I remember thinking I was going to need to buy some of those neat Canadian flat sided hoppers, made by ECW at that time, to bring potash to my layout's feritlizer plant.
I was talking about it to a railroad conductor. He said "What year you modeling?" I said 54. He said "Box cars."
Later I found out they also got potash from New Mexico. In one of the photos of the plant you can see a ATSF box car.
Clark Propst