Walnut branch biochar base fertilizer soil remediation agent and preparation method and application thereof

The invention relates to the technical field of fertilizers, in particular to a walnut branch biochar base fertilizer soil remediation agent and a preparation method and application thereof. The preparation method of the walnut branch biochar base fertilizer soil remediation agent comprises the following steps of: carbonizing walnut branches under an anaerobic condition to obtain walnut branch biochar, mixing and crystallizing the dispersed biochar and dispersed nano Fe3O4 to obtain Fe3O4 (at) biochar modified biochar, and finally attaching microbial colonies for treating soil heavy metal pollution to the modified biochar. At the moment, heavy metal ions in the soil are adsorbed through biochar and Fe3O4, and pollutants are converted and degraded through the metabolic action of microbial bacteria. Waste utilization of walnut branches is achieved, a system for degrading pollutants is formed by biochar, Fe3O4 and microorganisms, and soil heavy metal pollution is treated through the combined action of biochar, F