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Too Early to Plant Corn?

April 4, 2003

It's tempting . . . soil conditions in much of eastern Illinois are dry enough to be in the fields doing fertilizer application and secondary tillage, and now that the calendar says it's April, thoughts turn to planting corn. Here are some thoughts and observations on whether or not we "pull the trigger" and get the crop in the ground sooner rather than later:

  1. When it's fit to plant this early, it usually is a signal that there will be more than the average number of days suitable for planting over the next month. There are no guarantees on this, but when the soils are already dried sufficiently this early, rainfall is less likely to saturate the soils over the next month, even if April rainfall amounts return to normal after a dry March.
  2. Very little chance exists that corn planted this early will yield more than corn planted the second half of April. Last year, corn in most of central and northern Illinois planted in mid-May yielded more than corn planted in April. This was because of the low temperatures during the third week of May that affected emerged corn and also because of rainfall in late July and early August that greatly improved yields of later-planted corn that was just pollinating. This pattern of temperatures in 2002 was unusual, but it can happen.
  3. The use of Intellicoat seed coating, which is designed to keep corn seed from taking up water until soil temperatures are above a minimum, might make early-planted corn "behave" like corn planted later, but there's no guarantee. We used it on corn planted in early April at two locations in Illinois last year, and with the warm soil temperatures in mid-April, the coating did not delay emergence. Last year, corn planted in mid-May experienced colder soil temperatures for a week after planting than corn planted in early April, but the coating did not affect emergence or yield at any of the planting dates at either location. The coating has a cost, of course, and it is not clear whether this type of "insurance" can be expected to pay its way on a routine basis.
  4. Replanting remains one of the best "insurance" options for early-planted corn, especially if replanting seed is available at little or no cost. Replanting of corn planted early in April, if needed, can usually be done near the "ideal" time to plant corn, which we consider to be late April. You might check out the corn replanting calculator that is part of the Web-based Illinois Agronomy Handbook at to see what the yield and cost consequences of inadequate stands might be.
  5. There can be consequences of applying soil insecticide and some herbicides this early since we expect them to stay active longer than many of them probably will.
  6. Whether or not you choose to plant this early should be influenced both by how many days of planting you have and by your personal approach to risk. For a producer with the "median" 5 or 6 days of corn planting, chances are that it can begin in mid-April and be completed on time.
  7. Finally, no reason exists to rush through corn planting so that soybean planting can begin yet in April. Our studies over the past two years show clearly that soybeans do not benefit from being planted in April and they can suffer decreased yields if planted in early April. May is the month to plant soybean in Illinois.--Emerson D. Nafziger

Author: Emerson Nafziger

The Pest Management and Crop Development Bulletin
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