Economic analyses of crop response to fertilizer, together with the degree to which other good management practices are used, make it possible to show more than one profitable fertilizer rate for soil samples tested.
Stritzel, J. A.
"You Have a Choice of Fertilizer Rates,"
Iowa Farm Science: Vol. 17
, Article 6.
Available at: https://lib.dr.iastate.edu/farmscience/vol17/iss12/6