ABSTRACT
This chapter reviews the state of the art of the general and specific criteria used to determine microbiological activity in soil and to emphasize the exact meaning of each measurement and, therefore, to facilitate its correct use. A plethora of living species inhabit soil and conduct almost all known metabolic reactions. Plant roots and soil fauna and microbiota contribute to the overall soil respiration; therefore, the measurement of soil respiration represents an index of the overall biological activity. Dehydrogenase activity is increased by flooding and by the addition of nutrients to soil. Valid measurements of the activities of enzymes accumulated in soil can be obtained when both the enzyme production and the assimilation of reaction products by growing microorganisms are excluded during the assay period. The interpretation of measurements of enzyme activity in soil is also limited by the difficulty of comparing data obtained by different methods.
