Carbon and nitrogen recycling from microbial necromass to cope with C:N stoichiometric imbalance by priming

Publication date: Available online 17 January 2020Source: Soil Biology and BiochemistryAuthor(s): Jun Cui, Zhenke Zhu, Xingliang Xu, Shoulong Liu, Davey L. Jones, Yakov Kuzyakov, Olga Shibistova, Jinshui Wu, Tida GeAbstractThe impact of increasing amounts of labile C input on priming effects (PE) on soil organic matter (SOM) mineralization remains unclear, particularly under anoxic conditions and under high C input common in microbial hotspots. PE and their mechanisms were investigated by a 60-day incubation of three flooded paddy soils amended with13C-labeled glucose equivalent to 50–500% of microbial biomass C (MBC). PE (14–55% of unamended soil) peaked at moderate glucose addition rates (i.e., 50–300% of MBC). Glucose addition above 300% of MBC suppressed SOM mineralization but intensified microbial N acquisition, which contradicted the common PE mechanism of accelerating SOM decomposition for N-supply (frequently termed as “N mining”). Particularly at glucose input rate higher than 3 g kg−1 (i.e., 300–500% of MBC), mineral N content dropped on day 2 close to zero (1.1–2.5 mg N kg−1) because of microbial N immobilization. To cope with the N limitation, microorganisms greatly increased N-acetyl glucosaminidase and leucine aminopeptidase activities, while SOM decomposition decreased. Several discrete peaks of glucose-derived CO2 (contributing>80% to total CO2) were observed between days 13–30 under high glucose input (300–500% of MBC), concurren...
Source: Soil Biology and Biochemistry - Category: Biology Source Type: research