Well my 2¢ is yes CO² will increase the yield by at least 30% if you use it right. But you asked about the difference in yield of hydro vs. dirt. The first one is in hydro indoors you can get 3 to 4 crops a year. With some methods you can get 5 or 6 but with dirt most can only get one croup maybe 2 if they are lucky. So is you average the yield over a year. Hydroponics will give you more of a yield. But if you only grow once a year and grow big dirt will give you a lot to. There is one way to grow in hydro that will give you 2-3 pounds from each plant.

That is for pros though the setup cost a shit load to build and run but it will give you the most bang for the buck itâ??s called KBS growing. The setup is 15k to 20k to do it right with about 20 plants.