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New Mobile Corn Replant Decision Aid

Dennis Bowman
June 7, 2013
Recommended citation format: Bowman, D. "New Mobile Corn Replant Decision Aid." Department of Crop Sciences, University of Illinois at Urbana-Champaign, June 7, 2013. Permalink

Deciding on whether or not to replant can be a difficult decision. Cutworm, compaction and seedling blight are some of the problems that can lead to reduced plant populations. The sight of an uneven reduced stand is often more than many farmers can take, but the desire to “fix-it” may not make sense agronomically or economically.

For fields where the stand has been relatively evenly thinned out the following advice is most relevant. Where flooding or ponding has completely wiped out a stand in large areas the decision to replant is easier but may be difficult to execute until these areas have fully dried out.

To make a more objective decision, start with an accurate assessment of the current plant population. In the past we recommended that you use Table 2.3 on page 24 of the Illinois Agronomy Handbook (corn chapter). This chart provides the percent of maximum yield for various planting dates and populations. The Agronomy Handbook is available on-line at  This table will assist you in comparing yield potential of an early planted crop with reduced population and a late planted stand with optimum population.

To make this a little simpler we have created a mobile calculator that looks up the information for you. All you have to do is put in:

  • Realistic optimum yield for the field
  • Original planting date
  • Current plant population
  • Replant planting date
  • Corn price

The calculator utilizes the formulas that were the basis of the original Agronomy Handbook table and compares the replant yield potential with that of the existing stand. It quickly provides you with a dollar per acre amount you can use to determine if there is a economic incentive to replant and if the difference will be enough to cover replanting expenses.

The replant calculator is available as:
Android app:
IPhone/IPad mobile spreadsheet:

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