In conventional agriculture, soil is looked upon as a base to support the plants and a medium through which nutrients pass into plants through soil solutions. Not much attention is paid to the life in the soil. For organic farming, ‘living’ soil is a prerequisite. Therefore, there is a waiting period or incubation period of three to four years after which the soil becomes fully living, provided the principles of organic farming are applied. Organic manures are applied to the soil so that the soil fauna can feed on them and release the nutrients into the soil solutions, which the plants then absorb in the form of organic ions.

Living soil should be teeming with life. One hectare of land can support more than a million earthworms, millions of other animals such as nematodes, mites, springtails, millipedes, centipedes, wood lice, fly larvae, beetle grubs, wireworms, termites (Fig. 4.1), ants, and so on and an astronomical number of microorganisms. Some spend their whole life in soil; others live in soil at some stage in their life cycle. All of them, however, play an important role in the mobilisation of nutrients in the soil and make a significant contribution to maintaining a healthy soil system and, consequently, healthy plants (Veeresh, 1990 b).

The non-pathogenic microbes nullify the harmful pathogens by competing with them for shelter or as phagocytes.