Thanks, Ken -- I feel pretty comfortable with the fact that it was actually "peat" that I bought, it was definitely compressed and weighed only slightly less than a ton even when it was dry! I cut an opening in the top of the plastic and stuck the hose in to add some water and let it sit for a couple of days to absorb it before I used it to re-do the blueberries, along with some of my own compost and some sulfur and rock phosphate (all recommended on a couple of sites that described how to amend soil for growing blueberries). Guess I should have read that before I put the plants in last year
In my own defense (at least sort of), I thought they would grow here without needing anything special, there are so many wild blueberries in the UP. I'm not at all sure they're going to recover, although I keep trying to convince myself that they look a little better (and at least they haven't died yet); plan B will be to pull them out and plant strawberries in that area!