Look into running a combination of humic acid and kelp extract. It has everything you need for root health in soil. Natural PGR's, cytokines, vitamins and enzymes. Humic acid is optimal food for microbial life.
Most people use a ratio of 5:2 humic acid to kelp ratio. There's a lot of studies and anectodotal evidence supporting this. It's even more effective as foliar spray. A combination of the two should be even better. I still use in veg running hydroponics.