The practice of early-season soybean [Glycine Max (L.) Merr.] planting has been increasing in the northern US. However, a wide range of planting dates (PDs) are still implemented due to poor soil conditions, inclement weather, equipment restrictions, crop rotation, and operation size. Information regarding how soybean management decisions should be adjusted based on PD is lacking in Michigan and other northern US regions. This research was conducted to identify how optimal soybean seeding rate (SR), seed treatment (ST) use, and variety maturity group (MG) selection is determined by PD. Field experiments were conducted at two locations in Michigan during the 2018 and 2019 growing season. In the first experiment, soybean was planted at five SRs, between 123,553 and 518,921 seeds ha-1, with or without a ST, on four PDs (late-April to late-June). In the second experiment, six soybean MGs, between 1.0 and 3.5, were planted on four PDs (late-April to late-June). The use of a ST did not improve yield or net returns in this study. When soybean was planted before mid-May, seed yield and net returns were maximized by planting a late MG (≥3.0) at a SR between 187,660 and 201,451 seeds ha-1. The optimal SR between the mid-May and early-June PDs was between 220,301 and 265,305 seeds ha-1 and MG selection had less influence on seed yield compared to earlier PDs. When planting was delayed to late-June, using an early MG (≤ 2.5) resulted in the optimal yield and the optimal SR was >330,000. Results from this study show that soybean yield, quality, and net returns can be improved by adjusting management practices based on PD.
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