I don't use often, but do spread some of Excalibur's 8-3-9 (for fruits trees), only use this on my mangos after harvest. this year I did buy a bag of potassium sulfate, and just spread some yesterday.
this year I have been experimenting with foliar spray, this really seems to make a notable difference, on my smaller trees, new leaves are huge, my dragon fruit have kicked into high gear, growing and new branching. I use bioAg Cytoplus, with Dyna grow Pro Tekt (Silica ), and used yucca as a sticking agent.
Cytoplus:
Guaranteed Analysis: Boron (B)...............0.25% Manganese (Mn)..........0.8% Soluble Potash (K2O)......7.5% Cobalt (Co)........... 0.035% Molybdenum (Mo)........0.05% Copper (Cu).......... 0.13% Sulfur (S)......................3.25% Iron (Fe).................0.9% Zinc (Zn).......................0.5%Non-plant food ingredients: Humic Acid(s) 47% , Seaweed Extract 25% (derived from Ascophyllum