m0useanswered grow question 10 days ago One of my products for myco's needs to be in contact with the roots like others are saying.
The other product I use is one where it is dissolved into the water then watered in. Most of the stuff on the market is selling spores and CFU, so its can be mixed into the top of the medium and watered in. the spores that hit the roots will germinate and be suscessful.