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