Effects of microbial organic fertilizer on nitrogen cycling-related microbial communities and nitrogen-fixing system stability in saline soil

Microbial organic fertilizers (MOFs) have shown to improve nitrogen fixation efficiency, particularly under saline or nutrient-stressed conditions. However, the mechanisms by which MOF influence nitrogen-cycling microorganisms and ammonia (NH₃) volatilization in saline-alkali soils are still unclear. This 2-year field study demonstrated that the application of MOF reduced NH₃ emissions by 21% and 10%, compared to farmyard manure fertilizer (FMF) and control (CK) treatments. MOF treatment significantly enhanced crop nitrogen uptake by 40.5% and 80.3%, respectively, relative to FMF and CK. The number of nifH gene copies was significantly higher with MOF treatment than with CK treatment, with an increase of up to 98%. The abundance of nifH increased by 41.3% and 25.3% under the MOF treatment compared to under the control and FMF treatments. These results suggest that MOF use could be a feasible approach to enhancing crop nitrogen uptake by establishing a complex, stable, and collaborative nitrogen-fixing system.