Revise Alfalfa Fertilizer Recommendations to Adjust to a Changing Environment

Name and Position/Title:
Brian Lang / Field Agronomist

Fiscal Year Submitted:

POW Title and Number:
103 Forages, small grains and new opportunities

Revise Alfalfa Fertilizer Recommendations to Adjust to a Changing Environment

Over the last 50 years a transition to clean coal, less cropland fertilized with manure, and other related issues have greatly reduced the amount of sulfur deposited onto cropland.  Over the last 10 years, as corn and soybean yields continued to increase, farmers often commented on only obtaining average alfalfa yields.

What Did You Do?
In 2005, Iowa State University Extension in northeast Iowa initiated an investigation into this issue.  Since alfalfa production requires significantly more sulfur than most other crops, it was possible that previously researched soil fertility recommendations needed to be adjusted.  Fifteen research trials conducted over the next 4 years as both on-farm trials and at the northeast ISU research farm uncovered sulfur deficiencies in alfalfa production in most fields.  Research results provided farmers with the tools to determine sulfur deficiency and the maximum economic rate of sulfur fertilizer to apply on these sulfur deficient sites.  During these years of research, and upon the completion of the research, over 75 Extension educational meetings in northeast Iowa advanced this knowledge to farmers, agricultural providers and through the media. 

Survey data from farmers and agricultural providers in 2008 documented that 57% of the alfalfa fields in northeast Iowa were now receiving sulfur fertilizer applications and increased farmers’ net profit of $57 per acre.  A follow-up survey in 2010 documented that 72% of alfalfa fields in northeast Iowa now receive sulfur fertilizer with farmers’ increasing their net profit by an average of $52 per acre over alfalfa production prior to sulfur fertilizer usage.  Farmer comments about the improved production with sulfur fertilizer included: “This was a God send.”, “You really made me money!”, “It made a hell of a difference.”, “I was ready to tear up the stand, but it (the sulfur) let me keep it (the stand) 2 more years.”  With approximately 200,000 acres of alfalfa in northeast Iowa, this response equates to an economic improvement of about $7.5 million.  The research was also shared with University faculty in neighboring states where they initiated similar research.


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