Inspired by Mark L. Staker's article on Newel K. Whitney ("Thou art the man", BYU Studies 42.1 (2003), pp.75ff0, which talks about the ashery in Kirtland, I was trying to find some of the "ashery manuals" that Staker talks about, but could only find a 1917 JSTOR article on the relative contribution of wood and plant material to the overall The Production of Potash in the United States.
I also found a comparable one for Canada, equally from 1917. One suspects that the preparations or munition supplies for WW1 are implicated here. For a worldwide view with Western focus in 1922, see Potash.
A somewhat similar article for the 1880s is on Potash in the Far West, but that already includes Utah of course.