The soil microbial biomass acts as the transformation agent of the organic matter in soil. The biomass is both a source and sink of the nutrients C, N, P and S held in the organic matter. It is the center of the majority of biological activity in soil. It is obvious that management practices substantially affect the microbial biomass of soils. For example, organic amended soils are supposed to have higher and more diverse soil microbial biomass than conventionally managed or intensively cropped soils. So what is the best and efficient method of measuring soil microbial biomass and diversity? How are the relationships between microbial biomass and the elements C, N, P and S?
Please follow this link.
http://link.springer.com/chapter/10.1007/978-94-010-0131-1_3#page-1
Good luck
Please have a look at these links also.
https://www.researchgate.net/publication/277131720_Microbial_Biomass_Measurement_Methods
https://www.researchgate.net/publication/225400838_Relationship_between_soil_microbial_biomass_determined_by_SIR_and_PLFA_analysis_in_floodplain_soils
https://www.researchgate.net/publication/223858417_A_Physiological_Method_for_the_Quantitative_Measurement_of_Microbial_Biomass_in_Soil
Chapter Microbial Biomass Measurement Methods.
Article Relationship between soil microbial biomass determined by SI...
Article A Physiological Method for the Quantitative Measurement of M...
Thus microbes can be considered as slow release fertilisers that store nutrients (mainly N and P) when nutrient concentrations are high and then release them
For total microbial biomass-C, you can use soil fumigation: http://www.sciencedirect.com/science/article/pii/0038071790900463
It's a relatively affordable method, which requires a desiccator and a carbon analyzer.
This method measures soil carbon before and after fumigation. Since fumigation lyses cells, the difference in carbon measured is biomass-C. This gives you the biomass total in the soil, but doesn't answer the diversity question.
Thank you Hala. Yes, Fmigation-Extraction is the first automated procedure for measuring soil microbial biomass carbon. But the conversion of measured data into microbial biomass values is very important. Is there a conversion factor that may translate the total soil organic carbon to soil microbial biomass?
Its a point of discussion, what should be the conversion factor for soil microbial biomass from SMBC.
Thats a very good point Getachew , the conversion factor to convert soil organic carbon into soil microbial biomass carbon ..?
Yes, Anoop, it will be informative if anyone familiar with different methods of soil microbial biomass determination comments on. I think if a conversion factor is developed it will be simple to estimate the soil microbial biomass.
Dr.Agegnehu,good discussion on an important parameter.I never estimated this parameter but seen practically when my colleagues were struggling to get reproducible results, more than two decades back.I feel it is not desired to compute microbial biomass from total carbon even if some body gives a conversion factor.The point raised by Dr.Naik ,the conversion factor for computing microbial biomass from SMBC is really important.One should not borrow it from others from very contrasting soils,climates etc.Dr.Malhotra's comment of describing soil micribial biomass nutrients as slow release fertilizer is interesting,as they take up nutrients at good times(when nutrients are abundent or adequate ) and release them to plant uptake when nutrient supply is limited in soil(because of nutrient transformations/fixation and exhaustion of readily decomposable organic matte in soil).
Regarding total microbial biomass-C, there is no conversion factor: you use fumigation (http://www.sciencedirect.com/science/article/pii/0038071790900463), and subtract C/unit soil obtain in post fumigation samples, from pre-fumigation samples. This results in biomass-C (The C obtained from the lysed biomass).
PS: When I first posted this reply, I accidentally left out the main piece of information and posted a repeat of a previous answer.
The fumigation-extraction-based techniques are a fairly efficient way of getting microbial biomass C, N or P. Microbial diversity is a very quickly moving field, with the next-generation molecular biology techniques providing huge amounts of information.
Working out Shannon index gives fair idea about diversity....
The fumigation-extraction-based techniques are good method of microbial biomass
there is chloroform fumigation incubation ( DFI) to measure MBC from the microbial respiration methods ( alkaline titration method) .
basically, you first must figure out the CO2 release without fumigation , secondly you must also find the CO2 after the soil being fumigated and incubated for 10 days in flasks.
once you got all detials then an equation will be ready to subtract the fumigated CO2 from non-fumigated CO2 with using some conversion factors.
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