Corn: Determination of dockage


In Eastern Canada the terms of delivery or terms of a contract will determine if dockage is to be assessed. In Western Canada dockage may only be assessed on tough, damp, moist or wet corn. The CGC will only assess dockage upon request. Dockage is assessed and recorded to the nearest 0.1%. Once dockage material has been removed it will not be reintroduced to the sample to determine the grade.

Cracked Corn and Foreign Material (CCFM) is a grading factor and will be assessed when determining the grade.

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 for

  • Corn, Sample CE Account Fireburnt
  • Corn, Sample Salvage
  • Corn, Sample Condemned
  • Unofficial samples declared as processed

Normal cleaning procedures

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

Assess dockage before assessing test weight.

Procedures for normal cleaning of corn require

  • number 12 round-hole hand sieve for corn with 25% moisture or less
  • number 14 round-hole hand sieve for corn over 25% moisture
  1. 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.
  2. Sieve approximately 250 g at a time on the appropriate hand sieve until all possible material has fallen through the sieve.
  3. Handpick material remaining on top of the sieve as described under Composition of dockage.

Composition of dockage

  • All material which passes through the number 12 or number 14 round-hole sieve
  • All foreign material and pieces of cob handpicked from the sample, excluding stones
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