judging by your name you're in southern az area and the soil there is great for cannabis there with only minor help...when i lived and grew there i'd dig out a roughly 2 x 2 x2 hole for each plant then mixed half n half with quality potting soil. they will be needing lots of water during the heat of summer so if you want the big plants you'll have to water em up to 3x/day...

good luck