By Peter Thomison
Past Ohio State 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 shouldn't be changed as planting date is delayed.
If planting is delayed until early June, some Ohio data suggests that certain hybrids are more susceptible to stalk lodging at high populations. 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.