Why is my late-planted 110 day RM maturing in 100 days (or less) this year?

Recent observations from around the state have found corn maturing at a fast pace this year, especially corn that was planted late.  The most commonly used method for assigning corn hybrid maturity ratings is based on Days to Maturity.  This typically indicates the number of days it would take a corn hybrid to reach physiological maturity or “black layer”.  But temperature drives corn development, not calendar days.  So the “thermal time” to maturity calculated using growing degree days (GDD) is a more accurate measure.  Especially when the growing season has been particularly warmer or cooler than normal.

The chart below shows the difference in cumulative GDD between 2016 and the 30 year mean temperatures beginning on JUNE 1.




We are 6, 7, and 10% above the “normal” GDD accumulation for August 31 at Suffolk, Richmond, and Orange, respectively.

This might explain why a 110 day RM corn is maturing more quickly than expected based on the “day” count.  The plant has actually accumulated heat units at a faster rate this year.

If May 1 is the starting point, we are 3, 4, and 7% above the “normal” GDD accumulation for these sites.  So this effect is likely to seem greater in later planted corn.