When making a soil, nitrogen, phosphorus, and potassium are normally stressed as the most essential nutrients to the plant. Although these are important, they are not the most important thing to a living soil. A living soil needs sufficient porosity, cation exchange capacity, organic matter, and most importantly calcium. You want a CEC of at least 10 meq and a base saturation of calcium at 85%. It's important for plant health, but all of these factors will make sure that you have a suitable environment for all your microbes to thrive and make sure you can get all the essential nutrients. There are studies where the phosphorus levels are 1000x less than a soil with phosphorus fertilizer, but it was present in the above ground biomass by a factor of 100x because the microbes were able to thrive and deliver the nutrients to the plant.