What is the shelf life of Miracle-Gro powder?
My dad has accumulated about 15-20 lbs of powder Miracle-Gro fertilizer from various auctions he's gone to in the past few years. Most of them have been opened, and he's stored them down in our cellar (~65F year-round and high humidity). I'm pretty sure that the nitrogen present in them has broken down, but by how much? Some of these may be a decade old by now. The potassium and phosphates remain the same over time, though, right? If nothing else, I was planning on slowly adding it to the compost pile so that it gets put to use.