Originally Posted by WannaBeOrganic
I think it means exactly what it says. If there is enough phosphorus in the soil, the plant will grow deep roots to get it. If there isn't enough it will attract mycorrhizae to help it get what phosphorus is there.
I don't think she says that the plants are better off without mycorrhizae but it doesn't need them depending on the level of P. If you have plenty of P in the soil then the plants don't excrete the acid that attracts mycorrhizae so buying mycorrhizae to innoculate the soil would be a waste of money.
What seems like it might be interesting is if you start off providing enough phosphorus. This will cause the grass to work on bigger/deeper roots. This will help keep it looking better in the summer heat. Then let the phosphorus drop so mycorrhizae can colonize the roots. Now you have the previous root growth and mycorrihizae working together. ....
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?