Soil, like air and water, is a fundamental natural resource supporting a variety of ecosystem goods and services to the benefit of the mankind. While production function of soil was recognized long back, importance of conservation and enhancement of ecosystem services rendered by soil (e.g., carbon sequestration, water purification, recharge of ground water, control of populations of pathogens, biological nitrogen fixation and biodiversity conservation) has been realized only in the recent past. A concern for maintaing/improving soil quality arose long after that for water and soil. Soil processes are such that soil has been considered as an ecosystem by itself rather than a component of ecosystem. While criteria, indicators and standards of water and air quality are unambiguous and universally accepted, the concept of soil quality, further elaborated as soil health is still evolving, with soil quality legislations framed so far only in a few countries Soil quality can be defined as the fitness of a specific kind of soil, to function within its capacity and within natural or managed ecosystem boundaries, to sustain plant and animal productivity,maintain or enhance water and air quality, and support human health and habitation (Karlen et al. 1997, Arshad and Martin 2002). Consideration of soil as a finite and living resource, led to the concept of soil health defined as the continued capacity of soil to function as a vital living system, within ecosystem and land-use boundaries, to sustain biological productivity, maintain or enhance the quality of air and water, and promote plant, animal and human health (Doran et al. 1996, 1998, Doran and Zeiss 2000). Though the use of soil health has emerged in recent years, variation in ability of soils to suppress plant diseases is known since many decades (Janvier et al. 2007).

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