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Northern Illinois Agriculture

University of Illinois Extension
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How far to go to reach maturity in the northern Illinois corn crop?

Recently I've heard several agronomists who have broached the subject of an early (or even normal) frost and what impact that will have on our 2013 corn crop. Today I was asked how many days are yet needed to reach maturity. While some variation can be expected by variety and the weather conditions we experience in the remainder of the growing season, the following can be used as a guide.

We encourage you to scout your own fields, but as a reference corn I scouted today was early R4 (dough) stage.

  • 11 days from R1 (silk) to R2 (blister)
  • 8 days from R2 to R3 (milk)
  • 6 days from R3 to R4 (dough)
  • 7 days from R4 to R5 (dent)
  • 33 days from R5 to R6 (R6= physiological maturity, safe from frost)

Average first frost dates (32 degrees) in northern Illinois counties range from October 4th to October 11th.
Illinois frost information is accessible from the Illinois State Water Survey

Using the October 4th date provides us 48 days. Once you do the math, corn currently at R4 needs approximately 40 days to reach maturity, corn at R3 needs approximately 46.

Lets hope for
  1. warmer weather
  2. a late frost (or at the very least, an average and not early frost)

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