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Because of April and May rainfall, corn planting was delayed in areas of Central and Northern Indiana. However, late-planted corn can mature reasonably close to earlier planted corn.
Late planting of a full-season corn product does not necessarily result its maturity being greatly delayed. Research has demonstrated that as planting is delayed, the growing degree units (GDUs) required for an individual corn product’s maturity decreases. Corn generally requires 1.6 and 6.8 GDUs less for each day beyond May 1 to reach flowering and physiological maturity (black layer, Figure 1), respectively.1 Therefore, corn planted in late May compared to an optimum date may take 110 to 210 fewer GDUs to reach black layer.
As an example, Table 1 provides average available growing season GDU accumulations for various planting dates to average first frost (32 ºF) for several Northern Indiana locations. If a full-season 2700 GDU product was planted the week of May 25 in the Indianapolis area, it has the potential to reach black layer because its black layer rating is below the 2772 potential. Additionally, a product with a GDU to black layer rating of 2800, planted on May 25, should only require 2637 GDUs to black layer [2800 GDU requirement—(6.8 GDUs less/day X 24 days)]. With this information, a late-planted fuller-season corn product may not necessarily vary greatly in moisture content compared to the same product planted during a “normal�? planting period. The numbers provided are based averages and should only be used as a reference.
Often, it is beneficial to stay with a fuller season corn product because the yield potential of a full season product may outweigh the benefit of switching to an earlier product that may provide drier grain. The best one can do is review long term averages and future forecasts for late planting information. There have been slow to accumulate GDU growing seasons because of cooler than normal summer-time temperatures such as in 2009 (Table 2); however, that is usually not the case. As an example, from April 27 to May 15 at West Lafayette, an average of 8.6 GDUs accumulate per day. That increases to 16.9 per day for the period May 16 to June 15, 23.2 per day for June 16 to July 15, 24.1 per day for July 16 to August 15, and then decreases to 21.0 per day for August 16 to September 15 (Table 2).
Table 1. Average GDU accumulation from various planting dates to average first frost (32 °F) dates in various locations across Northern Indiana.2 GDU Base temperature of 50 °F. Ceiling temperature 86 °F. (30-year average for GDUs); Freeze dates based on 1951-1980 data. 13;10;
Table 2. Average long-term (30-year) GDU accumulations for growing season time periods compared to 2009 for West Lafayette, IN.2 GDU Base temperature of 50 °F. Ceiling temperature 86 °F (30-year average)9;13;10;
1 Brouder, S., et al. 2008. Corn & Soybean Field Guide. ID-179. Purdue University. West Lafayette, Indiana
3 Koss, W.J., Owenby, J.R., Steurer, P.M., and Ezell, D.S. 1988. Freeze/Frost Data. Climatography of the U.S. No. 20, Supplement No. 1. National Climatic Data Center. Asheville, North Carolina.