yup the failure of mycorhizae to germinate and prosper when there is enough readily available P around is a very telling story in itself.
Actually, I don't understand humics much at all yet, except that they are extremely complex and variable in their configurations, and the product of biological action in the soil. So if you perchance know of texts that explain this in more depth, and ideally (ok thats probably going too far
) not just myopically chemically but within an functional/ecosystemic perspective, I'd love to read up on those!
As for differences between indoor and outdoor, I totally agree there are differences, but am not at all so sure they're so massive in principle as to be complete game changers
Cheers!