Is it ok to reuse soil after harvesting a plant? If so, is there anything I need to do to it?
i re-use my soil i just give a flush then re-use for next grow - i do not do anything special - might add extra perlite and the harvested stalks / stems if in that mood for extra aeration for roots
You can. Although if you're using synthetic fertilizer then you could encounter salt build up in the medium. You may want to give it a good flush before using again. I recommend amending the soil with an organic fertilizer but you could technically feed synthetic fertilizer right off the bat.
@Mr. Grow It an article or video on how to amend soil for re use would be awesome!