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Not All Hybrids Have Similar Test Weight, Grain Quality

Not All Hybrids Have Similar Test Weight, Grain Quality
Differences show up quickly in a large test plot comparing hybrids.

If you have 40 hybrids in a test plot, how many will test out at weights above 56 pounds per bushel, and how many below 56 pounds per bushel? The 56 pounds per bushel mark is the standard accepted weight for corn.

That's a loaded question. It all depends upon the hybrids that are in the plot. Dave Nanda says that is because test weight is highly controlled by genetics. Some hybrids have higher test weights than others, even when exposed to the same weather conditions. Nanda is the director of Genetics and Technology for Seed Consultants, Inc.

Test weight varies: It's a safe bet that if you weigh 30 hybrids in the same day from a plot, test weights will vary in a wide range.

What you do know is that all the test weights won't be the same. Besides varying by genetics, it's likely in a group of that many hybrids, maturity varies at least some, so moisture content will vary. Corn at higher moisture tends to have lower test weight, Nanda says. Once it's dried the test weight goes up because the water is removed. Water weighs less than starch.

What really counts when doing a test plot is the number displayed on the side of the screen as the scale read-out, Nanda says. It's important to know moisture content and test weight, but yield is the ultimate measuring stick. Of course that's yield corrected back to dry bushels.

Just because a hybrid has a high test weight does not mean it will be the highest yielder, Nanda says. Sometimes it is, and sometimes it isn't the highest yielder. It's an independent trait. Both are roughly tied to genetics.

When running a large test plot recently, one seed rep reported that both moisture contents and test weights were all over the board. When he pulled a sample from the weigh wagon to measure moisture and test weight, he could also get a visual feel for overall grain quality. There were also differences in grain quality, he noted.

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