I would think 3 to 4 days to dry out the soil if you have good air flow. Just dig down a couple of inches along the sides as far from the roots as possible, If you have 2 inches of dry soil, then you are due for a watering in the next day or 2. you will get used to knowing when to water as you get to know your grow. I believe that PH is important, but mostly for non-soil grows. but of course, the more dialed in you are, the more chance of a great crop. JUST MY 2 CENTS WORTH