OSU Recommends Not to Increase Corn Seeding Rates for Late Planting

May 13, 2009 at 7:30 am

Rain delays during corn planting are frustrating, especially if rain delays are pushing corn planting into mid- and late-May.  There are a few things that can be done to counter the effects of late corn planting, but increasing the corn seeding rate is not recommended.  Peter Thomison, OSU Corn Specialist discussed the issue in last year’s May 20, 2008  CORN Newsletter:

Past university research indicates that optimal plant populations for early (mid to late April) and late planted (late May to early June) corn are similar. Based on results of these studies, most extension agronomists recommend that final plant populations should not be changed as planting date is delayed. One of the questions I’ve been asked recently is whether seeding rates should be increased for late planted corn. I’m not aware of studies in the Corn Belt that show consistent yield benefits from increasing plant population in late plantings. If planting is delayed until early June, some Ohio data suggests that certain hybrids are more susceptible to stalk lodging at high populations. In a recent OSU study, effects of early (late April) and late plantings (early to mid June planting dates) on corn response to population (24,000, 30,000, 36,000 and 42,000 plants/A) were investigated at three locations. Results suggested that final stands of 30,000 to 36,000 plants/A were required for optimal yield for the late April plantings. However, for the early to mid June planting dates, the results indicated little benefit from increasing seeding rate and a significant yield loss at plant populations above 30,000 plants/A.

In delayed planting situations, use the optimal seeding rates for the yield potential of each field. Recommended seeding rates for early planting dates are often 10% higher than the desired harvest population. However, soil temperatures are usually warmer in late planted fields, and as a result germination and emergence should be more rapid and uniform. So, as planting is delayed, seeding rates may be lowered (decreased to 3 to 5% higher than the desired harvest population) in anticipation of a higher percentage of seed emerging.

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