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.
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:
The seeding rates/acre were:
There were two replications for each treatment.
Plots were kept weed-free.
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.
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 results suggest that:
The optimum soybean seeding rate is highly variable from year to year.
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