You don't know if your soil needs it until you have a professional soil test. (The soil hereabouts has plenty.)

It poisons the soil if you put too much on, that's what it does. Otherwise the idea is that it will improve production. But as stated you don't know if it will help your production or not without at least first having an idea how much phosphorus is in your soil already.

My simplified opinion that few areas do really need phosphate, the problem is in what is in the soil exist in such form that does not release easily into plants so by introducing compost and manure we help phosphate to be released as a plant food. And overabundance can be harmful.
Soil test to be done so areas can be identified that are naturally low in P. Another thing to remember it is not only P that might be a problem but other minerals as well as they have relationship where one wonôt work without another.