The SOIL QUALITY and its BIOLOGICAL ACTIVITY are closely linked. Many millions of microorganisms are involved in the complex cycles of the rhizosphere, directly affecting soil fertility, the availability of nutrients, the resistance of plants to stress, etc. There is a great interdependence between the different classes of microorganisms, for example: epigean fauna, hypogean fauna and earthworms, which ensure the connection between the two previous categories. In this way the earthworms favor the movement and integration of organic substance and nutrients between the different layers of the soil, increasing their fertility. Furthermore the tunnels improve the circulation of water and oxygen in the soil, to the advantage of the roots. To check if the soil is biologically active, it is necessary to evaluate the presence of earthworms (presence on the soil surface of the typical pyramidal heaps of earth)! There is no doubt that maintaining a good biological soil activity is essential for achieving high quality agricultural production.