Microbial biomass c and ninhydrin-reactive n as Parameters to characterize composting process

The use of compost in agriculture is increasing as a source of organic matter to counteract the decrease of organic matter level in soils and as a means of disposal of agricultural and domestic waste. Despite many researches on the subject, there is still the need to improve our knowledge on the compost process and on the methods to evaluate compost maturity. The composting of organic waste has been defined as a controlled microbial aerobic decomposition process and therefore information on the microbial component of the composting substrates could be expected to give valuable information on the factors influencing the process, on its optimisation and on the quality of the end product.

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.