A lot of things can make the difference between a good and poor corn crop. Some you can control - others you can't. Here's a roundup of present "know-how" about the factors you can't control.
Dyas, E. S.; Bodensteiner, L. J.; and Anderson, M. A.
"How to Grow Corn,"
Iowa Farm Science: Vol. 6
, Article 3.
Available at: https://lib.dr.iastate.edu/farmscience/vol6/iss10/3