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The amount of “days65533;? a corn plant needs to grow from emergence to maturity is often referred to as growing degree units (GDU). These units are calculated based on a formula using the high and low temperatures of each day along with upper and lower limit temperature parameters. By using these values, approximate GDU needed to reach specific corn growth stages can be estimated (Table 1). Daily GDU accumulation increases as the growing season progresses.
Previous Ohio and Indiana research results indicate a reduction in GDU requirement was about 6.5 GDU per day when planting was delayed beyond the normal planting window.1 While the actual decrease in GDU varied somewhat among years in the research, it does indicate that late-planted products typically mature in fewer than expected GDUs. This decrease in GDU requirement, however, usually comes at the cost of decreased yield potential compared to timely planting.
Careful consideration of several factors should be given prior to switching to an earlier corn product include:
The remainder of the growing season does make a difference:
Your local agronomist can provide recommendations for corn relative maturity groups and seeding rates that fit specific situations.
Sources: 1 Nafziger. E. 2009. Illinois agronomy handbook. 24th edition. Chapter 2. University of Illinois Extension. http://extension.cropsciences.illinois.edu/handbook/. 2 Myers, B and Wiebold, W.J. 2013. Corn maturity ratings and delayed planting. University of Missouri. http://ipm.missouri.edu/IPCM/2013/5/Corn-Maturity-Ratings-and-Delayed-Planting/. 3 Nielsen, R.L. 2013. The planting date conundrum for corn, Corny News Network. Purdue University. http://www.agry.purdue.edu/ext/corn/news/timeless/pltdatecornyld.html. Web sources verified 04/15/15 150416083018