiration
  • A maximum of 10% of soft earth pellets handpicked from the clean sample
  • Material removed by Cleaning for grade improvement

Cleaning for grade improvement

If the grade of a sample can be improved by additional cleaning, perform the cleaning and add the additional material to dockage. Cleaning for grade improvement can be done at any time after the cleaning assessment has been completed.

The purpose of this cleaning is not to remove all foreign material, but rather to reduce the admixture of conspicuous separable material to within the grade tolerance.

  1. After the cleaning assessment has been completed, examine the material to be removed and select your equipment according to that material. See the table, Cleaning for grade improvement, for the list of equipment.
  2. Pass the sample through the Carter dockage tester, or sieve the sample by hand, depending on the material.
  3. Weigh the additional dockage and add it to the original dockage


When you use a hand sieve, move the sieve from left to right 30 times, using a sifting motion. One time is one complete motion from the centre, to one side, to the other side, and back to the centre. The total distance from left to right is 20 cm, or about eight inches.

Cleaning for grade improvement - Wheat

Cleaning for grade improvement for wheat
Material to be removed Equipment Composition of dockage
Broken kernels No. 6 buckwheat hand sieve
No. 10x10 wire hand sieve

If the weight of brokenkernels in the cleaned sample is over the grade tolerance, you can remove up to 5.0% of the gross weight in broken kernels to improve the grade.

For example, if a sample of CWRS contains 12% broken kernels by gross weight, you can remove enough broken kernels to bring the percentage to 7%, which brings the sample within the grade tolerance for No. 3 CWRS. Add the maximum 5% broken kernels to dockage.

See Shrunken and broken.

Bunt balls Carter dockage tester, using the setup for Normal cleaning procedures, but with air control at a maximum setting of 7

If there is no odour, remove bunt balls and add to dockage.

If there is an odour, bunt is a grading factor.

See Common bunt.

All foreign material (other than stones and wild oats) No. 6 buckwheat hand sieve
No. 10x10 wire hand sieve
Add material to dockage, if the grade is improved as a result.
Stones No. 6 buckwheat hand sieve If the weight of stones and other material removed is
  • 5.0% or less of the gross weight, assess as dockage.
  • More than 5.0% of the gross weight, see Stones in Grading factors, or the relevant grade determinants table.
Wild oats Carter dockage tester, using the setup for Normal cleaning procedures, but with No. 1 riddle
No. 10x10 wire hand sieve
Everything removed is dockage.

Optional analysis

Where a shipper requests special cleaning of a carlot of grain at a terminal elevator, and the elevator manager agrees, dockage material will be analyzed for the presence of grain. The percentage and grade of any grain contained in the dockage will be reported.


  1. Analyze the official sample.
  2. Record the following on inspection records:
    • The percentage by gross weight to the nearest 0.1% and the grade of wheat.
    • The percentage by gross weight to the nearest 0.1% and the grade of grain separable from dockage.
    • The percentage of dockage.

95.0% Wheat, No. 1 CWRS

4.0% Domestic Mustard Seed, No. 1 CAN Oriental

1.0% dockage