Everyone has their sweet spot. I kept pushing for more soil until I hit a point where I found that when I pulled the plants up after the harvest, the roots were not reaching or utilizing all the soil I was giving them, and I was lugging around a lot of water to keep all that soil viable. I had gotten to the point where I shoe-horned a 54 gallon tote into the (less than 2x4) closet I was growing in, it took up almost the entire footprint of the floor space. I could not fit more soil in there without boarding up the bottom of the closet door and just filling the bottom of the closet itself with dirt! LOLnext time around we will be making deep beds for the plants. each one will get like 20+ gallons soil. and there starts notill!!
I'm going to make my bed 14 inches tall in the 2x4so it should easily hold about 8-9 cubic feet of soil...49-56 imperial gallons=O so each plant will get a fuck load and a half. however i will be making it no till so it gonna be a super awesome mix of biologically goodies. i still want to be pulling .5-1pound out of this 2x4 so I'm gonna need all the rootspace i can getEveryone has their sweet spot. I kept pushing for more soil until I hit a point where I found that when I pulled the plants up after the harvest, the roots were not reaching or utilizing all the soil I was giving them, and I was lugging around a lot of water to keep all that soil viable. I had gotten to the point where I shoe-horned a 54 gallon tote into the (less than 2x4) closet I was growing in, it took up almost the entire footprint of the floor space. I could not fit more soil in there without boarding up the bottom of the closet door and just filling the bottom of the closet itself with dirt! LOL
I guess it depends on your system, how you water and how you drain. For me I found the point of diminishing returns, based on how long I veg for and how extensive my roots get. No till is how I garden outdoors, but my indoor garden works on a different paradigm.
I look forward to seeing how yours goes.