Northeast Research and Demonstration Farm
Historically, sulfur (S) deficiency has not been an issue for crop production in Iowa. Research results as recent as 2002 on corn and soybeans were consistent with previous results. The exception was a long-standing suggestion to apply S as commercial fertilizer or livestock manure for alfalfa production on sandy soils.
Iowa State University
Pecinovsky, Kenneth T. and Lang, Brian J., "Effect of Sulfur and Boron Fertilization on Alfalfa" (2012). Iowa State Research Farm Progress Reports. 81.