microbial biomass in soil
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b.stev
Microbial Biomass in Soil
What is MICROBIAL BIOMASS?
SOIL BIOTA IS INFLUENCED BY:
HOW the land is used
Management techniques
CHANGE of the practises
this has effect to the microbial process
& their functions of survival in the soil
RESIDUE left after CROPSCROPS are harvested is nutrient
to soil &
facilitates the next crop
growth.
MICROBES
transform chemicals
aid pesticide degradation
participate in soil formation
contribute to soil aggregation
The limits of measurement:
o analytical cost involved
o ambiguous relationship to product
o benchmark values/ interpretation requires time to establish results
o cumbersome/ time needs
DEMAND HAS INCREASED:
can monitor soil quality
an environmental monitor
rapid/ improved techniques
gives the rates of turnover
ANALYSIS for clean food
HOW is this DONE?HOW is this DONE?Extraction of soil is done with a hollow rod to a depth of 10-15 cm
Samples are filtered to remove: stones/ roots/ finer fibres: size 2mm
Storage is at 4oC
SAMPLES are taken in squares at
appropriate spacings to ensure
all land variations are included;
it is quite an extensive process
20g soil are fumigated for a period of 24hrs with CHLOROFORM (CHCl3) in a humid dessicator
THEN: sample is inoculated with 0.5g fresh soil & placed in 1L airtight jars
incubated 10 days at room temperature
Controls - 20.5g samples are put in glass jars at time of fumigation are put to incubation : 10 days
method: chloroform fumigation, incubation
analyses the concentrations: carbon & nitrogen
CO2 produced in the headspace above the incubated samples is determined
by:
GAS CHROMATOGRAPHY
Bc = ( Fc / Kc)
CALCULATION performed from the results:
Kc = 0.41 factor
Bc = biomass of controls
Fc = fumigated samples
DATA is kept in graph/ & numerical value
Field/ SAMPLE sites, mapped for reference
Manufacturer, “HeinemeyerHeinemeyer”- ”- produced an instrumentthat determines microbial biomass by INFRARED ANALYSER
Soil pH - potentiometric 0.01M CaCl2 suspension
H2O content: samples - oven dried 105oC 24hr
CNS-2000 analysis uses dry combustion to measure both the carbon & nitrogen content
SOME OTHER METHODS & analysis to perform
ARE:
Bibliography
Archbold Biological Station. (2008). Soil microbial biomass. Retrieved September 26, 2008, from http://www.archbold-station.org/abs /publicationPDF/Groffman,etal.-2004-Ecosystems.pdf.
Soil Quality Pty Ltd. (2007). Soil quality. Retrieved September 25, 2008, from http://www.soilquality.org.au/factsheets/microbial-biomass
Rothamsted Research. (2004). Method download - soil microbial biomass group - rothamsted. Retrieved September 26, 2008, from http://www.rothamsted. ac.uk/aen/smbweb1/methods.php?id=903
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