We seem to be pretty well agreed in Iowa that it pays to use commerical fertilizers. But a lot of us are still trying to find the right ones to use for the right crop. We are still not certain as to HOW to use fertilizers to get the most from them.
Nelson, L. B.
"Let's Use Fertilizers Right,"
Iowa Farm Science: Vol. 3
, Article 2.
Available at: https://lib.dr.iastate.edu/farmscience/vol3/iss7/2