Are you working to break your previous yield records? If so, you’re probably asking what role fertility plays in helping to reap the rewards of a stronger soybean management system.

To help growers make better decisions about soybean fertility needs, ISA recently hosted a summit on the use of nitrogen in soybean production. Participants in the day-long discussion included key soybean researchers from universities and industry partners, as well as ISA directors and local agronomists.

The heart of the question, “Can Illinois farmers expect to see a yield response to supplemental nitrogen?” still remains unanswered. Complicating the answer is a disconnect between the nitrogen (N) needed to support higher soybean yields and the inconsistent response to additional nitrogen in field trials.

Researchers cited several examples showing that the amount of nitrogen removed by a 60 bu/A yield clearly exceeds the amount that can be fixed by soybean nodules and that soybeans do not leave residual nitrogen for the next corn crop. Yet, field trial results are often inconclusive regarding whether to apply N or not on soybeans.

While further research is needed, here are some ideas to help with your fertility plans for 2014:

Key Takeaways:

  • Always look at the overall system to be sure that no factors other than N are limiting.
  • Supplemental nitrogen typically is not needed for yields in the 60- to 70- bushel range.
  • High-yielding beans (greater than 70 bushels) may need supplemental nitrogen because the nitrogen needed by the plant will exceed the amount available from fixation.
  • Early N applications may inhibit nodulation, so current research is looking at 60 to 70 pounds of urea or UAN (urea ammonium nitrate) per acre with a urease inhibitor at the R3 stage—when N demand begins to increase and N fixation begins to wane.
  • More research is needed before best management practices or recommendations on applying N are finalized.
  • Due to environmental concerns around nitrogen on corn, use caution before making added nitrogen a standard practice on soybeans.

The full report and speaker presentations from the nitrogen roundtable are available here.

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