Hi
I'm searching for a simple method to assess microbial biomass C in soils (for contaminated soils by heavy metals and uncontaminated forest soils).
We don't have a significant number of experimental equipment, such as a TOC analyser, although we have microplate reader used for enzymatic assays....
Also, are there any book or paper with a review of used methods? I saw Marteens (1995) https://link.springer.com/article/10.1007/BF00336142 but it's a bit old.)
Regards and thank you in advance.
Soil microbial biomass carbon (SMB-C) was determined by Fumigation-extraction method as per the procedure given by Vance et al. (1987). Twenty g soil (air dried) was fumigated with 50 ml of ethanol free chloroform in a desiccator. Ethanol free chloroform was prepared by passing 100 ml chloroform through a glass column containing 75 g basic aluminium oxide (Vogel, 1978). After 24 hours fumigation at 25oC, chloroform was removed by repeated evacuations. The fumigated soil samples were extracted with 80 ml of 0.5 M K2S04 for 30 minutes on a rotary shaker at 160 rpm and filtered. 8ml of filtrate was refluxed with 2ml of K2Cr2O7 and 15 ml of diacid mixture (H2SO4: H3PO4 : : 2:1) for half hour on hot plate at 150oC with three drops of phenanthroline indicator solution. After cooling, the mixture was titrated with Ferrous Ammonium Solution. Similar procedure was followed for non-fumigated soil samples except that these samples were not fumigated.
Soil microbial biomass C was calculated as under: SMB-C (mg kg-1 ) = 2.64 (Extractable C in fumigated soil- Extractable C in non- xlix fumigated soil)
Where: 2.64 = Kc Factor (Vance et al., 1987)
You can also read the paper of Gregorich et al. (1990) Soil Biology and Biochemistry 22: 1009-1011. The other papers are already listed by Arvind Singh and Rahangdale.
The fumigation followed by extraction and analysis are by far the simplest method available, thus far.
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