microbial biomass in soil

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Microbial biomass in soil, measurement by chloroform fumigation incubation method, limits of measurement of microbial biomass, why microbes are important in the soil, why microbial biomass is important in the 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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