
Certified GKH Gardening Expert
I would not reuse potting soil for starting seeds. Fresh potting soil will work better and eliminate any chance of bacteria or other contamination that may be present in your old potting soil. I put my used potting soil into compost, or sometimes dig it into my garden beds if I"m sure it's clear of problems. Here's an article about how to sanitize your potting soil:
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/sterilizing-soil.htm