Whether gypsum, or land plaster, which was quite widely used as a fertilizer in Europe 150 years ago and later in the United States, can be profitably used on Iowa soils is the interesting question with which the experiments reported in this bulletin have to do.
As yet no final answer can be given, but this much can be said on the basis of this experimental work; Gypsum applied to some Iowa soils gave some beneficial results in oat and red clover yields and very decidedly good results in alfalfa yields. Gypsum supplies a large proportion of sulfur as well as calcium and when any crop such as alfalfa requires these elements applications of gypsum may prove profitable. This is especially true of Iowa soils, many of which arc deficient in sulfur. Further, gypsum is an Iowa product, conveniently at hand and can be produced economically. The experiments suggest definitely that it is worth the while of Iowa farmers to try out this material on a limited scale.
Erdman, L. W. and Bollen, W. B.
"Field experiments with Gypsum in Iowa,"
Bulletin: Vol. 19
, Article 1.
Available at: https://lib.dr.iastate.edu/bulletin/vol19/iss232/1