The incorporation of green manure into cropping systems is a potential strategy for sequestering soil carbon (C), especially in saline-alkali soil. Yet, there are still unknown about the substitution impacts of green manure on nitrogen (N) fertilizer in wheat-green manure multiple cropping system. Herein, a five-year field experiment was performed to determine the impact of three levels of N fertilizer inputs [i.e., N fertilizer reduced by 0 % (100N), 10 % (90 N), and 20 % (80 N)] with aboveground biomass of green manure removal (0GM) and return (100GM) on soil organic carbon (SOC) storage and its primary determinants. The results demonstrated that no significant interaction on SOC storage was detected between green manure and N fertilizer management. 80 N enhanced SOC storage in bulk soil by 7.4 and 13.2 % in 0–20 cm soil depth relative to 100 N and 90 N ( < 0.05). Regardless of N fertilizer levels, compared with 100GM, 0GM increased SOC storage in bulk soil by 14.2–34.6 % in 0–40 cm soil depth ( < 0.05). This was explained by an increase in soil macro-aggregates (>2 and 0.25–2 mm) proportion contributing to SOC physical protection. Meanwhile, the improvement of SOC storage under 0GM was due to the decrease of soil C- and N-acquisition enzyme activities, and microbial resource limitation. Alternatively, the variation partitioning analyses (VPA) results further suggested that C- and N-acquisition enzyme activities, as well as microbial resource limitation were the most important factors for SOC storage. The findings highlighted those biological factors played a dominant role in SOC accumulation compared to physical factors. The aboveground biomass of green manure removal with N fertilizer reduced by 20 % is a viable option to enhance SOC storage in a wheat-green manure multiple cropping system.

中文翻译：

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减氮绿肥去除提高了小麦-绿肥种植系统中盐碱地的有机碳储量

将绿肥纳入耕作系统是固存土壤碳（C）的潜在策略，特别是在盐碱土壤中。然而，绿肥对小麦-绿肥复种制度中氮肥的替代影响尚不清楚。在此，进行了为期五年的田间试验，以确定三种氮肥投入水平的影响[即氮肥减少0％（100N）、10％（90N）和20％（80N）]绿肥去除（0GM）和返回（100GM）的地上生物量对土壤有机碳（SOC）储存的影响及其主要决定因素。结果表明，绿肥和氮肥管理之间没有检测到对 SOC 存储的显着交互作用。相对于 100 N 和 90 N (< 0.05)，80 N 使 0-20 cm 土壤深度的土壤中 SOC 储存量提高 7.4% 和 13.2%。无论氮肥水平如何，与 100GM 相比，0GM 在 0-40 cm 土层深度（ < 0.05）使大块土壤的 SOC 存储量增加了 14.2-34.6%。这是因为有助于 SOC 物理保护的土壤大团聚体（>2 和 0.25-2 毫米）比例的增加。同时，0GM下SOC储存的改善是由于土壤C和N获取酶活性的降低以及微生物资源的限制。另外，变异分配分析（VPA）结果进一步表明，碳和氮获取酶活性以及微生物资源限制是 SOC 储存的最重要因素。研究结果强调，与物理因素相比，生物因素在 SOC 积累中起着主导作用。氮肥去除绿肥的地上生物量减少 20%，是提高小麦-绿肥复种系统中 SOC 储存的可行选择。