I'd probably go for option 4 - don't use it on the spud beds. It's quite alkaline, which will risk causing the condition scab on the surface of the spuds. They will still be edible, just look scabby.
But if you do use it for potatoes, I'd probably do option 1. Least effort!
If you chose to use it for something like courgettes instead, I'd do option 3 - add it to the planting hole.