By Chad Lee, Extension Agronomist
Farmers are considering replanting some corn fields. If replanting occurs, there are questions about maturity groups and when to expect harvest.
Later Plantings Reach Blacklayer Faster
As corn planting is delayed, heat units or growing degree days (GDD's) accumulate more rapidly. This more rapid accumulation of GDD's essentially speeds up the growth and development of hybrids. For example, a hybrid that requires 2700 GGD's to reach blacklayer needs about 130 days when planted on April 1 in Mayfield, KY. That same hybrid planted May 15 requires about 109 days, a 21-day difference.
Hybrids that require 2700 GDD's are often listed at about 114-day relative maturity. Planting date can greatly effect the actual number of days required to reach blacklayer.
Use Earlier Maturities with Later Plantings
For far western Kentucky, even late-planted corn is at minimal risk for fall freeze damage. For the remainder of Kentucky, farmers will want to plant hybrids that are about 114-days or less for late plantings. For example, planting a 118-day corn on June 1 in Mayfield should reach blacklayer by October 7, or 14 days before the expected first freeze. But, the same hybrid planted June 1 in Henderson will reach blacklayer about November 15, or 10 days after the expected first freeze.
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