This is not new information but I was not aware of it till a few months ago, so I thought I would post a link here. The article in short is saying when planting woody perennials(trees and shrubs) not to amend the soil, but instead to use mulch on top. http://www.sustainablehorticulture.com/myth-soil_amendments.pdf
I am not so sure this applies to Blueberry bushes! They have special needs! They like acidic
soil, and I have read the best thing to plant them in is a pine bark mulch. I would recommend doing specific research on planting Blueberry bushes.