Fertilizer use in Iowa has increased considerably since 1938. Who uses it? When, where, why and how much? Here are the results of a study by Iowa State College and TVA to find more information on users and nonusers.
Anderson, M. A. and Baum, E. L.
"How Your Neighbors Use Fertilizer,"
Iowa Farm Science: Vol. 11
, Article 8.
Available at: https://lib.dr.iastate.edu/farmscience/vol11/iss10/8