Longitudinal Study: Investigating the Planting Date’s Effect on Soybean Yield Potential in the Northern Plains

Key Findings

The optimum planting date to maximize soybean yield potential has a larger time frame than corn.
10+ years of data supports the widely accepted practice of planting soybean early in the growing season, and waiting for more favorable conditions to begin planting corn (See A Long-Term Research Study Investigating the Effect of Planting Date on Corn Yield Potential and Moisture Content in the Northern Plains).
The potential to maximize yield at 100% is reduced by 1.0% per day after May 25. Individual locations and years may vary — this data should be used as a guide of recommendations on optimum planting dates.
Individual locations and years may vary — this data should be used as a guide of recommendations on optimum planting dates.
Typically, soybean seed can be planted when soil moisture conditions are satisfactory, regardless of soil temperature and forecast.

Understand the risks and rewards of planting soybeans at different times throughout spring.
Provide guidance on when to plant in order to maximize yield potential.
Help growers make informed replant decisions when stands are reduced by frost or other stressors.

Ongoing trial conducted in the Northern Plains (North and South Dakota) since 2010.
Data summarizes a smaller data set with limited locations. Values are based on averages and not significantly analyzed.
While comparing data across years, findings are presented as a percentage of the maximum yield for the year and soybean product.
Non-replicated strip trial design.

Late April to mid-May proved to have the highest yields, with a steady decline as the season progressed (Figure 1).
The potential to maximize yield decreased 20% from May 25 to June 15 (a span of 20 days), producing an average daily loss of 1.0% (Figure 1).

Figure 1. After May 25, the potential to maximize yield decreased by 1.0% per day (as shown via arrows).