Sorry but this doesn't appear to be very "in depth" at all to me. While I do agree that a quality pH meter is valuable for dialing in a given grow (mandatory for hydro-grows) it is not necessarily something you can't live without on indoor soil grows and can be downright impractical on outdoor guerilla grows. Trying to measure the runoff-pH on plants grown in native soils would be a neat trick indeed. It may be simply anecdotal evidence but, I've done dozens of grows (indoor and outdoor) without the benefit of said ph meters and they have given me impressive yields by just doing simple soil tests then, by the judicious adjustment of macro-nutrients (less is usually more). As far as the "in depth" portion of this post goes, there isn't the merest mention of something as elemental as a desireable pH range or, the consequences of going too alkaline or acidic (macro/micro "lockout"). Looks more like something cut/pasted from a freshman in high school's horticulture class text book minus the index or footnotes. That was a VERY long time ago for yours truly.