It wouldn't hurt. Personally, I never saw much benefit in using pure potassium. I once used it on the recommendation of Dr Richard Campbell, but I found that getting an exceptional mango crop requires:
- Application of micronutrients 2 or 3 times per year: zinc, manganese, iron, boron, copper, etc
- Application of a high potassium analysis, slow release fertilizer with phosphorus and magnesium, once in the fall and again in the spring. I really like Har's new Fruitilzer formulation, which is a 0-3-16 with minors and slow release K.
- Application of gypsum with the high-K fertilizer. This depends on soil conditions, but gypsum will stave off internal breakdown and help to increase brix. Deep sand and high organic content soils can benefit from gypsum.
- Fungicide if inland.
Lately, I've also been experimenting with potassium nitrate, which is supposed to increase fruit set and retention.
TLDR; version: Potassium by itself is unlikely to be very beneficial unless that's the only nutrient that your soil is lacking in (unlikely). You want to start your fertilization regimen in the fall so that your trees have a bank of nutrients in the leaves by the time bloom starts.
I have a nube question. Should I throw a little 0-0-60 around the trees to help them flower/ push fruit.