Mycorrhizae........because they just work........... the results and benefits are REAL.
Also.........
Volcanic rock dust.......excellent source of trace minerals
Bone meal.......excellent source of slow release calcium
Insect frass.........excellent source of auxins and other bio stimulants
Worm casts..........just wonderful
Bio char..........excellent source of carbon
Aged chicken manure.........excellent source of nitrogen
Kelp meal..........excellent source of potassium
Aged cow manure..........great for soil structure and soil fertility
Compost, compost compost!