March 20, 2023
- Largely due to the widespread adoption of treated soybean seed, growers increasingly plant soybean seed earlier than in years past. For example, 41% of the Illinois soybean crop was planted by May 2, 2021, compared to the previous 5-year average of 14%.1
- Historically, researchers and agronomists have recommended increasing seeding rates to attain satisfactory yield potential when planting later in the growing season.2 This research was conducted with a goal of understanding the interaction between planting date and seeding rate.
- Another objective was to understand if seeding rate and planting date affect ultimate plant height since taller plants tend to lodge more.
RESEARCH SITE DETAILS
- This research was conducted at Bayer Crop Science FOCUS sites in Woodford County, Illinois from 2021-2022.
- A 3.5 MG soybean product was planted.
- All seed was treated with Acceleron® Seed Applied Solutions STANDARD and ILEVO® seed treatment.
- Standard fertility and weed management practices were followed, and plots were harvested when they reached maturity.
UNDERSTANDING THE RESULTS
- Although yield decreased with later plantings, there was no distinct yield trend associated with seeding rates at any planting date (Figure 1).
- In 2022, final plant height was measured by seeding rate across planting dates. No conclusions about the effect of seeding rate on height can be gained from this research; however, later planted plots tended to be shorter (Figure 2).
Figure 1. Effect of seeding rate on yield potential across planting dates in 2021-2022 at Roanoke, IL. Although yield decreased with later plantings, there was no distinct yield trend associated with seeding rates at any planting date.
Figure 2. Effect of planting date and seeding rate on plant height in 2022 at Roanoke, IL. No conclusions about the effect of seeding rate on plant height can be gained from this research; however, later planted plots tended to be shorter.
- This research does not support the commonly accepted notion that farmers need to increase soybean seeding rates when planting later in the growing season.
- In this study, planting soybean earlier in the season had a greater impact on increasing yield potential than seeding rate decisions.
- Planting date also had a greater impact on plant height than seeding rates for this study.
1Illinois Crop Progress and Condition. May 3, 2021. USDA National Agricultural Statistic Service. https://www.nass.usda.gov/Statistics_by_State/Illinois/Publications/Crop_Progress_&_Condition/2021/20210503-IL-Crop-Progress.pdf.
2Kleinjan, J., Varenhorst, A., and Hauswedell, B. 2020. Soybean planting population: a review. South Dakota State University Extension. https://extension.sdstate.edu/soybean-planting-population-review/.