Irrigation of Suaeda salsa with Saline Wastewater and Microalgae: Improving Saline–Alkali Soil and Revealing the Composition and Function of Rhizosphere Bacteria

Limited research has been conducted on the potential and mechanisms of irrigating <i>Suaeda salsa</i> with wastewater and microalgae to improve saline-alkali land. This study used three irrigation treatments (freshwater, saline wastewater, and saline wastewater with microalgae) to irrigate <i>S. salsa</i>, and microalgae promoted the growth of <i>S. salsa</i> and increased soil nutrient content, increasing available nitrogen (4.85%), available phosphorus (44.51%), and organic carbon (24.05%) while alleviating salt stress through reduced soil salinity (13.52%) and electrical conductivity (21.62%). These changes promoted eutrophic bacteria while inhibiting oligotrophic bacteria. Bacterial community composition exhibited significant variations, primarily driven by soil pH, total nitrogen, and organic carbon content. Notably, rhizosphere bacteria showed enhanced functional capabilities, with increased abundance of salt stress resistance and nitrogen metabolism-related genes compared to original soil, particularly under saline irrigation conditions. Furthermore, microalgae addition enriched nitrogen metabolism-related gene abundance. These findings revealed the potential role of key bacteria in enhancing plant growth and the soil environment and highlighted the potential of applying <i>S. salsa</i>, wastewater, and microalgae for the synergistic improvement of saline-alkali land.