By Jonathan Kleinjan
Due to the late planting season in 2018, growers are becoming more and more worried about potential yield losses due to planting delays. Yield reductions may become significant after about May 20, especially for full season corn hybrids, and the risk of increased drying costs and crop losses due to an early fall frost also become a concern.
Full season corn hybrids have the greatest potential for maximizing yield. However, increased yield potential comes with increased weather risk. Early to mid-season corn hybrids will likely out-perform late-season hybrids if planting is delayed past about May 15. Fourteen years of data from the Southeast Research Farm in Beresford, SD shows that yield reductions typically begin around May 20th for an early corn hybrid (101-103 RM) and around May 5th for a late corn hybrid (112-118 RM). Data from this study is summarized in Table 1.
Table 1. Percentage of maximum yield by planting date for early and full season corn hybrids in Beresford, SD.
| Relative Maturity | Average planting date |
| 17-Apr | 27-Apr | 7-May | 17-May | 27-May |
| Early (~102 RM) | 98 | 100 | 99 | 100 | 90 |
| Full (~115 RM) | 99 | 100 | 97 | 90 | 75 |
| Average | 99 | 100 | 98 | 94 | 82 |
That being said, research from Ohio State and Purdue University show that corn hybrids can ‘make up ground’ when planted later in the season. For example, a hybrid that is rated at 2800 GDDs to black layer when planted at a normal planting date (late April to early May) may require only around 2600 GDDs to black layer when planted in late May or early June. This phenomenon has been noticed in the upper Midwest as well.
The Bottom Line
- It’s too early to consider switching hybrids, especially if you are planting early or mid-season maturities.
- Consider switching to slightly earlier RM (i.e. from 100 to 95 day) after about May 25.
- Reevaluate hybrid maturity selections again about June 5. Consider planting a hybrid with even earlier maturity (i.e. 90 day).
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