Considerations for Corn and Soybean Seed Size

Genetic yield potential is not affected by seed size in corn and soybean. However, proper seeding depth, singulation of seed delivery, and spacing affect stand uniformity which can have an influence on yield potential. Accurate planting of various seed sizes is contingent on proper planter adjustments for seed size.

Year-to-year variations and individual seed production environments can influence seed size; however, genetic yield potential is not affected by seed size in corn and soybean. Research across the Corn Belt comparing corn with different seed sizes and shapes indicates that when plant population is similar across different seed sizes, yields are usually the same regardless of the size or shape of planted seed.1 Considering soybean, when seed quality tests indicate no problem with smaller seed, the use of smaller seed shows little, if any, risk.3

Small corn and soybean seed needs less water to germinate, thus emergence may be faster. Also, small soybean cotyledons may be able to move up through the soil during emergence easier as compared to large cotyledons.

To help maximize yield potential, seed selection should be based on agronomic characteristics (disease tolerance, standability, maturity) rather than seed size. Proper planter adjustments should be addressed to plant different seed sizes at the appropriate rate.

Plantability issues can occur if planters are not properly adjusted for the seed size being planted. Improper adjustments can lead to excessive numbers of doubles or skips when planting corn seeds. When planting larger sized soybean seed, under-seeding is more likely to occur than over- seeding, which can reduce yield potential.

Tips for Calibrating Planting Equipment

  • Equipment should be adjusted and calibrated prior to full-scale planting.
  • The seeding rate should be checked in the field by catching the seed coming from the meters when traveling a known distance and counting the number of seeds collected to determine accuracy.
  • Calibration should be based on seeds per foot of row and never on the basis of pounds of seed per acre.
  • Refer to manufacturer and aftermarket manuals for planter calibration instructions and seeding rate charts with specific settings and seed sizes.

Graphite and Talc Use

Using talc, graphite, or a blend of the two can help improve seed flow and drop, especially with high rates of seed treatments and/or humid conditions. Increased rates of talc or graphite may be necessary for the increased surface area with small seed. Talc or graphite should be mixed well throughout the hopper or tank to provide adequate coverage.

For detailed information on planter settings for different corn and soybean seed sizes, visit