Considerations for Double Crop Soybean Production

With both wheat and barley harvests underway, it's time to consider strategies for a successful double-crop soybean planting. The main factors for maximizing yield and profitability are: plant thick, plant narrow, use longer-maturity varieties, and manage weeds proactively.

Currently, soil moisture levels are adequate, and additional rain is in the forecast. In many cases, soybeans planted immediately after barley have emerged quickly following rainfall. However, this is not always the case.

Soybeans typically require around 90 days to reach pod development and seed maturity. Given average frost dates in Pennsylvania, soybeans should ideally be planted by July 15, and no later than August 1 to ensure maturity before the first frost. According to frost maps, some areas of Pennsylvania experience their first frost around November 1, offering a slightly longer planting window in those regions.

Plant Population

• Target a final stand of at least 180,000 plants per acre (ppa).
• Seeding Rate Recommendations:
  • 200,000 ppa if planting before July 5.
  • 220,000 ppa if planting after July 5, to support rapid canopy closure and maximize light interception.

Row Spacing

• Utilize narrow rows—preferably less than 15 inches, with 7-inch spacing ideal.
  • Narrow rows increase light capture and support pod development, especially critical when reduced plant height is expected in late-planted soybeans.

Weed Management

• If weeds are present at planting, apply a burndown herbicide to reduce early-season competition.
  • Timely weed control promotes better stand establishment and early vigor, which is essential for double-crop systems.
  • For more on soybean weed management, read Small Grain Harvest and Double Crop Soybeans. 

Economic Considerations

• Set realistic yield expectations.
  • Typical double-crop soybean yields in Pennsylvania average around 30 bu/acre for early July planting.
  • Yield potential declines by approximately 50% by mid-July.
  • In high-performing fields, yields up to 60 bu/acre have been recorded, demonstrating the variability in return on investment.

*Relevant to areas with viable double-crop potential.
Data compiled from Ohio, Indiana, Minnesota, and Pennsylvania.

Frost Risk and Forage Alternative

• Be mindful of early frost risk with late plantings.
• If forage production is a higher priority, consider alternative crops such as sorghum-sudangrass or other summer annual forages that may offer better biomass and harvest flexibility.

Maturity Group Considerations

• While some recommend shifting to shorter-maturity varieties, local experience in Pennsylvania suggests that full-season maturity soybeans often outperform short-season selections in double-crop settings.
  • For example, in 2023, Lancaster County double-crop soybean trials planted on June 24 at 220,000 ppa averaged 54 bu/acre under wet conditions.

Maturity Timing Insights (Based on Dr. Holshouser, Virginia Tech):

• Select varieties that maximize vegetative growth before flowering to enhance canopy development and yield, while still maturing before the first frost.
  • In April and May plantings: a 3-day planting delay results in a 1-day delay in maturity.
  • In June and July plantings: a 5-day planting delay only causes about a 1-day delay in maturity.

This video, Effect of Planting Date on Double-Crop Soybeans, discusses the project and provides a view of the different planting dates in the field.