Abstract

Two experiments were carried out on four soils of differing pH, organic C and heavy metal content: in the first the microbial substrate utilization efficiency after growth on glucose was determined, and in the second the microbial maintenance requirement during C limitation. In the first experiment growth characteristics and changes in chloroform-labile total C(C-tot) and ninhydrin-N were determined as well as the fate of the added glucose C(C-glu) over 12 d. In the second experiment the microbial biomass was labelled by additions of C-14-glucose in extremely small amounts so that the biomass was still subject to C limitation. In the first experiment there was an exponential increase in the rate of CO2 production upon glucose addition, indicating exponential microbial growth. Microbial growth characteristics derived from the respiration curves showed differences between soils. but no consistent response to low pH or heavy metal stress. The C-glu data did not give a valid estimate of the substrate utilization efficiency, but indicated a lower extractability of the glucose-derived biomass C in the (NH4)(2)SO4- and the sewage sludge-amended soils than in the Ca(NO3)(2)-fertilized and FYM-amended soils. Changes in biomass C and N were contradictory so that we could not conclude whether or not microorganisms subjected to stress were characterized by a lower substrate utilization efficiency. The C-tot specific respiration rate during conditions of C-limitation in the second experiment was higher in the (NH4)(2)SO4-fertilized and in the sewage sludge-amended soil compared to that in the Ca(NO3)(2)-fertilized and FYM-amended soils, indicating a higher maintenance requirement in the former soils. Respiration of C-glu reflected differences in the specific respiration rate. Loss of microbially-incorporated C-glu was larger in the (NH4)(2)SO4- and the sewage sludge-amended soils. The results indicate that higher maintenance requirements may contribute to the lower biomass C-to-soil organic C ratio that characterized the acid-and the heavy metal-contaminated soil. (C) 1998 Elsevier Science Ltd. All rights reserved.

Published in

Soil Biology and Biochemistry
1998, Volume: 30, number: 5, pages: 633-641
Publisher: PERGAMON-ELSEVIER SCIENCE LTD

SLU Authors

• Dahlin, Sigrun

  • Department of Soil Sciences, Swedish University of Agricultural Sciences
    

• Witter, Ernst

  • Department of Soil Sciences, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Soil Science


Publication identifier

DOI: https://doi.org/10.1016/S0038-0717(97)00156-9

Permanent link to this page (URI)

https://res.slu.se/id/publ/66506