Some things to consider when planting corn in May

Jim Herbek and Chad Lee, Extension Agronomists, University of Kentucky

The following was taken from the most recent Corn and Soybean Newsletter on corn planting dates.

Use a corn hybrid with the Bt trait for corn borer. University of Kentucky research shows a yield benefit and an economic benefit to Bt corn borer hybrids planted in May. The later the planting date, the greater the yield benefit for the Bt hybrid.

Possibly switch to an earlier-maturing hybrid. Based on calculations of growing degree days remaining in an average season, hybrids with relative maturities of 118-day (and less) will reach physiological maturity (black layer) before frost in west Kentucky even if planting is delayed until late May. For late May plantings in central and eastern Kentucky, hybrids of 116-day relative maturity or less are likely needed. If planting occurs in early to mid-June, then a switch to hybrids of 113 to 116-day relative maturities will likely be needed. For extremely late plantings (after mid-June), hybrids of 110 to 113-day relative maturities or less are needed.
Keep the seeding rates and row spacing the same. Two exceptions: if someone convinced you to try 38,000 seeds per acre, try it in a small area instead of a large field. Your odds of getting decent yields from late plantings are good, but your odds of getting excellent yields are not.

Keep the seeding rates and row spacing the same. Two exceptions: if someone convinced you to try 38,000 seeds per acre, try it in a small area instead of a large field. Your odds of getting decent yields from late plantings are good, but your odds of getting excellent yields are not.

If you have the ability to plant narrow rows or twin rows, the late planting date could make for some excellent comparisons. We know that going to narrow rows in late-planted soybeans improves yields. Perhaps the same could occur in corn. Some on-farm comparisons would be excellent. One caution here: setting up a really good comparison takes time, and when fields are suitable for planting again, you won't have much time.

For more information on corn planting date and hybrid options, refer to publication AGR-195: Replanting Options for Corn that includes a table on Kentucky location, planting date, and expected date to reach black layer (physiological maturity) for three hybrid maturities.

For more questions about corn planting dates, contact your local county extension agent.