Many an Iowa farmer is aware that some day he may need to use commercial fertilizer, especially phosphate, in order to produce crops satisfactorily. He wonders, "Has that time arrived? Could I profitably increase my crop yields by applying fertilizer?"
Englehorn, A. J.
"The Case of Phosphate Fertilizer,"
Farm Science Reporter: Vol. 2
, Article 3.
Available at: https://lib.dr.iastate.edu/farmsciencereporter/vol2/iss4/3