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Corn – Chapter 17
Official Grain Grading Guide

Determination of dockage

Definitions

Dockage is only assessed when producers deliver corn to country elevators in eastern Canada. Dockage is assessed to the nearest 0.1%. In all other locations, this material is called Cracked corn and foreign material (CCFM) and is a grading factor.

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 section of the manual.

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 not reported

▲ Important: Dockage is not reported when corn is graded

Corn, Sample CE Account Fireburnt
Corn, Sample Salvage
Corn, Sample Condemned

Normal cleaning procedures: Carter dockage tester

▲ Important: Wear gloves and a mask to handle any sample which you suspect may contain hazardous substances.

Assess dockage before assessing test weight.

1. Set up the Carter dockage tester as follows:

Feed control	# 10
Air control	off
Riddle	none
Top sieve	No. 12 round-hole (moisture 25.0% or less) No. 14 round-hole (moisture over 25.0%)
Centre sieve	blank tray
Bottom sieve	none
Sieve cleaner	off

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

Official samples should be at least 900 g.
Unofficial samples should be at least 750 g.

3. Turn on the Carter dockage tester.

4. Pour the sample into the hopper.

5. After the sample has passed through the machine, turn off the Carter dockage tester.

6. Remove the sample pans containing the corn and broken corn.

7. Determine dockage, using the list under Composition of dockage.

Normal cleaning procedures: manual procedures

Manual procedures for normal cleaning of corn require

No. 12 round-hole sieve for corn with 25% moisture or less
No. 14 round-hole sieve for corn over 25% moisture

Using a Boerner-type divider, divide the uncleaned sample to obtain a representative portion.
- Official samples should be at least 900 g.
- Unofficial samples should be at least 750 g.
Sieve approximately 250 g at a time on the appropriate hand sieve until all possible material has fallen through the sieve.
Handpick material remaining on top of the sieve as described under Composition of dockage.

Composition of dockage

All material which passes through the No. 12 or No. 14 round-hole sieve
All foreign material and pieces of cob handpicked from the sample, excluding stones