THE NUTRITIONAL REQUIREMENTS OF SOIL BACTERIA???A BASIS FOR DETERMINING THE BACTERIAL EQUILIBRIUM OF SOILS1

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Abstract
A qualitative approach to the problem of the bacterial equilibrium in soil is suggested, based on a determination of the nutritional requirements of bacteria isolated by nonselective plating methods. By using fundamental nutritional differences as a basis for grouping the organisms, according to their growth response in media of varying complexity, a method is proposed for expressing the bacterial equilibrium on a numerical basis. Depending upon the % incidence of bacteria falling into various groups, a value designated as the "bacterial balance index" may be detd. In any given soil an equilibrium exists between bacteria with simple, and those with more complex, growth requirements. This balance may be modified by many factors. Examples are given to show how, by application of the method, changes in the "bacterial balance index" may be observed.