It is dominantly used as a fertilizer for crops which include tobacco, some vegetables, and fruits. Potassium sulfate is used as a salt substitute. It is used in artillery propellant charges as a flash reducer. It is used in soda blasting.
Potassium sulfate is often preferred over potassium chloride for some chloride-sensitive crops such as potatoes, tobacco, some vegetables and fruits, some tree crops like almonds, walnuts and citrus, although these sensitivities are highly dependent on growing conditions, soil salinity, and salinity and chloride in …

Here are some tips for using sulphate of potash:
Apply every 4–6 weeks to maintain plant quality.
Avoid getting fertilizer on leaves and stems, as it can cause leaf burn or damage.
Shake off excess fertilizer from leaves and stems.