Standard operating procedure for soil microbial biomass (carbon): chloroform fumigation-extraction method

Abstract

Microbial biomass is considered as an estimation of soil biological activities and the capacity to mediate soil biochemical reactions. It is the most dynamic and labile of soil organic matter fractions, generally accounting for 1 to 5 percent of soil organic matter and very sensitive to soil management. The need to quantify soil microbiota has become increasingly relevant in current times as they are responsible for many different processes like the degradation of organic matter, the stability of aggregates and most of the nutrient cycling that occurs in soils. This standard operating procedure (SOP) focuses on the determination of soil microbial biomass using the chloroform fumigation-extraction method, which is applicable to both aerobic and anaerobic conditions over the whole range of soil pH, regardless of land use type. While chloroform fumigation also affects soil fauna, the carbon aliquot derived from these organisms is generally small (less than 5 percent) and can usually be disregarded.