The principal property of the soil fertility is determined by biological factors, mainly by microorganisms. The development of life in soil endows it with the property of fertility. The notion of soil is inseparable from the notion of the development of living organisms in it. Soil is created by microorganisms. Were this life dead or stopped, the former soil would become an object of geology (Vi'lyams, 1950, p 204)
- excerpt from the introduction of Soil Microorganisms and Higher Plants, Krasilnikov N.A.