Improving soil addresses the self-sustaining health of plants, making soil sufficiently rich that eventually plants get all the nutrients they need in a natural and sustained manner. Clearly, soil improvement makes more sense and is more cost efficient for a successful, long-lived reclamation effort. They dissolve rock particles and release nutrients to the plants through decomposition. The microorganisms release carbon dioxide gas into the film of water surrounding soil particles, making the water slightly acid. This causes it to react with the rock particles and dissolve them, providing a slow, steady release of nutrients.
All microorganisms decompose decayed vegetation or other microorganisms.
The decayed vegetation, called humus, is the basis for soil life. Without humus, we get no naturally formed nitrogen, and plants become weak and more susceptible to insect attack. Humus has other beneficial effects besides feeding soil microorganisms. It mechanically loosens the soil itself and creates a texture called good tilth. When soil has good tilth, it is soft, porous and easy to work and crumbles easily into fine pieces.