There are already good references in previous threads (e.g. look up anything by Gabe Brown). But in a nutshell - plants are in a symbiosis with the microorgani

There are already good references in previous threads (e.g. look up anything by Gabe Brown). But in a nutshell - plants are in a symbiosis with the microorganisms and fungi that live in the ground. Plants feed them sugars and they feed the plants nutrients in return. When you add large amounts of artificial fertilizers, plants don't need to feed these organisms anymore and this soil fauna dies. But the soil fauna also normally excretes materials that improve soil quality (e.g. fungi excrete glomalin, which binds the soil particles together). So if you use artificial fertilizers for a long time, your soil becomes dead. And such soil is easily depleted by wind and rain erosion.