Remineralization of nitrogen immobilized by soil microorganisms and effect of drying and rewetting of soils

Microbial biomass is considered to act as one of the major sources of inorganic N pool in soil. Many investigators indicated that significant portions of the flux of inorganic N in soil originated from the mineralization of dead microbial biomass (Ladd et al. 1977; Powlson 1980; Marumoto et al. 1982a, b). However, their findings were based in experiments in which the nitrogen flux from the microbial biomass increased by the addition of dead microbial biomass and/or by the pre-treatment of soils under artificial conditions such as oven-drying, grinding, fumigation. Thus, to determine the nitrogen flux from the microbial biomass in natural soil ecosystems and to analyze the quantitative role of microbial biomass in the nitrogen cycle, it is necessary to determine the flux of inorganic N from microbial biomass under natural field conditions.