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Late Planting Guidelines

Ellen Phillips, Extension Educator, Countryside Extension Center, 708-352-0109, ephillps@uiuc.edu

The Illinois Agronomy Handbook provides the following guidelines for late planting. Below are estimated yield losses for corn and soybeans if planting is delayed.

May 1 to May 10 1/2 bushel yield loss per day of delay
May 11 to May 20 1 bushel yield loss per day of delay
May 21 to May 30 1 1/2 bushel yield loss per day of delay
After May 30 about 2 bushels yield loss per day
June 10 3 bushels yield loss per day

Planting in the first half of May generally results in the best yield. Delaying planting beyond the middle of May results in decreased yields, and at an ever-increasing rate as the calendar date gets later. By the end of June, yield potential drops to roughly 50 percent to 60 percent of what could have been obtained with timely May seeding. While delayed planting reduces soybean yield potential; the yield penalty for late-planted soybeans is not as great as that for corn. For late-planted soybeans, consider the following.

  1. Use Mid to Full Season Variety
    -delayed planted fields do not need an earlier maturing soybean variety. Generally, for each 2 to 3 day delay in seeding beyond the optimum planting period only a 1-day delay in maturity will result for the same variety.
  2. Use Narrow Rows
    -results in maximum sunlight interception in a shorter time
  3. Increase Seeding Rate
    • planting delayed to June 10, increase seeding rate by 10 to 15 percent
    • planting delayed to June 20, increase seeding rate by 20 to 30 percent
    • planting delayed to July 1, increase seeding rate by 50 percent