Get some mycoroot or similar product for the fungi, its pretty cheap.
Some bonemeal for P, observing leaf branches going purple (when not due to low temps), is normaly a good indication that its time for a bit more... it is good for forming strong roots. Then as the plant starts to flower it will need some more instead of the usual Nitrogen it would need for makeing leaves during veg. This you could get from most of the kelp/seawead mixes out there... also lots of good compost without lots of bark and sticks worked into the soil a bit before you plant so it has time to release some nutrients into the ground.
I realy commend you for thinking of an alternative to ferts.
In my opinion one should grow healthy living soil to grow healthy plants.
Fertilisers pesticides and fungicides, kills the fungi, bacteria and worms that form the basis of the pyramid of life while adding salts until the soil in the long run is unuseable, without major timeconsuming rehabilitation.
You better learn how to work with natural products and sources, because when the oil prices rocket as they will, fertilisers are going to get very expensive.... the only viable commercial source of P is from the oil industry...
P.S. plants just like humans need a lot more than N, P and K to thrive.