Copyrolysis of Biomass with Ca3(PO4)2 and MgO for Loading Enterobacter hormaechei Wu15 to Promote Pea Growth in Saline–Alkali Soil

Biochar-based bacteria have a significant promoting effect on plant growth, but their effectiveness in improving saline–alkali soils still needs to be improved. In order to fill in these aspects, a modified biochar was obtained by copyrolysis of Ca3(PO4)2, MgO, and biomass and cocultured with Enterobacter hormaechei Wu15. The surface of biochar became rough after the addition of Ca3(PO4)2 and MgO, and the Brunauer–Emmett–Teller surface area increased. ζ potential showed that more Wu15 could adhere to the surface of modified biochar due to the existence of electrostatic interaction, so the Wu15 adsorption capacity of BC1Ca8 and BC1Ca8Mg2 increased by 10.37% and 11.1%, respectively. According to the analysis, the pseudo-second-order kinetic and Langmuir models can better fit the adsorption of Wu15 on biochar, indicating that there is a chemical reaction of electron gain and loss and the adsorption process of Wu15 by biochar belongs to monolayer adsorption. Compared with the control group, the soil exchange sodium percentage and electrical conductivity decreased by 53.6% and 46.7%, respectively, while the soil organic matter and available phosphorus increased by 25.94% and 13.85 times, respectively. In addition, BC1Ca8Mg2-Wu15 significantly improved the growth of peas because of the salt resistance of extracellular polymeric substance and the ion-exchange performance of modified biochar-based bacteria. This paper provides an effective strategy for improving saline–alkali soil and promoting sustainable agricultural development.