Revised Corn Fertilizer Recommendations Improves Profitability by $15 Million

Name and Position/Title:
Brian Lang / Field Agronomist

Fiscal Year Submitted:
2011

POW Title and Number:
100 Corn and Soybean Production

Title:
Revised Corn Fertilizer Recommendations Improves Profitability by $15 Million

Issue:
During the last 50 years a transition to clean coal, less cropland fertilized with manure, and other related crop production issues have greatly reduced the amount of sulfur (S) deposited onto cropland.  Over forty years of prior research in Iowa had rarely noted improved corn yields with S fertilization.  Statewide studies conducted in Iowa from 2000 to 2005 had not found corn yield increases from S fertilizer application.  However, recent research in northeast Iowa documented S deficiencies in alfalfa and significant yield responses from applied S fertilizers (Lang et al., 2006).  During this time of alfalfa research, it was noticed on similar soils that early corn growth was also exhibiting S deficiency symptoms.  The objective in 2007 through 2009 was to investigate the extent of S deficiency in the northeast Iowa geographic area and the potential economic response of corn production to S fertilization.

What Did You Do?
In 2007, the ISU Extension Agronomist in northeast Iowa initiated 16 on-farm S fertilizer research trials on corn across 9 counties in both 2007 and 2008.  Research sites represented a cross-section of different soil types, tillage systems and crop rotations.  Another 20 trials were conducted in 2009, including locations into north central Iowa.  The research uncovered a wide range of corn yield responses to sulfur fertilization, largely dependent on soil type.  Research results provided farmers with the tools to determine sulfur deficiency and the maximum economic rate of sulfur fertilizer to apply.  During these years’ of research, and upon the completion of the research, over 50 ISU Extension educational meetings in northeast Iowa, and extensive use of the media, advanced this knowledge to farmers and agricultural providers.

Results:
Survey results from farmers and agricultural providers in 2008 and again in 2010 documented corn grain yield increases to S fertilization occurred at 71% of the sites.  The frequency was 89% with sandy soils and 64% with loam and silt loam soils.  The average yield increase was 24 bushels per acre on sandy soils and 11 bushels per acre on loam and silt loam soils.  The net economic return to sulfur averaged $70 per acre on sandy soils and $25 per acre on loam and silt loam soils.  This research indicates a change in the need for S fertilization in northeast Iowa, and that S application is an economically viable fertilization practice on many soils.  The potential economic impact of this research for corn production in northeast Iowa approximates $15 million.  This research also spurred the interest of University faculty in neighboring states where they have since initiated similar research.

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