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Corn products have an ability to respond to a range of planting dates. Research conducted by Ohio State and Purdue University found that the response of corn to delayed planting was a gradual shortening of the time spent in vegetative growth.1 Corn products compensated primarily by shortening the time necessary to reach the silk stage when planting was delayed.
The yield for late-planted corn will vary greatly depending on the rest of the growing season. The decision to switch maturity with delayed corn planting is difficult because of variations in growing seasons relative to available GDDs, the first frost date, and fall drying conditions. Planting into wet soils can result in uneven planting depth and seedling establishment, poor root development, or sidewall compaction. The potential yield loss from these conditions can outweigh the delay in planting until conditions are suitable for good stand establishment. Mid-May planting dates can still have enough potential GDDs for corn to reach physiological maturity without switching to an earlier product maturity.
Since the accumulation of GDDs early in the growing season is low and corn requires fewer GDDs to reach maturity when planted after May 1, it is not recommended to consider switching relative maturities until late May. In general, changing corn relative maturities should only be considered after the third or fourth week of May for much of Michigan.1 Table 1 lists average accumulated GDDs, at several locations over several weeks, based on an April 28th planting date This information can help with the decision of when to switch to an earlier maturity by determining the potential GDDs remaining from a given planting date to typical maturity or killing frost in a given area. Table 2 shows average first frost dates for some cities in Michigan.
For example, consider if planting was delayed until the week of May 15 in the Three Rivers area. In that time, 105 GDDs would have been lost from April 28. If the first average killing frost date is October 23, the maximum potential GDDs remaining for Three Rivers is 2508.5 (2613.5-105). Therefore, a product with a GDD to black layer rating of 2500 GDDs can still be planted because its rating is below the 2508.5 estimated GDD potential that may occur before the first killing frost. If the reduced GDD requirement after May 1st is also taken into consideration, the product is even less likely to encounter a killing frost before physiological maturity:
The numbers given are based on averages and should only be used as a reference. Growers must decide what is best for their operation. Remember that the main reason for switching corn product maturity is not so much for yield, but to reduce the risk of immature and wet grain in the fall.
Insect protection and crop safety become even more important with later planting. Corn with Monsanto traits that offer insect protection and Herbicide tolerance, such as SmartStax® RIB Complete® for the and Genuity® VT Triple PRO® RIB Complete® corn blends, should be considered. Additionally, even with delayed planting, it is still important to try to minimize the risk of adverse weather during critical growth stages by planting a package of products that range in GDD requirements to flowering as well as maturity.
Relative maturity is one of many factors to consider when choosing a corn product for your farm. Switching corn products may reduce the risk of immature and wet grain in the fall. Keep in mind, conditions during the growing season and harvest are other important factors in corn maturation and kernel moisture at harvest. In general, changing corn relative maturities should only be considered after the third or fourth week of May for much of Michigan.
Table 1. Average GDD accumulation from five locations in Michigan, based on an April 28th planting date. Source: The Weather Channel Interactive, Inc. 2013. Growing degree calculator. http://weather.com
Table 2. Median first frost (28° F) dates in Michigan derived from 1981-2010. Source: Midwestern Regional Climate Center. 2017. Freeze maps. Date of first 28° freeze. http://mrcc.isws.illinois.edu
1Nielsen, R.L. and P. Thomison. 2003. Delayed planting and hybrid maturity. AY-312-W. Purdue University Extension.
2Thelen, K. 2009. Exercise patience in deciding when to commence field operations. Integrated Pest Management Resources. Michigan State University. www.ipmnews.msu.edu.
4Nielsen, R. 2009. Late planting & relative hybrid maturity decisions. Purdue University Extension. www.argy.purdue.edu. 170509091156 050917TAM