Adjusting Seeding Rates for Low Germination Soybean Seed

Key Points

• To help achieve a desired soybean stand, growers should consider the germination percentage and the average survival rate when selecting a seeding rate. The germination percentage is given on the seed tag.
• Planning, preparation, and management can be used to help reduce the impact of lower seed germination rates.

Soybean Germination and Seeding Rates

The germination rate for a lot of soybean seed is given on the bag or bulk seed tag. It is uncommon for any soybean seed lot to test at 100% germination, so growers should always review the information on the tag when calculating the seeding rate required to help produce the desired final stand. Additionally, growers should consider that even if a seed germinates, it may not result in a harvestable mature plant. On average, the survival rate for a germinating soybean seed is 85%.¹

Growers can use the following calculation to estimate the seeding rate likely to produce the desired stand.

• First, convert the percent germination rate and survival rate to decimals. For example, a 90% germination rate from the seed tag would be 0.90, and the average 85% survival rate would be 0.85.
• Second, multiply the decimal germination rate and survival rate (0.90 × 0.85 = 0.765). This number (0.765, or 76.5%) is the percent of seeds planted likely to result in a harvestable mature plant.
• Third, divide the desired final stand (for example, 100,000 plants/acre) by the decimal number obtained previously to get the seeding rate (100,000/0.765 = 130,719 seeds/acre).

Growers may want to round up the calculated seeding rate slightly (for example, from 130,713 to 140,000 seeds/acre) to provide a buffer to help ensure they reach their desired final plant population.

Additional Management Suggestions

Ensuring that the planter or drill is properly calibrated also helps growers achieve their desired seeding rate. For calibration tips for a small grain drill, click here: https://extension.psu.edu/calibration-of-grain-seed-drills. For a row planter, consult the owner’s manual for proper calibration.

Management strategies to help improve plant survival include:

• The use of a seed treatment can help keep the survival rate as high as possible, particularly when planting into cool and wet soil conditions, or if the field has a history of seedling diseases, particularly Phytophthora.²
• Planting at the recommended depth of one to one-and-a-half inches.³
  • Consider planting at the shallower end of the range with early planting, high residue seedbeds, fine textured soils, or moist conditions.
  • If planting later, in coarse textured soils, or in dry soils, plant at the deeper end of the range.

Impact of Seed Size

Seed size can also be found on the bag or bulk seed tag. While seed size may vary, under most conditions, seed size has no impact on germination or vigor.⁴ Soybean seed products are generally sold by seed count. An average seed size is 2,800 seeds/pound but seed size can vary among seed products. Using the average seed size of 2,800 seeds/pound, a bag of 140,000 seeds would weigh about 50 lb. If the seeds were smaller, say 3,200 seeds/pound, a bag of 140,000 seeds would weigh slightly less than 44 lb.

Sources

¹Specht, J., Thompson, L., Brhel, J., Grassini, P., Glewen, K., and Tenorio, F.A. 2016. Soybean seeding rate tips. University of Nebraska–Lincoln, CropWatch. https://cropwatch.unl.edu/2016/soybean-seeding-rate-tips

²Specht, J., Giesler, L., Wright, R., and Pryor, R. 2018. Q&A: When does soybean seed treatment pay? University of Nebraska–Lincoln, CropWatch. https://cropwatch.unl.edu/2018/qa-when-does-soybean-seed-treatment-pay

³Anderson, E. and Staton, M. 2016. Soybean planting depth matters. Michigan State University Extension. https://www.canr.msu.edu/news/soybean_planting_depth_matters

⁴Wiebold, W.J. 2008. Soybean seed size does not affect yield performance. University of Missouri. https://ipm.missouri.edu/croppest/2008/11/Soybean-Seed-Size-Does-Not-Affect-Yield-Performance/index.cfm

Web sources verified 4/15/25. 1316_105022