Microbial residues are essential for soil organic carbon (SOC) accumulation and stability. However, the interactive effects of cropping system and fertilisation on microbial residues and their contributions to SOC have not been addressed. Herein, we used amino sugars as tracers for microbial residues and analysed the dynamics of microbial residues in a 31-year-long experiment in a highland agroecosystem to understand how effects of fertilisation vary with cropping systems. The cropping systems included continuous alfalfa (AC, a pure legume system), continuous winter wheat (WC, a non-legume system) and grain-legume rotation (GLR) system. The fertilization treatments were the unfertilised control (CK), phosphorus (P), P and nitrogen (NP) and NP and manure (NPM). When averaged across the experimental periods, compared with the GLR and WC systems, the AC system increased microbial residues, the ratio of fungal-to-bacterial residues and the contribution of fungal residues to SOC. The NP and NPM increased microbial residues, and the effects of NPM were greater than those of NP. However, the contribution of microbial residues to SOC was lower in the NPM treatment than that in the NP treatment. The effects of NP or NPM on microbial residues were similar among cropping systems, while the effect of P was greater in the AC system but smaller in the WC system in comparison with those in the GLR system. Therefore, the pure legume cropping system was conducive to SOC accumulation mainly by increasing fungal residues in soils. Manure combined with chemical fertilisers was more beneficial to the accumulation of microbial residues, but SOC accumulation caused by it was less attributable to the increase in microbial-derived C. Moreover, P fertiliser was crucial for the accumulation of microbial residues in legume-included cropping systems.

中文翻译：

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一项长达 31 年的实验中受种植系统和施肥影响的高原农业生态系统中微生物残留的动态

微生物残留物对于土壤有机碳 (SOC) 积累和稳定性至关重要。然而，耕作制度和施肥对微生物残留的相互作用及其对 SOC 的贡献尚未得到解决。在这里，我们使用氨基糖作为微生物残留的示踪剂，并在高原农业生态系统中进行了 31 年的实验，分析了微生物残留的动态，以了解施肥的影响如何随种植系统而变化。种植系统包括连续苜蓿（AC，纯豆科植物系统）、连续冬小麦（WC，非豆科植物系统）和谷物-豆类轮作（GLR）系统。施肥处理是未施肥的对照（CK）、磷（P）、磷和氮（NP）以及NP和粪肥（NPM）。当在实验期间平均时，与 GLR 和 WC 系统相比，AC 系统增加了微生物残留、真菌与细菌残留的比率以及真菌残留对 SOC 的贡献。NP和NPM增加了微生物残留，NPM的影响大于NP。然而，NPM 处理中微生物残留对 SOC 的贡献低于 NP 处理。与 GLR 系统相比，NP 或 NPM 对微生物残留的影响在种植系统中相似，而 P 在 AC 系统中的影响更大，但在 WC 系统中的影响较小。因此，纯豆类种植制度主要通过增加土壤中的真菌残留量来促进 SOC 积累。粪肥配施化肥更有利于微生物残留物的积累，