Changing sprayer fill type

[DanL58]

The Stara Imperador uses both solid and liquid fertilizer. I have a modded version of it but is there a way to change it so that both tanks carry liquid fertilizer or somehow disable the solid fertilizer? A Courseplay bug will not let hired workers use the liquid fertilizer. I tried changing the xml filltypes but then nothing would work, I'm a rookie at editting mods. I know the game also has the Rubicon sprayer but for my farm the Imperator's size and working width would work better.
Thanks