Impact of Late Planting on Soybean Yield in Southern Illinois

Background and Objectives

  • Many growers are sometimes faced with the decision to plant soybeans at very late dates during the growing season.
  • Yield of late-planted soybeans can be impacted by the shortened growing season, dry soil conditions, or freeze injury.
  • Late planted soybean showing freeze symptoms.

    Study Description

    • A survey was conducted of 158 soybean locations in southern Illinois, planted between July 15 and August 17, 2015.
    • Grower location, soybean maturity, planting date, planting rate and grain yield data were collected.
    • Yield results were analyzed using linear regression on planting date; also grouped into planting date ranges and mean separation analyzed using Student’s t-test.


  • Yield was significantly different among all planting date ranges (Figure 1).
  • Yield declined an average of 1.3 bu/acre per day when planted after July 15 (Figure 2).
  • Soybeans planted in August suffered freeze injury at several locations, which resulted in significantly reduced yield or no yield in some cases.
  • Soybean yield grouped by planting date range. Means with different letters were significantly different at P less than 0.001.
    Linear regression of soybean yield on planting date among 158 grower fields in Southern Illinois, 2015.

    Authors: Eric Alinger and Kirk Reese, DuPont Pioneer. Emerson Nafziger, University of Illinois.

    The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation. 2015 data are based on average of all comparisons made in 158 locations through August 17, 2015. Multi-year and multi-location is a better predictor of future performance. Do not use these or any other data from a limited number of trials as a significant factor in product selection. Product responses are variable and subject to a variety of environmental, disease, and pest pressures. Individual results may vary.