Residual N Availability Advice after Hail in Soybeans

Joel DeJong, Crops Field Specialist, Northwest


Just before the end of the growing season in NW Iowa, two different hail storms made a path of destruction through NW Iowa. Three weeks later, before frost hit, these fields had a perfect stand of new soybean seedlings because a high percentage of soybeans in many of these fields shattered out of their pods, came into contact with the ground, and germinated. It really looked pretty, except we knew that this meant many bushels of soybeans that were unable to be harvested. However, there is nitrogen value in those soybeans, so it was possible to reduce N applications to corn for the next year based on what was in the soybeans.

Research had been done by John Sawyer and Paul Kassel in a similar situation from Clay County just a few years ago. With this information, and data a Minnesota study that looked at yield response in corn when fertilized with soybean meal, I could share the that for every 10 bushels of beans on the ground our data would indicate that we could reduce N applications for corn in the following year by 25#. See the ICM Newsletter article by Dr. Sawyer from 2002: . I utilized this information to answer many phone calls, present at meetings, and share in the media and in my Crop Update newsletter, trying to get producers to take credit for the N supplied by the soybeans.

I contacted several producers who had contacted me, or that received my newsletter and lived in that hail belt to see if they were reducing N rates for next years corn crop based on this information. I received 12 responses to this informal survey, and found that these producers were going to reduce N rates by 20 80# per acre. There were 3234 acres where they were going to make this management change. Total value of the nitrogen reduction, based on $.33/pound N was just over $48,000. I visited with many more, and lots received this same information from agronomists in NW Iowa that were quoting this data. The impact of reducing N in this situation was quite good.
Having a researched data base for situations like this can really give me the confidence to make good recommendations, and gives the producers confidence to follow them.

February 6, 2006
103 - Nutrient Management

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