Growing blueberries in bales of peat, you mean with the plastic still holding the bales together? A common medium for potting blueberries is 50-50 sand and peat but with a wetting agent in the mix because peat moss tends to repel water. Of course, using a 50-50 mix of peat and soil is often recommended for establishing blueberries in most soils. Its drawback is that the peat usually only takes a short time to decompose once well incorporated in aerated soil so the benefit of its acidity declines in time if not augmented with sulfur.
[NAFEX] blueberries in bales of peat,
Alan Haigh, 10/26/2008