Microbial Biomass generally constitute . . . . . . . . % of total soil mass.

Soil microbial biomass is a measure of the mass of the living component of soil organic matter. The microbial biomass decomposes plant and animal residues and soil organic matter to release carbon dioxide and plant available nutrients.
The microbial biomass of the soil was determined by killing and lysing the soil microbes by fumigation with chloroform, irradiation with gamma rays or irradiation with microwaves.
Microbial biomass generally constitutes 0.01 - 0.4% of total soil mass.