November 30, 2020

Is soybean seed size an issue?

20130423_agriculture_063 cmopQuestions arise annually regarding the effects of soybean seed size. Keep the importance of seed size in perspective when selecting bean varieties. Yield potential, disease tolerances, and agronomics should be the most important selection criteria.

Seed size: Cause and effect

Soybean seed size is influenced by genetics, but the environment during seed fill can be a major factor. Small and large seeds of the same variety have the same genetic material and therefore, the same yield potential. In most conditions, size doesn’t affect emergence or yield potential.

  • In adverse conditions that delay emergence (cool soil temps. or excessive planting depths); large seed may be able to survive a longer time prior to emergence due to having a larger energy reserve. Planting beans 1” – 1.5” deep into soils that will consistently be warmer than 60 degrees F, can be beneficial. When planting smaller soybean seed, you should consider planting closer to 1” deep, if field conditions and soil moisture allow. Regardless of seed size, it is not recommended to plant less than 1” deep. Small seed requires less energy to emerge from the soil, due to the size of cotyledons being relative to seed size.
  • Smaller seeds require less moisture for emergence and in limited moisture situations this may be an advantage.

Importance of Variety Selection

Soybean variety selection is a critical part of maximizing yield potential. Some key selection properties to consider in order of importance include varietal yield potential, disease tolerance, relative maturity (RM), plant height, and standability.

  • Yield Potential: variety should have high yield potential across multiple conditions in your region
  • Disease Tolerance: diseases such as cyst nematode (SCN), brown stem rot (BSR), sudden death (SDS), & late season phytophthora do not have rescue options and are best managed by variety selection.
  • Relative Maturity: to reduce the risk of potential weather during pod fill, and help maximize yield potential with fuller season varieties, a range of RM can be selected.
  • Plant Height and Standability: fields with high fertility, short or medium plant height with good standability can help reduce lodging concerns. While in less fertile soils, taller plants often set pods higher, which allows for greater harvest efficiency.

In Summary

Soybean seed size will vary in variety and years, based on genetics and weather during pod fill.  Variety selection should be based on yield potential and agronomic characteristics, not seed size.

Soybean seed may be smaller than normal for this planting season, but this should not hide the importance of selecting varieties based on performance when it comes to making soybean variety purchasing decisions.

Always consult your agronomy specialist regarding seed selection for your operation.

 

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