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What corn test weight really means

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Corn test weight is often misunderstood. A common misconception is that higher test weight corn yields more. And lower-yielding fields have a lower test weight. To understand corn test weight, think of corn yield in terms of pounds harvested per acre rather than bushels per acre. The concept is confusing because we refer to a bushel in terms of the volumetric measurement, but weight is what determines payment. Here are a few facts to help you think in terms of pounds:

  • The standard weight of a bushel of No. 1 yellow corn is 56 pounds.

  • Test weight will vary based on several factors, primarily moisture content. Think of test weight as another quality check, like foreign matter, damage, etc.

  • If test weight drops to 54 pounds or below, a price discount may be applied at market, which is why staying above the threshold is important.

  • Test weight can exceed the 56-pound threshold, but no premiums are given for high test weight corn.  

The importance of test weight
As an example, let’s say we harvest two different hybrids from the same test plot. Hybrid A yields 12,000 pounds per acre with test weight of 56 pounds. Hybrid B yields 10,000 pounds per acre with test weight of 60 pounds. Hybrid A is the clear winner because it produced more pounds of grain per acre while maintaining the 56-pound test weight threshold. Hybrid B yields 2,000 pounds less per acre but isn’t rewarded for exceeding the 56-pound threshold. Dipping below the threshold, however, say 54 pounds or below, would likely trigger a price dock at the elevator.

Factors that can impact test weight
Lower test weights at harvest could stem from several factors the crop experienced during the growing season, including:

  • Stress during grain fill resulting from drought

  • Varying degrees of ear and kernel rot

  • Additionally, late planting due to wet spring conditions means farmers could be dealing with high moisture grain. High moisture grain tends to be swollen and sticky, which impedes grain flow and pack into a volumetric bushel resulting in lower test weight. As grain dries and shrinks, test weight improves.

Here are a few more common causes of lower test weight.

Test weight management
Managing test weight can be tricky as it is a factor highly dependent on environmental conditions throughout the lengthy grain fill period. There are a few management factors that can help.

  • Select hybrids with consistent and adequate test weight from year to year, coupled with a good disease package and below-ground insect protection for at-risk acres.

  • Maintain an optimum fertilizer application plan, especially nitrogen, to ensure nutrients are available at the end of the season.

  • Reduce planting populations if you feel your soils are unable to support higher densities.

For more information about test weight, visit with your retail agronomist.

What corn test weight really means

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