When Should I Switch to an Earlier RM Hybrid?


  • The 2019 planting season was severely delayed across much of the Corn Belt. Most of the corn crop in Illinois was not planted until after June 3rd.

  • Farmers are asking for guidance around when they should consider switching to an earlier relative maturity (RM) hybrid to mitigate the risk of a killing frost before the corn crop could mature.

  • The Bayer Learning Center at Monmouth, IL conducted a trial to evaluate the difference in yield and return over drying cost among a range of RMs planted on two different dates in June.



LocationMonmouth, ILPlanting Date6/3/19, 6/11/19
Soil TypeSilt loamHarvest Date10/28/19
Previous CropSoybean Potential Yield (bu/acre)250
Tillage TypeConventionalSeeding Rate (seeds/acre)36K
  • Six different corn products ranging from 95- to 114-day RM were planted on two different dates in 2019:
    • June 3rd
    • June 11th
  • All plots were harvested on October 28th and adjusted to 15% moisture. 

  • Yields were calculated and compared as was return over drying cost.


  • Yields were consistently higher in the June 3rd planting with the exception of the 108-day corn product (Figure 1).
    • Even though this product yielded higher in the later planting, higher drying costs led to the earlier planting date being more profitable.
  • Moisture was substantially higher across all plots planted on June 11th (Figure 1).

  • Return over drying costs declined substantially from the June 3rd to June 11th planting date (Figure 2).

    • However, returns for the later RM corn products were still higher than the two earliest RM corn products.



  • Corn products that were earlier in maturity than the typical RM range for the area (105- to 115-day RM) did not yield or return well compared to the corn products that fit the area in a ‘normal’ growing season.

  • These results suggest that while switching from late-maturing to earlier-maturing hybrids may be justified by the 2nd week in June, farmers should still consider staying with a RM that fits their geography.

  • Growing conditions are highly variable form year to year. Consult your local Technical Agronomist or Field Sales Representative for specific recommendations for your farm.

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