Agronomically Optimal Soybean Seeding Rates and Associated Risk

In a bean pod:

  • 211 field studies were grouped into similar environmental (soil × climate) clusters and into high (HYL), medium (MYL), and low (LYL) yield levels.
  • Within the two northern most clusters, the agronomically optimal seeding rates (AOSR) were higher in the LYL followed by the MYL then HYL.
  • Within the farthest south cluster, a relatively small (+/-6,000 seeds/ac) change in seeding rate from the MYL was required to reach the AOSR of the LYL and HYL, respectively.
  • The increase in seeding rate to reach the LYL AOSR was relatively greater (5x) than the decrease to reach the HYL AOSR within the northern most cluster.
  • Seeding rates below the AOSR presented a small potential yield loss, while seeding rates above provided slight yield increases.
  • Specific to LYLs and MYLs, establishing and maintaining an adequate plant stand until harvest maximized yield regardless of the seeding rate.
  • The economic optimal soybean seeding rate (EOSR) will be below the AOSR and are based on seed input costs and commodity price.

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