Dockage

Dockage consists of the material that arrives with a grain delivery but is not the grain being sold: chaff and straw fragments left by threshing, weed seeds picked up in the field, soil and dust, and other fine matter light or small enough to separate from sound kernels by mechanical cleaning. It is defined functionally rather than by a fixed list of substances — the operative test is whether the prescribed device removes it, not what it is made of.

Because the test is procedural, dockage is only meaningful in reference to the specific cleaning device and settings the applicable standard prescribes. A general-purpose grain cleaner run at different settings, or a different make of dockage tester, will not reproduce the same figure. This is why grade standards specify the apparatus in detail rather than leaving the determination to inspector judgement.

A representative sample is drawn from the lot and passed through the cleaning device specified by the applicable grade standard. What the device removes is weighed and expressed as a share of the sample, and that share is applied to the whole delivered lot. The figure is then reported alongside — but separately from — the numerical grade.

Dockage and foreign material are frequently confused because both describe non-grain content, but they are assessed at different stages and have different consequences. Dockage is removed first, by the prescribed cleaning device, and is deducted from weight. Foreign material is what remains mixed with the grain after that dockage removal — finer or more tightly associated matter that the cleaning step does not take out — and it is treated as a grade factor rather than a weight deduction.

A lot can therefore be low in dockage but high in foreign material, or the reverse, and the two figures should never be read as interchangeable or averaged together. Buyers and sellers relying on a contract that specifies one when the other is meant risk a genuine commercial dispute.

Removing dockage cleans a lot of bulk trash — chaff, straw, weed seed, dust — but this is a physical separation, not a decontamination step. Cleaning does not remove mycotoxins that have already formed within the grain itself, and the material screened out is often where contamination concentrates: weed seeds, mould-affected fines, and insect-damaged fragments tend to be exactly the kind of light, small material a cleaner separates out. Treating a cleaned lot as a safe lot conflates a commercial weight adjustment with a food- or feed-safety determination, which it is not.

• Dockage material is not necessarily worthless: screenings can have recognised feed value where permitted.
• Because screenings concentrate weed seed, mould, and toxin from the original lot, their feed use is regulated rather than unrestricted.
• Confirming safety requires appropriate testing, not an inference from the fact that a lot has been cleaned.