The very act of gardening changes the natural balance of the soil, but without doing that we would be very limited as to the things we could grow. I think what you're reading is similar to the argument that taking vitamin pills provides things the body needs, but may reduce the bodies capacity to produce them itself from ingested food. My opinion of what 'organic' gardening means is using no artificially manufactured chemicals such as pesticides and herbicides, but those made from plants are OK. In practical terms, to increase soil fertility organically means making your own compost and adding animal manure, which is high in Potassium and Phosphorus (ie K and P.) The N (Nitrogen) will come from anything green you place in the compost. Dead material such as dry leaves and stems provides almost nothing in terms of nutrients, but improves soil structure. Growing a large clump of comfrey, harvesting it several times a year and adding it to your compost heap is an excellent way to get the Nitrogen, as well as providing several trace nutrients comfrey extracts from the subsoil via extremely deep roots. It is the naturally occuring bacteria and fungi in your compost heap which break down organic matter and release N, P and K.
I'm not sure if that answers your question either, though.
