Seems some main issues with reusing soil come from salt-buildup and pests/disease (as already mentioned). Both can be treated bleach treatment and flushing.
I reuse my outdoor garden soil all the time
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i agree everything is recycled but things like absorbancy issues mayerials breaking down perlite looses density and absorbs salt, peat becomes denser and deteriorates looseing airation and absorbancy making ph more likely to fluctuate
to name a few
but don't get me wrong i understand the need to reuse everything possible
replacing soil is just a fairly inexpensive way to help insure a good outcome
one thing i would advise is conditioning soil to sterilize is using hydrogen peroxide solution to do so
bleach is a sodium based product prone to residue salt on material and even w/ good flushing the materials absorb into pourous materials
i recondition soil and have done it for years but i wouldn't tell someone else due to an issue i can't see w/ my own eyes:no:
hydrogen peroxide will help to break down and release salt build up w/ a little surfactant added
i would atleast recomend mixing old reconditioned soil to some new soil and some dolimite
i would also point out whatever sterilizer choosen if beneficial bacter was used in the soil it will be destroyed and should be re-administered
if you find yourself in a pinch and have tested some bud but it had alot of fert taste flush soil w/ hydrogen peroxide added to water it is cheap and easy to use
it will help flush soil and release contaminates and is at a relatively low cost is trying to hurry a harvest