I got the FULL treatment by the TSA my last time out of CLT, as they had detected “explosive” residue about my carry-on bags and/or body. It only occurred to me later that my last stop before the airport had been an SC horse farm.
In any case, as I had plenty of time before my flight, I didn’t mind it so much except to be asked if I was a “gun advocate”, to which I replied, “Yes, I’m a Second Amendment advocate, but I don’t have any weapons with me.”
That one really shocked me a bit.
Probably fertilizer residue. Easy to pick up on your shoes if you walk past a recently fertilized garden or visit a gardening center where they sell bags of fertilizer.