I never, ever, use chemical ferts outside. Amendments, microbes, and time, are all you need. It's really selfish, in my opinion, to burn all the surrounding vegetation, load the ground with salts, fuck the natural ph of the soil, and kill all the microbes that call it home; just to grow some plants for yourself.
Just mix up a batch of super soil (with no rock phosphate ever as it can poison water supplies [probably not the right term, but I don't care]), dig a really deep and wide hole, then fill it with your super soil, and plant. It's called super soil for a reason lol. That's all I do, and water with teas (one for veg, separate recipe for bloom), and I've never grown a plant I am not proud of.