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Crop Watch: Many experts say yes, but proof is elusive.

Tom Bechman, Editor, Indiana Prairie Farm

August 26, 2016

3 Min Read

Is invisible corn loss real or not? Can corn lose yield if left standing in the field in the fall due to changes that occur in the kernels that have nothing to do with stalk lodging or dropped ears? Are you money ahead if you harvest early and dry the corn vs. letting it dry in the field?

You’ve heard about juries that take several days to reach a verdict in criminal cases. You’ve also heard about hung juries, where the only consensus the jury can reach is that it can’t reach a consensus. When that happens, the judge declares a mistrial. The prosecutor decides whether to retry the case or not.


The concept of corn losing yield due to dry matter loss caused by continuing respiration inside kernels just standing in the field was first noted in scientific circles roughly 30 years ago. And the jury is still out, trying to decide if the concept is real! In a criminal case, that would have to be a world record for length of time for a jury to make a decision.

In some people’s minds, it’s a hung jury. The idea makes sense and "appears" to show up sometimes, but not every time. Other people think it’s real and don’t question it. Your view may impact when you decide to harvest corn. If you believe in invisible yield loss, you’ll likely start harvesting earlier at a higher moisture level, pay the drying bill, and believe you are money ahead because you harvested more bushels than if you had let the grain dry in the field.

Tough to pin down

One year ago it appeared there was a perfect opportunity to determine if this phenomenon were true or not in the Crop Watch ’15 field. The cooperators harvested half the field in late September, switched to harvesting soybeans, and finished harvesting the Crop Watch field three weeks later. Were yields, all corrected to 15.5% moisture, lower at the later harvest date?

The answer turned out to be: "well, yes, sort of, maybe, maybe not." Overall yields were lower at the second harvest date, but the farmers felt there were mitigating factors. Soil type changed, and for the most part, corn harvested later was on less-productive soil. There were two hybrids planted side by side, but there wasn’t replicated testing. With at least one hybrid, there was more stalk lodging by the second harvest date, which could have resulted in more harvest loss. In the end, it was — you guessed it — another "hung jury."

He believes

Gary Woodruff is convinced that invisible corn loss is real and should prompt you to harvest as early as is practical. He is the conditioning applications manager for GSI. "Corn becomes mature at a moisture level somewhere between 26% and 35%, but there are biological factors going on inside the kernel between 30% and 15%,” he says.

“The kernel is making normal changes to become a seed ready to sprout, and in that process, it cannibalizes some of the starches, some of the energy, from the kernel. This is often called respiration.”

Woodruff says the process can lower test weight, resulting in lower yield. “When corn drops to 15% moisture, as it does when harvested late, losses of 10% to 15% or more are common," he continues. “So the earlier you can get your crop out, the more yield you are going to have.”

About the Author(s)

Tom Bechman

Editor, Indiana Prairie Farm, Indiana Prairie Farmer

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