A simple Google search will get you started. I did a 15-week Master Gardener course in Palm Beach County Florida through the Extension Service there. And we learned a lot about soil depletion and health and in that short course. There's no shortage of information available. I'm attending an organic growers conference in North Carolina this weekend and one whole segment of the weekend is on soil health and remediation. It's a complicated subject because some of it also has to consider the depletion of a wide range of minerals complicated by airborne and water runoff toxicities from other participants in the environment.