Central & Northern IL Delayed Corn Planting Recommendations

  • Corn planting in Central and Northern Illinois has been delayed because of cold temperatures and wet soils.  With those delays comes the thoughts of switching to earlier maturity corn products to offset late planting.
  • 13;10;
  • Yield potential can decrease with delayed planting because of a number of factors, including a shorter growing season, insect and disease pressure, and moisture stress during pollination.
  • 13;10;
  • Switching to earlier maturing corn products should not be an automatic decision as full-season products for an area tend to maintain the highest yield potential regardless of planting date as long as black layer can be achieved.
13;10;
Corn Maturity

Careful consideration should be given prior to switching to an earlier corn product. Full-season corn products for a given area typically have the highest yield potential, which may help offset the cost of drying higher moisture corn. As planting is delayed, corn product maturities come closer together. Corn generally requires 1.6 growing degree units (GDUs) less each day to reach flowering and 6.8 GDUs less each day to reach physiological maturity (black layer) as planting is delayed beyond about May 1.1 Therefore, corn planted in late May compared to an optimum date may actually take 110 to 210  fewer GDUs to reach black layer.

When to Switch Corn Maturity

The yield for late-planted corn will vary greatly depending on the remainder of the growing season. The decision to switch maturities can be a difficult one because of variations in growing seasons relative to available GDUs, first frost date, and fall drying conditions. 
digital tool 1
Table 1 provides average available growing season GDU accumulations for various planting dates to average first frost (32º F). As an example, if planting is delayed until the week of May 25 in the Galesburg area, a seed product with a GDU to black layer rating of 2800 can still be planted because its GDU to black layer rating is below the 2949 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 24days)]. 

The numbers provided are based on averages and should only be used as a reference. The main reason for switching to an earlier maturity corn product is not so much for potential yield, but to reduce the risk of immature and wet grain in the fall. Quite often, the increased yield potential of full-season seed products can outweigh the increased cost of drying in the fall. Based on GDU ratings, full-season products for an area can usually be safely planted until the later part of May.  Through the years, plot data has generally demonstrated that high potential yield products, regardless of planting date, remain high potential yield products. Therefore, the decision to switch to an earlier product should not be made quickly.

The best one can do is review long term averages and future forecasts for late planting information.  There have been growing seasons, such as in 2009, that GDUs were slow to accumulate as temperatures remained on the cool side throughout the growing season.  However, that is usually not the case and one must use the long-term averages.  As an example, from April 27 to May 15 at Rockford, an average of 6.9 GDUs accumulate per day.  That increases to 15.0 per day for the period May 16 to June 15, 22.2 per day for June 16 to July 15, 23.2 per day for July 16 to August 15, and 19.2 per day for August 16 to September 15 (Table 2). digital tool 1

The National Oceanic and Atmospheric Administration (NOAA) three-month forecast for May through July indicates a 40% chance that temperatures will be above normal (Figure 1).  This information would indicate that temperatures and GDU accumulation for the 2013 growing season could be above or near normal.  The NOAA cautions that the information should be used only as a guide and not as a high confidence forecast.

Product Considerations 

With insect protection and crop safety becoming more important with later planting, corn with Genuity® traits that offer insect protection and herbicide tolerance, such as Genuity® SmartStax® or Genuity® VT Triple PRO® products or Genuity® SmartStax® RIB Complete® and Genuity® VT Triple PRO® RIB Complete® corn blends should be considered. Additionally, even with delayed planting, it is still important to try and minimize the risk of adverse weather during critical growth stages by planting a package of products that range in GDU requirements to flowering as well as maturity. Selecting products that flower early for their maturity may help reduce the risk of damage from an early frost. digital tool 1

Sources: 1 S. Brouder et al. 2008. Corn & Soybean Field Guide. ID-179. Purdue University. West Lafayette, Indiana.
2 Weather.com. http//www.weather.com. 3 Data provided by the Illinois State Water Survey (ISWS) located in Champaign and Peoria, Illinois, and on the web at www.isws.illinois.edu. National Oceanic and Atmospheric Administration. http://www.nws.noaa.gov.