Originally Posted by Smallaxe
Yes, I agree that that is what is being said. It makes sense, however - Deeper roots with a fresh app of P at the surface? P does not move through the soil at all - Correct?
That article was about gardening and not lawn care so it is possible that bone meal would have been used at the time of planting or as an amendment that was thoroughly mixed into the soil.
It also didn't provide a high level of detail. It would be nice to know at exactly what level of P does grass work on root growth and when it attracts mycchorziae.
Also, is there some type of balance where you can get both. Mycchorziae colonization can help plants absorb water and nutrients better but is it sometimes better to have deeper roots instead? During the summer where you have greater evaporation of water from the soil, which one is better?
Mycchorizae help with disease resistance as well but there are other ways to accomplish that.
I haven't really had the time to look into much of this yet, maybe others have the answers to these questions. So weather you need to buy and add P is unknown to me but it seems clear that you don't need to inoculate the soil mycchorizae unless it doesn't contain any, which seems unlikely especially if the soil is organically managed. If the plants need mycchorizae they will attract and feed them which will cause them to multiply.