I'd have to check the label, but I'm fairly certain most (if not all) Miracle Grow soils contain fertilizers. Any bag of soil that claims to feed for up to 3 months is prefertilized, and can make it difficult to determine how much and when a supplemental fertilizer is needed. Don't get me wrong, MG is perfectly capable of producing a good harvest, but I prefer not to use it because of the unpredictability of those time-released ferts. If it's all ya got, you can definitely make it work. I'd just recommend adding at least 25% perlite to loosen it up. If you'll be using other nutrients on top of everything else, doing a light flush with clean pH'd water once a month isn't a bad idea... but not always necessary.