adding mycorrizhae to soil plugs?

For seedlings you want to mix mycorrhizae in the growing media and apply it in the planting hole on every transplanting. It’s very important to inoculate the plants from the earliest stage possible, so the fungi grow on the young roots early on and start to work their magic when the plant needs them most!

Do it. The sooner you can get the fungi to attach to the root system the better.

That's teh right time to do it... myco that matters only survives with roots... so having them colonize early will have the best resutls. some level of phosphate, i believe or potassium, does likely kill or severely reduce the myco... This is why it's doubley useless in a soilless/hydro context - soilless uses hydro nutes which is 100% plant available and ready to use, so no need for anything to be altered or processed by myco or microbe for the plant as it is in soil with certain forms of fertilizer and soil amendments that require such things before a plant can use it. So, a little early... then maybe put some more at transplant. Don't need much early, but maybe a bit more later.. pop it all around where the plug will reside.. perfect placement for new roots to be colonized. Once colonized the rest just happens. even if you didn't asdd some at transplant, it'd probably fill in on it's own, but if you dolled out instructed amount for size of pot, it'll be good... just use a small bit of that dose early. the rest later... no OD / waste,,, assuming instructions are proper relative to size of pot used. each product has different spore counts, so it'l vary as to what dose you need for "optimal", whatever that may be. just math...

I put them in Grodan (rock wool) today to speed up the clones, as I said, if they don't have roots, it's useless, but once they start to make them, it is... the clones have just started to develop their first roots...

Just to prevent confusion; my question is about soil plugs or cubes. Not soil itself.

Im by no means a master frower but its been my experience with yesting soils out that the soil i put mycorrizhae in as a root stimulator and oxygenation aid seems to FLOURISH during veg state so much so that i had to lst the plants from hitting lights, so id say 100% yes, add away.

the mycorrhizae help the roots absorb (simplified) the nutrients for the plant in exchange for carbohydrates. according to tests (done by professionals), it helps a lot, shortly after germination when the first roots start to form. the seedlings absorbed nutrients via the roots earlier than those without.