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Modified Calibration Procedure for the Measurement of Microbial Sulfur in Soil
Author(s) -
Castellano S. D.,
Dick R. P.
Publication year - 1991
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1991.03615995005500010049x
Subject(s) - loam , serial dilution , microorganism , soil water , biomass (ecology) , chemistry , bacteria , fumigation , environmental chemistry , silt , dilution , environmental science , mineralogy , botany , agronomy , soil science , biology , medicine , paleontology , genetics , alternative medicine , physics , pathology , thermodynamics
To better estimate S biomass in soils, an alternative calibration technique for the measurement of microbial biomass S in soil was developed. Rather than using pure cultures of bacteria and fungi to determine the biomass‐S calibration constant ( K s ), cultures of bacteria and fungi were grown using soil dilutions as primary inoculum. These microorganisms were harvested and washed, and dense suspensions of bacteria or fungi (in 0.15 M NaCl matrix solution) were prepared. The suspensions were used as inoculum for the calibration procedure, where bacteria or fungi were each grown at three S concentrations (1, 4, or 16 mg SO 4 ‐S L −1 ) and subsequently added to soil and fumigated with CHCl 3 . The mean value of 39.3% was calculated for the proportion of microbial S extracted with calcium phosphate [8 m M Ca(H 2 PO 4 ) 2 ] from a Woodburn silt loam (a fine‐silty, mixed, mesic Aquultic Argixeroll) following CHCl 3 fumigation. This procedure may better reflect the soil microbial biomass than using pure cultures, because soils have mixed microbial populations.