Dear Ayad,

Various indirect methods have been recommended for estimating soil C which can be readily implemented in a limited resource environment but they require more evaluation in terms of accuracy. Study  results showed that both dichromate oxidation and loss-on-ignition had substantial limitations when used to analyze the low carbon soils within the region. Diffused reflectance spectroscopy using either the near- or midinfrared spectral regions performed well for predicting soil organic carbon as well as sand, silt and clay content. These results indicate that once calibrated, infrared spectroscopy holds great promise for quantifying soil properties.

Methods of Measuring Microbial Biomass Pool Sizes. Microbial biomass has been measured in soil by a variety of methods. The ideal method would be rapid, sensitive, and distinguish living and active microbial cells from the microbial biomass that is essentially dormant or unresponsive to the addition of a readily available C source to the soil system. The classical procedure for the estimation of microbial biomass is by direct microscopy. Biovolume of microbial cells in a

microscopic field is determined and the biovolume is then converted to biomass.

A second procedure is to extract a specific component of the microbial biomass and use the concentration of this component to estimate the concentration of the total biomass. Probably the most commonly used classical technique for determining the microbial biomass size is that of chloroform fumigation. Fumigation ruptures microbial cells and releases cell walls and cellular contents into the soil. If incubation follows the fumigation, a "flush of decomposition" of the soil organic matter occurs that is due to the decomposition of microorganisms killed during fumigation. When the fumigation and subsequent incubation procedures are conducted under a strict set of conditions, the size of the biomass pool of C can

be determined by the size of the carbon dioxide flush.

For more information on the methods described above, please see publications contained in the attached two files.

Hoping this will be helpful,

Rafik

Dear Rafik,

Thanks a lot, I'm so appreciate your response, if I have total count of Bacteria and Fungi in Soil, are there any relationships between Total count and Biomass.

Best Regards

Sincerely

Ayad

Dear Ayad,

For sure. There is a relationship between the microorganism count and biomass:

The classical procedure for the estimation of microbial biomass is by direct microscopy. Biovolume of microbial cells in a microscopic field is determined and the biovolume is then converted to biomass. For conversion of biovolume data to biomass C values, it is necessary to know cell density, cell matter content, and the C content of the dry matter. A conversion factor of 0.13 has been determined assuming the wet density of soil microorganisms is 1.1 g cm-3, a dry matter content of 0.28 g g-1, and a C content of microbial cells of 0.47 g g-1. Using these assumptions you can obtain

(1.1 g cm-3)(0.25 g g-1) 0.47 g g-1) = 0. 13 g cm-3

and

biovolume (in cm3 g-1) x 0.13 g cm-3 = biomass C (g g-1).

A second procedure is to extract a specific component of the microbial biomass and use the concentration of this component to estimate the concentration of the total biomass. For a specific biomass component to accurately reflect the quantity of the microbial biomass in soil it must meet the following requirements.

1. It must be present in all of the biomass at a known concentration.

2. It must be present in living organisms only and must not accumulate in the soil in

nonliving material.

3. It must be extracted quantitatively from soil.

4. It must have a reliable and accurate method of analysis once it is extracted.

For more, please see attached file with the name "Organic Carbon 2".

Hoping this will be helpful,

Rafik

[email protected]