Saline-alkali farmlands in the Ningxia-Inner Mongolia Irrigation District suffer from substantial nitrogen loss and low nitrogen fertilizer use efficiency. Developing high-efficiency and eco-friendly alternative fertilizers is crucial for advancing sustainable agriculture and ecological protection in saline-alkali regions. In this study, saline-alkali farmland soil from the Ningxia Irrigation District was used as the research substrate. Organic fertilizer co-prepared with biochar, wood vinegar, chicken manure, and straw via fermentation (BCOF) was applied as a partial substitute for inorganic fertilizer at addition rates of 1% and 2%. Organic fertilizer derived from chicken manure-straw compost (OF) served as the control. A pot experiment with maize was conducted to investigate the effects of BCOF on ammonia volatilization and maize growth in saline-alkali soil, as well as the underlying mechanisms. Results showed that compared to the no-fertilizer control (CK0), BCOF treatments reduced the peak concentration of soil ammonium nitrogen by over 30% and cumulative ammonia volatilization by 23.72%–33.90%. Additionally, BCOF effectively regulated saline-alkali salt distribution and soil ionic composition, mitigating the accumulation of salt ions such as Na₊ ^{and Cl?}. Notably, the nitrogen content in maize straw under the 1% BCOF treatment increased significantly by 45.01%. Analysis of bacterial community structure revealed that both OF and BCOF increased the abundance of Firmicutes and Chloroflexi. Specifically, the 2% BCOF treatment fostered a bacterial community with high connectivity and modularity, enriched key module species represented by Bacillus, and enhanced the stability and resilience of the bacterial community. Redundancy analysis and correlation analysis demonstrated that the reduction in ammonia volatilization and improvements in maize nutrient content under BCOF treatments were significantly correlated with key bacterial taxa. In conclusion, organic fertilizer prepared with biochar and wood vinegar can effectively reduce ammonia volatilization from saline-alkali soil in the Ningxia-Inner Mongolia Irrigation District and promote crop growth by enhancing nitrogen adsorption-fixation and reshaping bacterial community networks, providing a feasible technical approach for sustainable agriculture in saline-alkali regions.