Providing adequate amounts of phosphorous and potassium nutrition can help soybean plants reach their potential yield. When these nutrients are deficient in the soil, the plants cannot reach their maximum potential and it will be reflected in the yield. Dr. Robert Mullen, Director of Agronomy with Potash Corporation of Saskatchewan, explains the importance of phosphorus (P) and potassium (K) in the soil, provides tips for a fertilizer strategy, and discusses why proper plant nutrition is a wise economic decision for farmers.

Key Takeaways:

  • Corn requires more phosphorus while soybeans require more potassium.
  • However, it is just as important to supply phosphorus for soybeans, as they remove as much of this nutrient from the soil as corn does.
  • The “build and maintain” fertilizer strategy is something that farmers should consider because there is a lower risk of the soybean crop becoming nutrient deficient.
  • Build soil test levels to 25 ppm P and 180 ppm K and then maintain those levels by at least matching crop removal rates.
  • To increase P by one ppm in the soil, you need to apply 12 to 20 pounds of phosphate per acre.
  • To increase K by one ppm in the soil, you need to apply eight to 16 pounds of potash per acre.
  • Collect more than enough soil samples to get a representative sample of where nutrient levels are. Even in a small area, phosphorous or potassium levels can vary quite a bit. If you composite sample, sample yearly. If you grid or zone sample, sample every three years.
  • P and K recs may not be enough to keep up with crop removal rates based on today’s corn and soybean yields. That is why it’s so important to soil test frequently and invest in fertilizer.

One CEU in Nutrient Management is available for viewing this webinar.

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