Microbially-derived nitrogen (N) has been considered as one of important contributors to soil organic N, but few studies have quantified the rate of necromass N decomposition. Here, via an in situ incubation of ¹⁵N-labeled necromass, we found that 33.1–39.5% of the initial ¹⁵N stabilized in the soil as non-living organic N after 803 days of incubation. Bacterial, fungal, and actinobacterial necromass N showed similar decomposition pattern and mean residence time. The decomposition of microbial necromass N was best simulated by a two-pool model where a labile pool decomposed rapidly (0.4 years), and a more recalcitrant pool decomposed at a much slower rate. This finding contrasted with the decomposition of plant litter N, which was better simulated by a single-pool model. The stabilization of necromass N in soils after more than two years suggests the important contribution of microbial residues to soil organic N, which is most likely due to mineral protection from decomposition.

微生物来源的氮（N）被认为是土壤有机氮的重要贡献者之一，但很少有研究量化坏死性氮的分解速率。在这里，通过^15个N标记的坏死瘤的原位培养，我们发现最初^15个N标记的坏死肿瘤的33.1–39.5％孵育803天后，氮作为非生物有机氮稳定在土壤中。细菌，真菌和放线菌性坏死菌N表现出相似的分解模式和平均停留时间。微生物坏死菌N的分解最好通过两池模型进行模拟，其中不稳定的池快速分解（0.4年），而顽固的​​池则以慢得多的速率分解。这一发现与植物凋落物N的分解形成对比，后者可以通过单池模型更好地模拟。两年多后土壤中坏死氮的稳定化表明微生物残留物对土壤有机氮的重要贡献，这很可能是由于矿物保护免受分解所致。