Indiana Late Corn Planting Recommendations

  • When corn planting is delayed, farmers may consider switching to earlier maturity corn products to offset late planting.
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  • 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. 
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  • 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.
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Corn Maturity

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Careful consideration should be given prior to switching to an earlier-maturing 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.   

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When to Switch Corn Maturity

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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. Table 1 provides average available growing season GDU accumulations for various planting dates to average first frost (32ºF) for various locations across Northern Indiana. As an example, if planting is delayed until the week of May 25 in the Indianapolis area, a seed product with a GDU to black layer rating of 2700 can still be planted because its GDU to 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)]. The numbers provided are based on averages and should only be used as a reference.   

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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 value of 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 be carefully considered.   

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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 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).    

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With insect protection and crop safety becoming more important with later planting, corn with traits that offer insect protection and herbicide tolerance should be considered. Additionally, even with delayed planting, it is still important to try to minimize the risk of lost yield potential due to 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.   

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 Table 1. Average GDU accumulation from various planting dates to average first frost (32oF) dates in various locations across Indiana.2
 Planting Date
 Wabash
Columbia City 
 West Lafayette
South Bend 
Indianapolis 
Shelbyville 
 Columbus
Terre Haute 
 Washington
Evansville 
 April 27
2691 
2614
3095 
2746
3045 
-- 
-- 
 --
 --
-- 
 May 4
2658 
2587
3048
2716 
3000 
-- 
-- 
 --
 --
 --
 May 11
2608 
2544 
2985 
2670 
2939
 --
-- 
 --
-- 
-- 
 May 18
2543
2485
2907 
2609 
2863
2983 
3097 
3303 
3474 
3454 
 May 25
2461 
2410
2813 
2533 
2772 
2877 
2994 
3192 
3355 
3328
 June 1
-- 
 --
 --
-- 
-- 
2761 
2876 
3065 
3216 
3190
 June 8
-- 
 --
 --
-- 
 --
2628 
2742 
2921 
3062 
3042
 June 15
 --
 --
 --
-- 
-- 
2481 
2592 
2761 
2896
2877 
 June 22
 --
 --
 --
 --
-- 
2321 
2428 
2588 
2720
2706 
 Ave. 1st Fall Frost (32oF)
 Oct. 5
Oct. 11 
Oct. 12 
Oct. 18 
Oct. 20 
 Oct. 24
Oct. 24 
Oct. 24 
Oct. 24 
Oct. 25 
 GDU base temperature of 50oF. Ceiling temperatue 86oF. (30-year average for GDUs) Freeze dates based on data from 1952 - 2012.
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 Table 2. Average long-term GDU accumulations for growing season periods of time compared to 2009 for West Lafayette, IN.2
 Growing Season Time Periods
 Long-Term Average
 Long-Term Average/Day
 2009 Accumulation
 2009 Variance
April 27 to May 15 
163.5 
8.6 
175 
11.5 
May 16 to June 15 
525 
16.9 
518 
 -7.0
June 16 to July 15 
719 
23.2 
700 
-19.0 
July 16 to August 15 
746
24.1 
677.5 
-68.5 
 August 16 to September 15
 652.5
21.0 
592 
-60.5 
 GDU base temperature of 50oF. Ceiling temperature 86oF. (30-year average)
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