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Soybean Planting Rates

~ This weeks blog brought to you by Dwight Willoughby and Derek Erb~

Establishing healthy, uniform stands are important to maximize soybean profitability, even though soybeans respond to reduced stands by increasing lateral branching.  Optimum conditions may be needed to reach max potential in years with reduced stands.

Factors that can impact plant survival vary each year and every farm has different risks they are willing to take on.

Factors Affecting Soybean Seeding Rate

  • Soil Type:   Soils with high clay (our area) often remain cool and wet favor certain seeding diseases such as Phytophthora and Pythium.
  • Soil Residue:   Fields with lots of residue will keep the soil cooler and wetter again favoring slow emergence and increase risk of seeding diseases.
  • Planter vs. Drill:  Typically planters do a better job of seed placement increasing plant counts and uniformity.  Manitoba Pulse Growers uses a factor of plant survival of 82% with a planter and 72% with a drill.
  • Row Width:  Higher seeding rates have traditionally been recommended for narrow-row soybeans.
  • Planting Date:  Early planting into cool wet soil typically means slower emergence and again increase risk for seedling diseases.  Late planting increase planting rate would limit branching and hopefully reduce maturity.

Manitoba Pulse Growers recommend a harvestable plant count in the fall of 140,000 – 150,000 plants per acre to reach 100% yield potential.  Under ideal conditions emergence is around 85%.   Under poor conditions (one of multiple of the factors above) survival rate can drop to 50-65%.  Doing final plant counts at seeding and harvest are critical to establish a benchmark for your operation.  You may find you are wasting money on over seeding or losing yield from too low of planting rates.

Calculating Seeding Rates (Manitoba Pulse Growers have an excellent smartphone app for this).

Decide what your final stand target is, then account for actual seed germination and your emergence factor.

Seeding Rate = Targeted final stand / (% germination x % emergence)

Example 1

Farmer using a drill on 15″ rows planted in Mid May targets final stand of 140,000.  Seed tag indicates 90% germination and he is planting in good conditions with a drill, his calculation would be:

140,000 / (0.90 x 0.72) = 216,000 seeds/acre

Example 2

Same conditions and seed lot as above, but using a planter on 15″ row spacing and same target population.  Seed rate calculation is:

140,000/ (0.90 x 0.82) = 189,700

Summary

  • Manitoba Pulse Growers recommend a final plant count at harvest of 140,000 – 150,000 plants/acre.
  • Critical to do plant counts on your farm so you can determine (aside from seed germination) what final plant count success rate is on average.
  • Adjust seeding rates when conditions are not ideal.
  • Soybeans are very resilient and can compensate for lower plant populations however the growing conditions have to play big role capturing a profitable crop.

2014seedingrates

As you can see over 60% of the soybeans planted in Manitoba (of farmers surveyed) are planted over 170,000 plants/acre.

Make it a point to talk to us about what your targets are and be sure to do the counts in the spring and again at harvest time.  It takes time and effort to do these counts but well worth the investments.

Like Will Rogers said, “Good judgement comes from experience and a lot of that comes from bad judgement.”

 

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