i have done an experiment side by side same strain same soil same nutes same lighting re using soil has NO benenfits IMO I I use promix and I have been reading on the whole reusing soil so I went and dug out all the old roots and anything remaining of the old plant matter and I ran the blueberrydisel plant along side of the other 5 in new promix soil first thinng is first it is almost 1/3 smaller than all the other plants the old soil definately stunted the growth rate the bud sites are slower to fill in that its counter parts and the soil also retains more moisture for some reason, the only benefit I see is that the trich production is higher than the other 5 bud the buds are noticably smaller so smaller buds for more crystal ? Maybe if that's what u want b not me lol so as for reusing soil goes HELL NO just get new dirt. And I used the old soil in the plant from veg through till flower there is no benefits . IMO