Outdoors, there probably isn't anything better than natural soil -or what I would call dirt. You can add manures, meals, compost, worms, fungi, etc.....and it will just keep getting better and better as time goes on. It will balance itself....
...however, indoors is a whole different approach. I don't believe there is as much of a benefit to attempting to bring all of the outdoor "stuff" indoors. You don't have Nature assisting you when you grow indoors. YOU are Nature! YOU are the one who needs to take care of any and all pathogens that might arise indoors. It becomes a "sterile" environment, indoors, where the entire focus is on growing the plant and not on chasing after pests, predators and pathogens -especially in small grows such as tents and closets. In such condensed settings, pathogens can get out of hand very quickly. If, for example, you get mites indoors, then you can't rely on ladybugs to get rid of them. In addition, predatory bugs also poop all over the plants, too. You don't have any rainstorms to wash it all off....not to even mention how much pollution that rain water has in it (in populated areas). Don't believe me? Collect a jar of rainwater sometime and just look at it!...but I digress....
For me, indoors is all about cleanliness -"laboratory conditions." It allows me to grow inside my house without creating any secondary problems. "Synthetic" fertilizer may be interpreted as something bad because of how we, as humans, perceive the idea of eating synthetic food. A better word (in my opinion) would be "molecular" fertilizer -because all the NPK has been broken down to molecules that are instantly available to the plants.
Outdoor growing relies on God's input. Indoor growing...
I am God!
