How Increased Seeding Rates Can Help in Wet Soil Conditions

2021 TRIAL GOALS

Excessive moisture at planting time followed by dry conditions can occasionally cause soil crusting during the spring. This challenging environment can be especially difficult for obtaining a consistent soybean stand.

The objective of this study was to determine the potential benefits of increasing soybean seeding rates to increase stand establishment and subsequent yield potential in challenging, wet field conditions.

RESEARCH SITE DETAILS

Location	Gothenburg, NE
Soil Type	Hord silt loam
Previous Crop	Corn
Tillage Type	Strip-tillage
Planting Date	05/28/21
Harvest Date	10/05/21
Potential Yield (bu/acre)	80
Seeding Rate (seeds/acre)	See below

STUDY INFORMATION

The study used a randomized split-plot design with four replications where soybean seeding rate was the whole plot and soybean product was the sub-plot.
Seeding rates (seeds per acre):

40,000, 80,000, 120,000, 160,000, 200,000 and 240,000

Soybean products:

2.5 maturity group (MG) XtendFlex® soybeans product
2.7 MG XtendFlex soybeans product
2.9 MG XtendFlex soybeans product

The study was irrigated throughout the growing season.
Fertilizer (pounds per acre) applied through strip-tillage prior to planting included 60 pounds of phosphorus, 25 pounds of sulfur and 0.25 pound of zinc. 
Weeds were controlled uniformly across the study
Figure 1 provides an overview of the weather conditions prior to, during and after planting.

Excessive rain occurred prior to planting on May 28. Soil conditions were wet, but planting was pushed in order to move planting along. The closing wheels on the planter may have caused some compaction over the seed furrow. After the 0.6 inch of rain on May 30, minimal rainfall occurred in June. During the first half of June, daily high temperatures climbed into the 80s 90s and even low 100s, with daytime relative humidity as low as 19%, which led to significant soil crusting over the seed furrow. Thinly planted beans had a more difficult time emerging, while soybeans planted at a higher population were able to push through the crust together.

Figure 1. Weather conditions at the Gothenburg Learning Center from May 15 to June 30, 2021.

BREAKING DOWN THE NUMBERS

Soybean grain yield was positively impacted by increased seeding rate (Figure 2).
The 40,000 seeds per acre seeding rate resulted in the lowest average yield among the six seeding rates (Figure 2).
The 80,000 and 120,000 seeds per acre seeding rate resulted in similar average yields, which were 82% and 98% greater than the 40,000 seeds per acre seeding rate, respectively (Figure 2).
The average yield in the plots with the 160,000 seeds per acre seeding rate was 46% and 34% greater than the 80,000 and 120,000 seeds per acre seeding raterespectively (Figure 2).
The average yield in the plots with the 200,000 and 240,000 seeds per acre seeding rate reached statistically similar grain yields and were 21% and 36% greater compared to the 160,000 seeds per acre seeding rate, respectively (Figure 2).
Representative pictures (Figure 3) show the difference in the soybean stands of the 2.5 MG soybean on September 21, 2021.

Figure 2. Average soybean yield resulting from six seeding rates at the Bayer Water Utilization Learning Center in Gothenburg, NE.

Figure 3. Comparison of 2.5 MG soybean stands at planting rates of 40,000, 80,000, 120,000, 160,000 and 200,000 seeds per acre on September 21, 2021, at the Bayer Water Utilization Learning Center in Gothenburg, NE.

SUMMARY OF RESULTS

Here are some key takeaways from this study:

Higher soybean seeding rates (e.g., 200,000 and 240,000 seeds per acre) resulted in increased grain yield and should be considered when planting under tough/wet conditions in the spring. Other research from Gothenburg on soybean seeding rate indicates the optimal seeding rate should be 160,000 seeds per acre when the seed is planted in more favorable soil conditions.
Farmers should work with their local seeds sales team members to help identify the best adapted soybean product for their production systems.