I've done something very similar for 20 years now though I DO add purchased microbes too, like those in Primal Defense tablets for people.....all 14 were derived from healthy soil. Did wonders for my Denver and Tampa clients' roses as a one time foliar spray to inoculate the bushes and soil beneath them.

http://www.motherearthnews.com/organic-gardening/probioticsfor-the-soilbrew-your-own-local-indigenous-microbes-zbcz1402.aspx