SOIL RESPIRATION PROFILES AND PROTOZOAN ENUMERATION AGREE AS MICROBIAL-GROWTH INDICATORS

Carbon, nitrogen or phosphorus limitation of microbial growth in a for est and a field soil was evaluated from measurements of respiration an d protozoan counts after nutrient addition. In both soils simultaneous addition of C (glucose) and N (NH4NO3) resulted in microbial growth a s indicated by a gradual increase in respiration rate whereas a single addition of C did not induce microbial growth. Addition of P (KH2PO4 + Na2HPO4) to C-amended soil stimulated activity slightly in forest so il but not in field soil whereas addition of P to soil amended with C and N increased growth markedly in both soils. The stimulation of micr obial growth indicated by respiration profiles following C and N addit ion was supported by enumeration of bacterivorous protozoa. The number s of soil protozoa increased above the control only when C and N were added simultaneously. These observations lend support to the proposal that respiration patterns may be valuable in an analysis of nutrient l imitation of microbial growth in soils. Copyright (C) 1996 Elsevier Sc ience Ltd.