为探讨不同施氮处理下田菁翻压还田对滩涂盐渍土的改良效果，通过田间小区试验研究了不同施氮水平下（CK、SN1、SN2、SN3、SN4对应的施氮量分别为0、90、135、180、225 kg/hm²）绿肥田菁还田对土壤碳氮、pH、水溶性盐和细菌群落结构的影响。结果表明：SN3处理下田菁生物量和碳、氮累积量最高，分别为41 882、3 756和101.5 kg/hm²。作绿肥翻压还田后，则以SN2处理土壤有机碳、全氮含量最高，分别为6.51 g/kg和0.637 g/kg。各施氮处理下，田菁翻压后土壤微生物生物量碳氮含量低于CK处理。随田菁翻压量的增加，土壤pH呈逐步下降趋势，而土壤水溶性盐总量则随施氮水平和翻压量的增加而上升，但较种植前明显降低。不同施氮处理田菁翻压后，土壤中具有一定有机降解功能的变形菌门、酸杆菌门、拟杆菌门、放线菌门和绿弯菌门等细菌类群占据主导地位，且相对丰度随田菁翻压量的增加呈一定变化趋势，但细菌群落结构变化不明显。土壤门水平优势菌群相对丰度与土壤碳氮含量、pH和水溶性盐总量等指标均呈一定的相关关系，其中以拟杆菌门、厚壁菌门、蓝菌门、绿弯菌门和迷踪菌门相对丰度与土壤有机碳和全氮含量的相关性较显著。综上所述，SN2处理下田菁翻压还田可显著提升滩涂土壤有机碳和全氮含量；不同施氮水平下生长的田菁翻压还田后，土壤水溶性盐总量均较种植前显著降低，主要优势菌群均有利于绿肥降解与土壤培肥，改善滩涂土壤微生态环境。

In order to explore the improvement effects of Sesbania cannabina returning on saline soils in tidal flat under different nitrogen application treatments, a field plot experiment was conducted to study the effects of returning green manure Sesbania cannabina to the field on the contents of soil carbon, nitrogen, pH and total water-soluble salt and bacterial community structures under different nitrogen application treatments (CK, SN1, SN2, SN3, SN4 corresponding to nitrogen application rates of 0, 90, 135, 180, and 225 kg/hm², respectively). The results showed that the biomass, carbon and nitrogen accumulation of Sesbania cannabina were the highest under SN3 which were 41 882, 3 756and 101.5 kg/hm², respectively. After returning green manure to the field, soil organic carbon and total nitrogen contents of SN2 were the highest, which were 6.51 g/kg and 0.637 g/kg, respectively. Soil microbial biomass carbon and nitrogen were lower than CK after nitrogen application. With the increase of the amount of Sesbania cannabina overturning, soil pH decreased gradually, while soil total water-soluble salt increased with the increase of nitrogen application level or the amount of Sesbania cannabina overturning, but it was significantly lower than that before planting. After the overturning of Sesbania cannabina under different nitrogen application treatments, Proteobacteria, Acidobacteria, Bacteroidetes, Actinobacteria and Chloroflexi, which have certain organic degradation function were the dominant phyla in the soil. The relative abundance showed a certain change trend with the increase of the turnover amount of Sesbania cannabina, but the change of bacterial community structure was not obvious. There was a certain correlation between the dominant bacteria at phylum level with soil carbon, nitrogen, pH and total water-soluble salt. Among them, the correlation of Bacteroidetes, Firmicutes, Cyanobacteria, Chloroflexi and Mitrobacter with soil organic carbon and total nitrogen were significant. In summary, the returning of Sesbania cannabina to the field under SN2 can significantly increase the contents of soil organic carbon and total nitrogen in the tidal flat, the returning of Sesbania cannabina can significantly reduce soil water-soluble salt, and the main dominant soil bacterium groups are beneficial to green manure degradation and soil fertilization, thus can improve soil micro-ecological environment of coastal area.

S147.2；S158.3

江苏省碳达峰碳中和科技创新专项（BE2022304），国家绿肥产业技术体系项目（CARS-22-G-15）和江苏省沿海开发集团揭榜挂帅项目（2022YHTDJB014）资助。