The soil microbial biomass concept proposed by Jenkinson (Powlson, 1994) considers the entire soil microbial population as a single entity. The main technique developed to measure the size of the whole soil microbial population is the fumigation-extraction (FE) technique. Some authors have used the fumigation-extraction technique with compost substrates (De Nobili et al., 1996; Hellmann et al., 1997; Horwath and Elliot, 1996; Mondini et al., 1997). Results suggested that application of the microbial biomass concept to compost could give valuable information on the process. Nevertheless compost substrates are quite different from soil, and application of microbial biomass technique must be carefully checked throughout.
The aim of this work was to study microbial biomass C and ninhydrin reactive N dynamics during composting.