I would likely re-use it, if only a month old, no sign of disease, or insects ... keep in mind, the residual fertilizer that may already be in the soil ... normally, after a full grow, I dump it out, start with fresh ... to be safe, used potting soil should be rinsed, dried, baked, to kill any insect eggs, or organisms, etc. ... a major pain in the ass, so I just fork out the $$ for new soil ... use your judgement ... :smokin: