Late Planting Corn Considerations

By: Harold Watters, Ohio State University Extension

With some “late” planting some folks are concerned already about whether or not we might be caught by a fall frost before maturity without a change in maturity selection. Not to worry. The corn plant has the ability to adapt to the later planting by advancing more rapidly through the growth stages. Work done at Purdue and Ohio State by graduate students of Bob Nielsen and Peter Thomison, show that the number of growing degree days (GDD) needed from planting to maturity decreases by about 7 GDD per day of delayed planting. As a result, a hybrid planted on May 30 needs about 200 less GDDs to achieve maturity than a hybrid planted on May 1.

Is there a reason to plant shorter season hybrids in Ohio? Yes, maybe. Peter Thomison has been looking at early maturing hybrids in Ohio as a way to get corn off early, maybe to have dry corn for early markets, or to harvest early to have a place for late fall forages. How early can we go? Ask your seed person, I did last summer and was told to be very careful as when you bring a hybrid too far south, it is out of its adapted zone and likely to fall prey to disease and stress it normally does not see.

Poor stands

What are some of the factors that may contribute to poor stands? The use of shallow tillage tools (work at soil depths of about 4 inches or less) following a wild winter with limited freezing and thawing may have added to existing compaction. Also, some fields were compacted last fall during harvest. Finally, add a couple (or three or four) of heavy rainfall events this spring and you have multiple factors that will contribute to loss of soil structure with associated soil compaction.

Other possible contributing factors to the corn stand loss in these fields include:

1. Rotation; limited rotations without wheat or forage and in some cases multiple year soybeans now followed by corn.
2. Organic matter (OM) of soils in some areas of the fields was less than 2% with a corresponding low CEC. Low OM soils may be more prone to crusting and compaction.
3. Use of pop-up fertilizer applied on corn seed at planting. Applying fertilizer to the seed is not a recommended practice. However, if it is done, for soils with CEC greater than 7, the maximum salt index is 8 (lbs of N + K₂0).
4. Herbicide injury. For example, products containing cell growth inhibitors may under certain environmental conditions injure corn seedlings.
5. Insect injury. Various insects such as wireworms, seed corn maggots, grubs, and others have the ability to reduce plant stands.
6. Corn seedling diseases caused by various pathogens.
7. Malfunctioning corn planter regarding seedling depth, fertilizer delivery, and more.

The above factors may have been exaggerated by the late winter, and sudden onset of summer. The week before we started planting in earnest, I had snow at my house. Was the soil really as warm as we wished when planting started?