Chloroform fumigation extraction for measuring soil microbial biomass: The validity of using samples approaching water saturation

Geoderma ◽  
2018 ◽  
Vol 319 ◽  
pp. 204-207 ◽  
Author(s):  
Adi Oren ◽  
Nativ Rotbart ◽  
Mikhail Borisover ◽  
Asher Bar-Tal
Keyword(s):  
Microbial Biomass ◽  
Soil Microbial Biomass ◽  
Water Saturation ◽  
Soil Microbial ◽  
Chloroform Fumigation ◽  
Fumigation Extraction

scholarly journals Defining a realistic control for the chloroform fumigation-incubation method using microscopic counting and 14C-substrates

1996 ◽  
Vol 76 (4) ◽  
pp. 459-467 ◽  
Author(s):  
William R. Horwath ◽  
Eldor A. Paul ◽  
David Harris ◽  
Jeannette Norton ◽  
Leslie Jagger ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Soil Microbial Biomass ◽  
Microbial Biomass Carbon ◽  
Soil Depth ◽  
Temporal Trends ◽  
Biomass Carbon ◽  
Soil Microbial ◽  
Microbial C ◽  
Parameter Values ◽  
Chloroform Fumigation

Chloroform fumigation-incubation (CFI) has made possible the extensive characterization of soil microbial biomass carbon (C) (MBC). Defining the non-microbial C mineralized in soils following fumigation remains the major limitation of CFI. The mineralization of non-microbial C during CFI was examined by adding 14C-maize to soil before incubation. The decomposition of the 14C-maize during a 10-d incubation after fumigation was 22.5% that in non-fumigated control soils. Re-inoculation of the fumigated soil raised 14C-maize decomposition to 77% that of the unfumigated control. A method was developed which varies the proportion of mineralized C from the unfumigated soil (UFC) that is subtracted in calculating CFI biomasss C. The proportion subtracted (P) varies according to a linear function of the ratio of C mineralized in the fumigated (FC) and unfumigated samples (FC/UFC) with two parameters K1 and K2 (P = K1FC/UFC) + K2). These parameters were estimated by regression of CFI biomass C, calculated according to the equation MBC = (FC − PUFC)/0.41, against that derived by direct microscopy in a series of California soils. Parameter values which gave the best estimate of microscopic biomass from the fumigation data were K1 = 0.29 and K2 = 0.23 (R2 = 0.87). Substituting these parameter values, the equation can be simplified to MBC = 1.73FC − 0.56UFC. The equation was applied to other CFI data to determine its effect on the measurement of MBC. The use of this approach corrected data that were previously difficult to interpret and helped to reveal temporal trends and changes in MBC associated with soil depth. Key words: Chloroform fumigation-incubation, soil microbial biomass, microscopically estimated biomass, carbon, control, 14C

Soil C extracted with water or K2SO4: pH effect on determination of microbial biomass

1999 ◽  
Vol 79 (4) ◽  
pp. 529-533 ◽  
Author(s):  
R. L. Haney ◽  
A. J. Franzluebbers ◽  
F. M. Hons ◽  
D. A. Zuberer
Keyword(s):  
Microbial Biomass ◽  
Ph Effect ◽  
Calcareous Soils ◽  
Microbial Biomass C ◽  
Soil C ◽  
Soil Microbial ◽  
The Past ◽  
Chloroform Fumigation ◽  
Fumigation Extraction

Routine determination of soil microbial biomass C has shifted during the past decade from chloroform fumigation-incubation to chloroform fumigation-extraction using 0.5 M K2SO4 as extractant. We compared extractable C with water and 0.5 M K2SO4 in eight soils ranging in pH from 5.4 to 8.3. In unfumigated soils with low pH, extractable C was 0.8- to 1.2-fold greater with water than with 0.5 M K2SO4. However, in unfumigated soils with pH > 7.7, extractable C, although not statistically significant, was 11 to 19% less with water than with 0.5 M K2SO4. In fumigated soils, no difference in extractable C between water and 0.5 M K2SO4 was detected among soils with pH < 7.7, but extractable C was 13 to 17% less with water than with 0.5 M K2SO4 with pH > 7.7. Our results suggest that 0.5 M K2SO4 (1) may flocculate soil and cause adsorption of solubilized C onto colloids at pH < 7.7, but (2) may disperse calcareous soils at pH > 7.7, thereby differentially affecting the fate of solubilized C depending upon soil pH. Our results put into question the widespread adaptability of using chloroform fumigation-extraction to estimate microbial biomass C. Key words: Extractable carbon, chloroform fumigation-extraction, microbial biomass

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