Since you don't know where to buy gypsum and you are not marking the exact locations of your beds - I assume your soil test good for ginseng without adding any supplements.
If my soil did not need ammending I would not be marking the exact locations of my beds either.
mhowa - I checked the Lowes over in Columbia TN and they have 10 lb bag of gypsum for 9.99. They said they will have some 40 lb bags in before spring but the guy I spoke with was not real sure what the price was.
I found a usagypsum supplier online (see link above) where you can get it at reasonable price for the material, but the shipping is quite expensive (18.00 per bag) ouch.
The pulverized gypsum at 3.95 per 50 lb bag should do nicely, but then agian the shipping will sure increase the cost.
If you ordered more than 10 bags sounds like it could be shipped differently and they would give you a freight quote.
I may have to call them and just see what the freight cost might be on 20 bags of that pulverized gypsum product. That would be 1000 pounds and that would last me quite a while.
It would sure be nice if there was a local supplier where you could get it at that price without the shipping.