Soybean Seeding Rate by Planting Date

TRIAL OBJECTIVE

  • Previous work at the Bayer Learning Center at Monmouth, IL has shown that planting date is an important factor affecting soybean yield potential.

  • In most years, an earlier planting date could be a low-risk/high-return soybean management practice.

  • A generally recommended practice is to increase soybean seeding rates when planting occurs later in the season.1,2 

  • In 2019, the Bayer Learning Center at Monmouth, IL conducted a trial to determine if seeding rate influences the average yield of soybean across multiple planting dates.  

     

RESEARCH SITE DETAILS

Location Monmouth, IL Planting Date 4/24/19, 6/3/19
Soil Type Silt Loam Harvest Date 10/15/19
Previous Crop Corn Potential Yield (bu/acre) 80
Tillage Type Conventional Seeding Rate 40k. 80k, 120k, 160k
  • Two Roundup Ready 2 Xtend® soybean products with relative maturities (RM) of 3.4 and 3.6 were planted on two planting dates at four different seeding rates.

  • The planting dates were:
    • 4/24/19 (early)
    • 6/3/19 (late)
  • The seeding rates/acre were:
    • 40,000 
    • 80,000 
    • 120,000  
    • 160,000 
  • There were two replications for each treatment.  

  • Plots were kept weed-free.

UNDERSTANDING THE RESULTS

  • The soybean plant is rather versatile in its growth and development. As plant population decreases, the plants tend to branch and develop additional nodes to attempt to compensate (Figure 1).

Figure 1. Plants tend to develop additional branches and nodes as seeding rates (population) decrease.
  • The yields of the two soybean products for each planting date were averaged together because the yields of each were very similar. 

  • In this trial, the April 24 planting date favored lower seeding rates, while the June 3 planting date favored higher seeding rates.  

    • This response is in line with university recommendations.1,2
    • However, the higher overall average yields for the June 3 planting date are not typical of previous Bayer Learning Center results.  Extreme weather conditions during the growing season may have contributed to this result.
  • Return over seed cost was maximized at the 80,000 seeds/acre rate for the April 24 planting date, while 120,000 seeds/acre provided the highest return for the June 3 planting date.

    • These calculations assumed a soybean price of $9.50/bu and a seed cost of $69 for a 140,000 unit of seed.
Figure 2. Comparison of average soybean yields for two planting dates and four seeding rates at the Bayer Learning Center at Monmouth, IL in 2019. The early planting date was April 24 and the late planting date was June 3.

KEY LEARNINGS

  • These results suggest that:

    • Early planting of soybean may help maximize profitability. Early planting assumes that the soil and weather conditions are suitable for seedbed preparation and seed germination.
    • Late planting may require increased seeding rates to help optimize yield and profit potential.
  • The optimum soybean seeding rate is highly variable from year to year.

Contact your local Field Sales Representative or Technical Agronomist for planting recommendations for the current situation and year. 

 

Sources:

1Staton, M. 2019. Late-planted soybean recommendations. Michigan State University Extension. https://www.canr.msu.edu/.

2Nafziger, E. 2019. Early-season soybean management for 2019. The Bulletin. University of Illinois. http://bulletin.ipm.illinois.edu/.

Web sources verified 10/29/19. 3011_R1