I'm not sure what the building codes are in your area, but in our parts:
To properly anchor a deck post, no matter if it's PT or Cedar -
It must be anchored to a concrete footing. If you live in an area of frost, then the concrete footing must extend 4' down below grade. Lately most building depts around here want 12" diameter footings. The Post must then be anchored to the footing using a bolt and bracket system.