Rhodes Research and Demonstration Farm
Today’s high-yielding soybean varieties respond favorably to early planting. Multi-year results from statewide university research farms suggest that mid-April to early May planting dates produce top yields in most comparisons. Research farm and on-farm strip trials also suggest that elite varieties yield similarly over a wide range of seeding rates and resulting harvest populations. Based on these results, producers are advised to plant soybeans as soon as spring field conditions allow, with a seeding rate of 150,000 to 175,000 seeds per acre.
Iowa State University
Lundvall, John; Whigham, Keith; Westgate, Mark E.; and Farnham, Dale E., "Planting Date and Seed Treatment Effects on Soybean Yield" (2001). Iowa State Research Farm Progress Reports. 1825.