DuPont Pioneer provided basic soybean field fertility principles to remind agronomists and crop consultants about recommendations that should be made to farmers. The information was put together by Keith Diedrick and Steve Butzen.

They provide tried and true information but don’t give concepts on how to push soybeans to major yield increases through fertility. Most of the information associated with soybean research does not show the definitive link of extreme yield to completely new practices in soil fertility.

A summary of Diedrick and Butzen’s extensive explanation of fertilizing procedures and soybean growth is as follows:

  • Soil testing every three to four years is recommended as a basis for managing soybean fertility.
  • Soybeans thrive in the pH range of 6.0 to 6.8. Essential nutrients are readily available and N-fixing rhizobia are favored in this range.
  • N fertilization rarely results in agronomic or economic yield increases when nodulation is normal. More research is needed to determine when N fertilization may be warranted.
  • P and K must be at high enough levels in the soil to prevent soybean deficiencies. Fertilization beyond this “critical” level generally does not increase yields.
  • Sandy, low organic matter soils may show sulfur deficiencies. Atmospheric deposition of sulfate from coal-fired power plants reduces deficiencies in some areas.
  • Manganese deficiencies are most likely to occur in coarse, dry, high pH and high organic matter soils. Soil or foliar applications can be used to provide this nutrient.
  • Iron deficiency chlorosis is associated with native high pH soils. Variety selection is the first and most important step in managing this problem.

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