A fun experiment with MG or more specifically the time release nutes(those little yellowish/white balls)in basic MG potting mix. You can either pick through a bag of dirt and remove a handful of the fert pellets. Or get a handful of Osmocote slow release from a fellow outdoor gardener. Now puts those pellets in a glass of water. A few may dissolve rapidly but for the most part they will remain balls for many days, even weeks. The majority are coated to be slow released and normal watering only releases a minimal amount of nutes. Yes you can certainly burn a plant with poor watering habits and pre-charged mediums. But I do not think its for the exact reasons most think.........