Corn Yield Races to Fill Before First Frost

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The majority of Iowa's corn crop is in the dough stage. Statewide it's still behind on the dent stage, but that hasn't stopped many field scouts predicting high corn yields across Iowa.

Iowa State University Field Agronomist Mark Johnson who scouts fields of 10 central Iowa counties says, "We had a lot of people out there right after pollination, doing yield estimates and coming up with incredible numbers. I was hearing over 300. A lot of 285's."

Johnson says there's a lot more to determining yield than counting kernels.

"The thing you got to keep in mind is: the number of kernels is part of the the picture, but the depth in that kernel is very important, too. And how much we fill that, contributes a lot to the yield."

The fill is found by cutting a cob in half and checking the kernels.

"So, what a lot of people do is they follow the milk line down, to see the progression." He says, "That'll just keep coming down as it gets closer to the end and that is physiological maturity. And then immediately after that, there's an abscission layer. Where a layer of cells dies and compresses and it becomes black."

Johnson says with all the recent cool days, Iowa is behind on heat units. He says the state is anywhere from five days to 15 days behind schedule, "And so then the concern is, can this milk line get all the way down and can we hit physiological maturity before frost?"